utah guidance for performance, application, design ... · distribution system. the distribution...

UtahGuidanceforPerformance,Application,Design,Operation&Maintenance

PressureDistributionSystems

RevisedDraft

December2017

UtahOn-SiteWastewaterTreatmentTrainingProgramUtahWaterResearchLaboratoryUtahStateUniversityLogan,UT84322-8200

PressureDistributionSystems–Utah,2017

TableofContents

Introduction.......................................................................................................................11.0 SystemComponents/ProcessSummary.................................................................3

Figure1:Majorcomponentsofatypicalpressuredistributionsystem......................3Table1:Majorcomponentsofatypicalpressuredistributionsystem........................4

1.1. SepticTank............................................................................................................5Figure2:Typicalseptictankandpumpchamber........................................................5Table2:Septictankrequirements...............................................................................6Table3:Materialsusedforwatertightness...............................................................7

1.2. OutletEffluentFilter.............................................................................................7Table4:Effluentfilterperformancerequirements......................................................8

1.3 PumpTanks,VaultsandBasins.............................................................................8PumpTanks........................................................................................................8Table5:Pumptankrequirements...............................................................................9

PumpVaults.....................................................................................................10Table6:Pumpvaultrequirements............................................................................11

PumpBasins.....................................................................................................11Table7:Pumpbasindesignissues............................................................................12

1.4. Pumps,DosingOptions,Controls,Fittings,andValves.......................................12Pumps..............................................................................................................12Table8:Pumprequirements.....................................................................................13

PumpPerformanceCurve................................................................................13Figure3:Examplesofpumpcurves...........................................................................14

DosingOptions.................................................................................................14DemandDosing................................................................................................14TimedDosing...................................................................................................15Controls............................................................................................................16Table9:Controlssystemrequirements.....................................................................17

Fittings..............................................................................................................17Valves...............................................................................................................17Table10:Typesofvalvesandtheiruses...................................................................19

1.5. Floats(orOtherTypesofLiquidSensors)............................................................191.6. ForceMain..........................................................................................................201.7. Manifold..............................................................................................................20

Figure4A:Pressuredistributiondrainfield(slopingground).....................................21Figure4B:Pressuredistributiondrainfield(slopingground).....................................22Figure5:Pressuredrainfieldteetotee.....................................................................22Figure6:Pressuredrainfieldcrossconstruction........................................................23Figure7A:Drainfieldcontrolbox(slopingground,manifoldbelowlaterals)...........23Figure7B:Drainfieldcontrolbox(slopingground,manifoldabovelaterals)...........24Table11:Possiblemanifoldconfigurations..............................................................26

1.8. Laterals................................................................................................................26LateralSpacing.................................................................................................26LateralOrifices.................................................................................................27Table12:Lateralorificepositions.............................................................................28

LateralOrificeDiameters.................................................................................28Table13:Lateralorificediameters...........................................................................28

ResidualPressure(Head)Requirements..........................................................29Table14:Residualpressure(head)...........................................................................29

LateralOrificeFlowRate..................................................................................29Table15:Flowratecalculations................................................................................30

LateralOrificeShields.......................................................................................30Figure8:Orificecapsandshields..............................................................................31

CleanoutandMonitoringofLaterals................................................................31Figure9A:Cleanoutport...........................................................................................31Figure9B:Cleanoutport(example)...........................................................................32Table16:Cleanoutandmonitoringoflaterals..........................................................33

2.0 PressureDistributionDesignforSpecialConditions..............................................352.1. FreezingConditions.............................................................................................35

Table17:Recommendationsforfreezingconditions................................................362.2. SlopingSites.........................................................................................................36

3.0 PressureDistributionDesignProcess....................................................................39Table18:Designsteps...............................................................................................55Figure10:Systemandpumpperformancecurves....................................................55

4.0 PressureDistributionDesignSubmittalRequirements..........................................575.0 TestingandInspectionofPressureDistributionSystemafterInstallation.............59

Timed-dosetesting...........................................................................................60Post-inspectionfollow-up.................................................................................61

6.0 OperationandMaintenance(O&M)Criteria&Recommendations........................63Permitrequirements........................................................................................63Maintenancerequirements..............................................................................63

AppendixA:PressurizedDistributionDesignWorksheet.................................................65AbsorptionAreaDesign....................................................................................65PressureNetworkDesign.................................................................................66SystemPerformanceCurveWorksheet............................................................77

AppendixB......................................................................................................................79GraphB-1A:Minimumlateraldiameterfor1/8"orifices..........................................79GraphB-1B:Minimumlateraldiameterfor1/8"orifices..........................................80GraphB-2A:Minimumlateraldiameterfor5/32"orifices........................................81GraphB-2B:Minimumlateraldiameterfor5/32"orifices........................................82GraphB-3A:Minimumlateraldiameterfor3/16"orifices........................................83GraphB-3B:Minimumlateraldiameterfor3/16"orifices........................................84GraphB-4A:Minimumlateraldiameterfor1/4"orifices..........................................85GraphB-4B:Minimumlateraldiameterfor1/4"orifices..........................................86TableB-5:Orificeflowrates......................................................................................87TableB-6:Frictionalheadlossper100feetofsolidpipe..........................................88TableB-7:Frictionallossesthroughplasticfittings...................................................89TableB-8:Voidvolumeforvariousdiameterpipes...................................................89


1

Introduction

Gravityflowisafrequentlyusedmethodfordistributingeffluent.Itisalsothesimplest.Itallowswastewatertoflowbygravitythroughlargediameterpipesintoasubsurfacesoilabsorptionfield.Distributionisusuallylocalizedinafewareaswithinthefield,whichresultsinoverloadingoftheinfiltrativesurfaceinthoseareasuntilamaturebiomatdevelops.Thedisadvantageofthismethodisthatoverloadingcanleadtogroundwatercontaminationincoarsegranularsoilsduetoinsufficienttreatment,ortomorerapidclogginginfiner-texturedsoils.

Pressuredistribution,ontheotherhand,isamethodusedtoapplyeffluentuniformlyoveranentireabsorptionarea.Eachsquarefootofaninfiltrativesurfacereceivesapproximatelythesameamountperdose.Therateofdistributionislessthanthereceivingcapacityofthesoilormedia.

Theadvantagetopressuredistributionisthatinsoil-basedoralternative(mound,andpackedbed)on-sitesystems,treatmentperformanceisimprovedbymaintainingverticalunsaturatedflow.Infiner-texturedsoilsormediathedegreeofcloggingisreduced.

Researchevidenceindicatesthatwastewatertravelingverticallythrough2to4feetofsuitable,unsaturatedsoilprovidesadequatetreatmentofthewastewater.Researchalsoindicatesthatthemethodofdistributionofseptictankeffluentwithinthesoilabsorptionfield,mound,orpackedbedsystemwillaffectthetreatmentperformanceofthesystem.

Pressuredistributionisusuallyusedinlocationswhereitiseitherdesirableorrequiredto:

• Achieveuniformapplicationofwastewaterthroughoutasoilabsorptionfieldorontheinfiltrativesurfaceofpressurizedalternativesystems,includingmoundorpackedbedsystems

• Treatanddisperseeffluenthigherinthesoilprofile

• Improvethetreatmentperformanceandextendthelifeexpectancyofasoilabsorptionfield,amound,orapackedbedsystem

Apressuredistributionsystemconsistsof:

• Aseptictanktoseparatethemajorsolidmaterialsfromtherawwastewaterenteringthetank

• Ascreeningdevicetoprotectthepumpanddistributionlateralorificesfromsolids

• Ameanstodeliverspecifieddosesofeffluent,underpressure,tothedistributionsystem.Thedistributionsystemconsistsofsmall(typically1to2inchesindiameter,basedonhydrauliccalculations)lateralswithsmalldischargeorifices.Apressureheadiscreatedwithinthelaterals,usuallybymeansofapump

2

AsregulatedbyUtahAdministrativeCodeR317-4,pressuredistributionisapplicabletoanysystemthatusessoilasatreatmentmediumwherepressuredistributionmayimprovelong-termperformanceofthosesystems.

Pressuredistributionisarequiredcomponentofalternativesystemsthatincludethemoundsystemandpackedbedsystems.ItisalsoappropriateforlargersoilabsorptionandpackedbedsystemsthatareregulatedbyUtahAdministrativeCodeR317-5.


3

1.0 SystemComponents/ProcessSummary

Pressuredistributionsystemsrequirethefollowingbasiccomponents:

CONTROLPANEL

SEPTICTANK

PUMPCHAMBER

PRESSUREDISTRIBUTIONLATERALS

CLEANOUT/MONITORINGPORTS

FORCEMAIN

ACCESSRISER

MANIFOLDPIPE

Figure1:Majorcomponentsofatypicalpressuredistributionsystem

Component: Primaryfunction:

Septictank Solidsseparationandstorage.

Effluentfilter Protectionofpumpanddistributionnetworkorificesfromsolids.

Pumpchamber Transportofaspecificvolumeofeffluentfromthepumpchambertothedistributionnetwork.

Accumulateeffluentbetweenpumpcyclesandduringmalfunction.

Forcemain(transportpipe)

Pipelinethatconnectsthepumptothemanifold.

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Component: Primaryfunction:

Manifold Pipingnetworkconnectingtheforcemaintothevariouslaterals.

ControlPanel NEMA-ratedboxcontainingallthecontrolsforthepumpingsystem,dosecyclecounter,pumpruntimemeter,andalarmcontrols.

Laterals Smalldiameterpipeswithorificesthatdistributeeffluentovertheinfiltrativesurfaceofanabsorptionarea.

Absorptiontreatmentarea

Nativesoilorotherreceivingmediawherevariousbiologicalandphysicalprocessesprovideadditionaltreatmentofseptictankeffluent;Consistsofasoilabsorptionfieldortheinfiltrativesurfaceofamoundorpackedbedsystem.

Table1:Majorcomponentsofatypicalpressuredistributionsystem


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1.1. SepticTank

Apressuredistributionsystemmustbeprecededbyaproperlysizedseptictank:

Figure2:Typicalseptictankandpumpchamber

TheseptictankmustbedesignedincompliancewiththeguidelinesgiveninUtahAdministrativeCodeR317-4.

24” DIAMETER ACCESS RISER

FINISH GRADE

SECURED LID WITH GAS TIGHT SEAL

SEDIMENTS

FLOATING MATFROM SEWAGE SOURCE

TO PUMP CHAMBER

APPROVED EFFLUENT

FILTER

24” DIAMETER ACCESS RISER

FIGURE 2

PUMP CHAMBER (TYPICAL)

SEPTIC TANK (TYPICAL)

SEDIMENTS

WORKING VOLUME

EMERGENCY STORAGE

NORMAL TIMER OFF LEVEL

HIGH WATER ALARM LEVEL

ENCLOSED PUMP SEDIMENT SHROUD *

INDEPENDENT FLOAT STEM FOR FLOAT MOUNTING

FROM SEPTIC TANK

FINISH GRADE

SUBMERSIBLE CENTRIFUGAL

PUMP

CHECK VALVE *

ANTI SIPHON VALVE *

THREADED UNION

SERVICE VALVE *

SECURED LID WITH GAS TIGHT SEAL

TO DRAINFIELD

18”

* AS NEEDED

SLUDGE

SLUDGE SCREEN

SLUDGE

OPTIONAL

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Allseptictanksshould:

Septictankmust: Requirement:

Betestedforwatertightness

Bewatertighttoalevelaboveanypossibleseasonalgroundwater.EachtankmustbetestedforwatertightnessaccordingtotheproceduresoutlinedinUtahAdministrativeCodeR317-4.

Retainsolids Havefunctioningoutletbaffleortees.Mayincludescreeningoftheeffluentwithaneffluentfilterthatislocatedintheseptictankorinaseparatepumpchamber.Screeningaroundthepumpinapumpvaultcanalsobeusedtoprotectthepump;howeveralsousinganeffluentfilterintheseptictankcanprovideextraprotection.

Beaccessible Haveserviceaccessmanholesandmonitoringportsfortheinletandoutlet.

Havewatertightrisersthatmeetrequirements

Risersmustbeplacedtofacilitatepumpingbothsidesofthetank.Multiplerisersmaybenecessary.

Coversmustbegasketedandsecurelyfastenedbyscrewsorsomeotherlockablemeans.

Risersmustbeconstructedofdurable,structurallysoundmaterialsanddesignedtowithstandexpectedphysicalloadsandcorrosiveforces.

Ifsoilcoverismorethan24inches,risersmustextendtowithin6inchesofthesurfaceoftheground.Therisershouldpreferablybebroughtuptothefinishedgradetoencourageperiodicservicingandmaintenance.

Table2:Septictankrequirements


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Someorallofthefollowingmaterialscanbeusedtoaidinachievingwatertightnessofthetanks:

Material: Use:

Cast-in-placeflexiblerubbergaskets

Usedforinletandoutletopeningswithstainlesssteelclampstosealtherubbertothepipes.

Flexiblerubbergaskets Sealtotheinletandoutletopeningswitharatchetedexpansionsealandstainlesssteelclamps.

Expandinggroutmaterial Usedtosealtanksandrisers.Somegroutswillshrinkandcrackovertimeandthusallowtankstoleakafterthetankisbackfilled.

Bentonitebackfill Usedaroundthetankseamsandpipeentrancestohelpprovideawatertighttank.

Epoxy Anothereffectivemethodofsealingsomekindsofjoints,buttheweatherconditionsmustbeidealandthereisnocapacityforflex.

Rubbergrommets Usedaroundsmallerinletanddischargepipes,conduitandjunctionboxpenetrations,canbeeffectiveincontrollingleaks.

Table3:Materialsusedforwatertightness

1.2. OutletEffluentFilter

Aneffluentfilterorscreenisaremovable,cleanabledeviceinstalledontheoutletpipingofaseptictankforthepurposeofretainingsolidslargerthanaspecificsize(1/8inchorgreater)and/ormodulatingtheeffluentflowrateoutofthetank.

Theeffluentfiltershouldprovideanopenareaflowcapacityatleastequaltotheflowcapacityprovidedbya4-inchdiameterPVCpipe.However,usingtheminimumareawillverylikelyrequireahighfrequencyofcleaning.Instandardpracticeamuchlargerflowareashouldbeused.Largerflowareaswillresultinlongerintervalsbetweenservicesforthesamehydraulicandorganicstrengthloadings.

Aneffluentfilterisrequiredinallpressuredistributionsystems.

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Theeffluentfiltershouldmeetthefollowingperformancecriteria:

Function: Filtermust:

Positioning Drawliquidfromthe“clearzone”oftheseptictank.

Durability Beconstructedofdurable,non-corrodingmaterials.

Besecurelyfastenedtopreventdislodgingormisalignment.

Protection Preventdischargeorificesfrompluggingbyparticleslargerthantheorifices.

Protecttheeffluentpumpfromdamageduetoparticlesthatexceedthepump’scapacitytopass(maybeanissuewithsometypesofpumps).

Service Avoidlossofperformancebetweenroutineserviceevents.

Shouldnotrequirefrequentroutineservicing.

Bedesigned,constructedandinstalledforeasyandthoroughcleaning.

Haveanaccessriserforcleaningovertheseptictankopeningabovetheeffluentfilter.Thetypicalconcreteriserandlidcommonontanksthatareburiedbelowfinishedgradearenotacceptableforextendingtothesurface.Theyarenotwatertightandwillnotkeepodorsandgaseswithinthetank.Althoughconcretelidsareheavy,theyarenotnecessarilyheavyenoughtokeepchildrenoutofaseptictank.

Table4:Effluentfilterperformancerequirements

1.3. PumpTanks,Vaults,andBasins

PumpTanks

Apumptankisachamberusedtohousethepump,floats,andmiscellaneousequipmentrequiredforthepumpingsystem.Pumptanksreceivingseptictankeffluentwillaccumulatesludgeandscum.Thesludgelevelshouldnotbeallowedtoaccumulatetolevelsabovetheintakeofthepump.


9

Pumptankmust: Requirement:

Bestructurallysound

Bewatertighttoalevelaboveanypossibleseasonalgroundwater.

Leaktestingisrequired.

Beequippedwithawatertightriserwithasecuredlidthatextendstothegroundsurface.

Lidsmustbeequippedwithanairtightgaskettoeliminatenuisanceodorsandbesecuredfromaccidentalorintentionalremovalbyunauthorizedpersons,especiallychildren.

Havesufficientinternalvolumeofthepumpchamber

Designmustaccommodate:

Theoperatingvolume.

Deadspacebelowthepumpinlettoprovideforfulltimepumpsubmergenceandtoensurethatthepumpintakeisaboveaccumulatedsludgelevels.

Emergencystoragevolumeforperiodsofpoweroutage,mechanicalfailure,orequipmentmalfunctions.Thismaybeachievedbyrelyingonthefullvolumeoftheseptictankandpumptank(uptothebottomofthelids),providedthattheelevationofthetopofthehighestlidisbelowthelowestfloordraininthebuildingservedbythesepticsystemtopreventbackupintothebuilding.Reductionsinemergencypumpchambervolumemaybeconsideredwhen"duplex"orredundantpumpsareused.

Time-dosedsystemsmayrequireadditionalsurgetankcapacity.

Surgevolumemaybeaconcernfortime-dosedsystemsthatmayperiodicallyexperiencehigherinfluentflowratesintothepumptankthandischargeflowratesfromthepumptank.

Failuretosizethetankforsurgeflowscouldresultinnuisancehighlevelalarms,leadingtotheneedtouseshortertimersettingstoaccommodateperiodsofhighflow.

Usingshortertimesettingsduringsurgeflowconditionssimulatesademanddosingconfigurationandlimitsthebenefitsofatimed-dosingsystem.

Table5:Pumptankrequirements

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PumpVaults

Pumpvaultsmaybeusedtohousethepumpingequipmentwithinaseptictank,apumptankorapumpbasin.Apumpvaultusuallyconsistsofeitherone(Simplex)ortwo(Duplex)pumps,dischargeassembly(ies),filterorscreensaroundthepump(s),afloatswitchassembly,andafloatstembracket.

Pumpvaultmust: Requirement:

Beaccessible Thepumpvaultmustbedesignedandconstructedtofacilitateremovalandmaintenanceofthevaultscreen,pumps,andfloats.

Haveadequatevolume

Theminimumstorageandpumpworkingvolumesintheseptictankmustbeequivalenttothevolumerequiredinaseptictank.Theminimumvolumesinclude:

• Sufficientvolumetohandlethefunctionsofaseptictankandtokeepthepumpsubmerged,whenrequired

• Additionalreservestorageforemergencysituationsasappropriateforprotectionofpublichealthandtheenvironment.

Notinterferewiththeseptictank

Ifapumpvaultisinstalledwithinaseptictankthevaultmustnotinterferewiththemainfunctionoftheseptictank,whichistoprovidefortheseparationofscumandsettleablesolids.

Theuseoftwocompartmentseptictanksisrecommendedalthoughnotrequiredwhenapumpvaultisused.

Topreventinterference,thepumpvaultshouldbeinstalledsuchthat:

• Theentrypointofthewastewaterintothepumpvaultisattheleveloftheclarifiedeffluentinthemiddleofthetank.Theelevationofthepumpvaultisbasedonthetankdimensionsandthemaximumallowablelevelsofscumandsludgebeforethetankrequirespumping

• Theliquidlevelchangescausedbyoperationofthepumpsystemareminimizedtoreducethedisturbanceofthescumlayer.Thischangewillgenerallybelessthantwoinches,butmayvarydependingonthespecifictankdimensions

• Theamountofwastewaterpumpedoutofthetankduringeachdosingeventisequaltotherequireddosevolume.Whentheinfluentflowratetemporarilyexceedstheeffluentflowrateduringa24hourperiod,surgevolumeisrequiredtoaccommodatethesetemporaryhighflowperiods


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Pumpvaultmust: Requirement:• Timer-basedpumpcontrolsystemsmayalsorequiresurgevolume

capacityinthetank

• Thepumpingrateshouldalwaysbelessthan30gallonsperminute,andpreferablylessthan20gallonsperminute.Ifhigherpumpingratesarerequired,thepumpingsystemshouldbeinstalledinaseparatepumptankaftertheseptictankandnotinapumpvaultintheseptictank

• Reservevolumemustbeprovidedwithintheseptictankforemergencystorageintheeventofapoweroutageormechanicalfailure.Thereservevolumemaybeachievedbyrelyingonthefullvolumeoftheseptictank(uptothebottomofthelid),providedthattheelevationofthetopofthelidisbelowthelowestfloordraininthebuildingservedbytheseptictank,toensurethatbackupintothebuildingdoesnotoccurduringemergencyevents

• Thepumpvaultmustnotinterferewiththepumpingofsolidsfromthetank.Ifthepumpingvaultaccessriseristhesameaccessriserusedforpumpingofsolidsandscumfromthetank,thepumpvaultandtheassociatedpumpingequipmentshouldbeinstalledsothattheycanbeeasilyremovedwhenthetankisbeingpumped.Preferablytheseptictankshouldhaveotheraccessopeningsforsolidsremoval.

Table6:Pumpvaultrequirements

PumpBasins

Apumpbasinisaseparatepumpingchamberlocatedwithinapackedbedsystemorafterapackedbedsystem.Becausewastewateristime-dosedintoapackedbedsystem,demanddosingfromthepumpbasinafterthepackedbedsystemcanbeusedbecausetheamountofflowforpumpingwillbecontrolledbythetimed-dosingoftheeffluenttothepackedbedsystem.

Apumpbasinmayalsobeusedtolifteffluentfromaseptictanktoagravity-flowabsorptionfieldortoanat-gradesystem.Demanddosingmayalsobeusedinothersituations,ifthedesignisapprovedbytheregulatoryauthority.

Pumpbasinissues: Considerations:

Volume Apumpbasinhaslittletonostoragevolumeandmustbeusedonlyindemanddosing.

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Pumpbasinissues: Considerations:

Off-lineprovisions Thedesignermustaccountforperiodswhenthepumpisoff-linebyconsideringcorrectiveactionresponsetimesandactivities.

Iftherewillbeabackuporoverflowconditioncreatedduringapoweroutageoramechanicalfailure,andiftheflowscannotbestoppedorminimizeduntiltheproblemiscorrected,apumpbasinwithmorestoragevolumeshouldbeused.

However,ifthefacilitygeneratingtheflowscanbeclosedorothertemporaryarrangementsmadetoreducewastewaterflow,orifadrinkingwaterpumpcanalsonotbeusedduringapoweroutage,thenapumpbasinwithlittleemergencystoragevolumecanbeused.

Table7:Pumpbasindesignissues

1.4. Pumps,DosingOptions,Controls,Fittings,andValves

Pumps

Theeffluentpumpsusedforpressurizingthedistributionnetworksareeithercentrifugaleffluentpumpsorturbineeffluentpumps,whichareslightlymodifiedwellpumps.Thecentrifugalpumpisahighercapacity/lowerheadpumpwitharelativelyflatperformancecurveandtheturbinepumpisalowercapacity/higherheadpumpwitharelativelysteepperformancecurve.Turbinepumpsprobablyhavealongerlife.Theymaybethepreferredchoicefortimedosingbecauseoftheirlongevityrelativetostop/starts.

Pumpsandpumpinstallationsmustmeetthefollowingrequirements:

Requirement: Pumpmust:

Pumpeffectively Beabletopumpeffluentscontainingsolidsupto1/8inchindiameterwhenfollowinganeffluentfilter,andsolidsupto1/2inchindiameterwhenaneffluentfilterisnotused.

Becapableofmeetingtheminimumdesignhydraulicflowandheadrequirementsoftheproposedpressuredistributionsystem.

Pumpsmustbeabletowithstandthewet,corrosiveenvironmentfoundwithinthepumpchamber,vault,orbasin.Onlypumpsthatarespecifiedforuseinwastewatershouldbeused.


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Requirement: Pumpmust:

Beaccessible Pumpsmustbeinstalledsothattheycanbeeasilyremovedand/orreplacedfromthegroundsurface.

Undernocircumstancesshouldpumpreplacementand/orrepairrequireservicepersonneltoenterthepumptank.

Pumpsmustbefittedwithunions,valves,andelectricalconnectionsnecessaryforeasypumpremoval,servicing,andrepair.

Haveaprotectivefilter

Pumpsmustbeprotectedbyanapprovedoutleteffluentfilterinthechamberprecedingthepumpchamberorbypumpscreens,asdescribedinprevioussections.

Complywithelectricalrequirements

Pumpsandassociatedcontrolsshouldhavegas-tightjunctionboxesorsplicesandhaveelectricaldisconnects(asperNationalElectricCode)appropriatefortheinstallation.

Theboxesshouldbeplacedsothattheydonotinterferewiththeservicingand/orremovalofothercomponentsinstalledinthesystem.

Pumpsandelectricalhook-upsmustconformtoallstateandlocalelectricalcodes.

Dependingonthesizeofthesystemand/orlocationofthepumpingequipment,specializedequipmentforexplosionmayberequiredbyfirecodes.Theappropriateregulatoryauthoritywilldeterminewhetherspecializedequipmentisrequired.

Table8:Pumprequirements

PumpPerformanceCurve

Apumpperformancecurveisagraphicalrepresentationthatdescribestherelationshipbetweenflowrateandheadforaspecificmodelofpump(Figure3).Thebottomaxisislabeled“gallonsperminute”,andtheleftsideislabeled“totaldynamichead”.ThesevaluesarecalculatedinthePressureDistributionDesignProcess(section3.0ofthismanual).Theflowrateandtotaldynamicheadneededtooperateaspecificpressurizeddistributionsystemisnotedbyapointonaspecificpumpperformancecurvethatrepresentsthecombinationofflowrateandheadatwhichthesystemmustperform.Thispointshouldbeonthepumpperformancecurveorjustbelowthecurve.Ifthepointisaboutthecurve,adifferentpumpmustbeselected.

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Figure3:Examplesofpumpcurves

DosingOptions

Therearetwodifferentoptionsfordeliveringdosesofeffluenttothereceivingcomponentofapressurizeddistributionsystem:demanddosingandtimed-dosing.

DemandDosing

Indemanddosing,thedoseisdeliveredtothereceivingcomponentwheneveradosevolumeaccumulatesinthepumpchamber.Theeffluentisnotmeteredoutuniformlyovera24-hourperiod.

Demanddosingistheleastcomplexmethodofdosingandthereforeleastcostlytoinstallandeasiesttounderstand.

Demanddosingisnotsensitivetoheavyusedaysandthereforewillnotactivatethealarmcircuitwithweekendguests,largelaundrydaysorparties.

Additionally,demanddosingdoesnotprotectthesoilabsorptionfield,moundorpackedbedsystemfromhydraulicsurgesandoverload.

Effluentdistributionisbasedonthepatternofwateruseintheparticularsystem.Forexample,inresidentialsystems,mostoftheeffluentisdistributedduringtheperiodsofhouseholdwateruse,thatis,usuallyinmorning,eveningandweekendsurges.

Whendemanddosingisused,thedosevolumesshouldbeminimizedtoprovidesmallerandmorefrequentdosestothesystem,withlargedosesavoidedasmuchaspossible.


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TimedDosing

Intimeddosing,theeffluentismeteredtothereceivingcomponentindiscrete,evenlyspaceddoses.

Thismethodofdosingallowsmorefrequent,smallerdosestobepumpedtothereceivingcomponent,therebypromotingunsaturatedflowthroughthesoilorfiltermediawhileprotectingthereceivingcomponentfromhydraulicoverload.

Timeddosingisstronglyrecommendedonallpressuredistributionsystems,forthistypeofsystemenhancesperformanceandreliability.

Timeddosingmeansthatboththelengthofeachdose(whichdeterminesthegallonsperdose)andtheintervalbetweendoses(whichdeterminesthenumberofdosesperday)iscontrolledbyatimingdevicewheneveradosevolumeisinthepumpchamber.

Thenumberofpumpcyclesshouldbeadjustableandinsufficientnumbertomeetthedesignneedsofthesystem.

However,timeddosingissensitivetoheavyusedaysandthereforethehighwateralarmmaybeactivatedwhenthevolumeofwastewaterexceedsthedesignflow.Somecausesofexcessiveflowareweekendguests,largelaundrydays,parties,leakingfixtures,andgroundwaterleakingintotheseptictankorpumpchamber.

Withtimeddosing,dosevolumespumpedtothereceivingcomponentareoftensmallerandmorefrequent,withinterveningrestingandaerationperiods,therebyassuringunsaturatedflowthroughthesoilorfiltermedia.Thesesmallerdosesmayrequiresmallerorifices,smallertransportandlateralpipes,checkvalves,andorificesinthe12o'clockpositiontomaintainthesystemfullofeffluentbetweendoses.

Whentimed-dosingisused,thetimersettingsshouldbesetsuchthatthesystemdosesequalamountsofeffluentevenlyduringthedaybydelivering12to24dosesperday.Somesystemsmayevenbedosed100to200timesina24-hourperiod,resultinginimprovedtreatmentperformance.Thetimersettingsshouldbesetsothatnomorethanthedailydesignflowisdeliveredtotheinfiltrativeserviceduringa24-hourperiod.

Surgeanalysisisespeciallyimportantwhentimed-dosingisused,thatis,whenmanysmalldosesarebeingappliedovertime.Enoughsurgevolumeisrequiredtoavoidhighlevelalarmsduringtheshortduration,higherflowsthatarecommonlyobservedinthemorningsandeveningsinresidentialapplications.

Timeddosingisnotrequiredforpressuredistributionsoilabsorptionfieldsfollowingtreatmentcomponentsthataretimed-dosed.Theflowisalreadytime-dosedtothetreatmentcomponent,andthereforethepumpchamberafterthetreatmentcomponentmaybedemand-dosed.

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Controls

Forallpumpingsystems,theappropriatecontrolssystemmustbespecified.Thecontrolssystemmusthavetheproperfunctionalityfortheproposeddesign.

Requirement: Controlssystemmust:

MeetCodeandsafetyrequirements

Meettheapplicablecoderequirementsfortheinstalledlocation.ThismayincludeNEMA4,orNEMA4X,orotherstandardsdependingonwherethecontrolsaremounted.

BeUnderwritersLaboratories(UL)listedorotheracceptedequivalent.

Functionality Deliverprescribeddosesuniformlytotheorificesinthedistributionnetwork.

Havecontrolslocatedwithinsightofthepumpingsystem.Wherethisisnotpossible,itmaybenecessarytoprovideelectricaldisconnects.Thelocalelectricalcodesshouldbeconsultedforspecificrequirements.

Havedefaultsettingsfortimed-dosecontrolstoassurethattheflowsdonotexceedthemaximumdesigncapacitywithoutenteringalarmcondition.

Recordandstorepumpruntimesandnumberofpumpingeventsusingbuiltincyclecountersandelapsedtimemeters.Awatermetermayalsobeusedtotrackandrecordsystemflows.

Shouldnotbeinstalleddirectlytotheoutsidewallofthehouseorstructurewherethesystemmaycreatenuisancecomplaints.Thecontactmotorswitchingsoundmaytransferthroughthewallandcreatenuisancecomplaints.Noisecanbereducedbymountingthecontrolsonapostnexttothewallofthestructureorbyinstallingthecontrolsonthegarageornon-bedroomwalls.

Alarms Provideanaudiblealarm.Theaudiblealarmmayhaveasilencingswitch.

Provideavisiblealarm.Thismustcontinuetoshowuntiltheconditioniscorrected.

Providearemotealarminaconspicuousplaceforsystemswherethealarmconditionmaygoundetected.

Thealarmcircuitmustbeindependentofthepumpcircuit,


17

Requirement: Controlssystemmust:includingaseparatebreakerfromthehousesupply.Thisistoensurethatanalarmsoundsifthepumpbreakerorthebreakersupplyingpowertothecontrolpanelistripped.Thedesignermustclearlyspecifythisrequirementinthedesigndocumentationandtheinspectorsmustcheckforthisseparatealarmcircuit.

Table9:Controlssystemrequirements

Fittings

Pipefittingsincludetherangeofcomponentsthatareusedtoconnectpipeendsforin-line,multi-port,offsetandmountingconfigurations.

Pipefittingcrosssectionsaremostly,butnotalways,circularinshapetomatchwiththepipesectionwithwhichtheyareconnected.

Pipefittingsareusedforvariouspurposes.Theycanbeusedtoextendorterminatepiperuns,changeapipe'sdirection,toconnecttwoormorepipesandtochangethepipesize.

Theamountoffrictionlossassociatedwithfittingsmustbeaccountedforinthedesignofthepressuredistributionsystem.

Adischargeassemblyiscomposedofallofthepipingandfittingsbetweenthepointofpumpdischargetothepointatwhichtheforcemainexitsthetank.Thefrictionlossassociatedwiththedischargeassemblyisacriticalcomponentofsystemdesignandmustbeaccountedforinsystemdesign.

Valves

Valvesaremechanicaldevicesusedtocloseoff,regulate,ordiverttheflowoffluids,includingliquidsandgases.

Valvetype: Uses:

Checkvalve Acheckallowsflowinonlyonedirectionbyclosingwhentheflowdirectionreverses.

Commonusesofcheckvalvesinonsitesystemsaretokeeptheforcemainpipefromdrainingbetweendoses,andinduplexpumpingapplications.

Whentheforcemainpipeisnotallowedtodrain,acheckvalveshouldbeinstalledjustabovethepumpinthedischargepiping.Thiswillincreasethepumpingefficiency,asalltheeffluentpumpedwillbedischargedtothepumpingchamberwithoutreturningaportionattheendofeachcycle.

Incoldweatherinstallationstheforcemainpipewithacheckvalvemustbeinstalledbelowthefrostdepthorinsulatedtopreventfreezing.

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Valvetype: Uses:Duplexpumpingsystemsareoftenusedorrequiredonlargerornon-residentialapplicationstoprovidepumpredundancy.Duplexpumpsareusuallyconnectedintoasinglesupplyorforcemainpipe.Eachpumpmusthaveacheckvalveinstalledsothatwhenapumpisoperational,theeffluentdoesnotdischargeintothetankthroughtheotherpump.Thecheckvalveshouldbelocatedasclosetothepumpaspossible.

Whenaduplexpumpsystemisinstalledinacoldweatherapplicationwithdrainback,thedrainbackorificemustbelocatedabovethecheckvalvesothatthepipecandrainbetweendosecycles.

Acheckvalvewillrequiremaintenanceandthereforeshouldbeinstalledsothatitcanberemovedforservicingorreplacement.

Unionsplacedatthecheckvalveareacommonmeanstoallowservicingofthecheckvalveswhileavoidingdestroyingofthevalve.Somecheckvalvescanbedisassembledwithoutremovingthemfromtheline.Ifpossible,checkvalvesshouldbeinstalledsuchthattheyareaccessiblefromthesurface.

Thelocationofcheckvalvesmustbewelldocumentedandmarked.Preferablycheckvalvesshouldbelocatedinastructurethatisaccessiblefromthesurface.

Air/vacuumvalve

Air/vacuumvalvesreleaseairbuildupwithinthepipeaswellasletairintothepipetopreventasiphonorvacuumcondition.

Theyareneededwhenpipesareinstalledtopumpoverahillandbackdowntheothersidetoanopendischargepoint.

Therearemultipleoptionsforlocationoftheair/vacuumvalve.Itisofteninstalledatthehighpointofthesystem.However,insmallerresidentialsystems,itcanbeinstalledinthedischargeassemblywithinthepumpaccessriser.Theair/vacuumvalvewillopenandallowairtoenterthesystemunderavacuumconditioncreatedwhentheeffluentdrainsdownthebacksideofthehill,releasingthevacuumwithinthepipe.Theopeningofthevalvewillalsostopthevacuumfromsiphoningeffluentfromthepumptank.

Forlargersystems,theair/vacuumvalveshouldbeinstalledatthehighpointofthepipesystem.Forinstallationswheretheelevationdropfromthehighpointtothelowpointissignificant,thevacuumwithinthepipecouldresultincollapseofthepipewithoutanair/vacuumvalve.Whenthisisaconcern,thedesignershouldspecifythatthevalvemustbelocatedatthehighpointandnotinthedischargetank.


19

Valvetype: Uses:

Airreleasevalve

Airreleasevalvesonlyletairbuildupoutofthepipe.

Theyareusedwherethereisahighpointinthepipingthatcanaccumulateairandgasbuildup.

Theairreleasevalveisasimplervalvethantheair/vacuumcombinationvalve.Whenthedownhillsideofthepipingsystemwillremainfullandthereisnoriskofdrainingthatwouldcreateavacuumwithinthepipe,anairreleasevalveisadequatetoreleaseanybuildupofairwithinthepipe.

Vacuumreleasevalve

Vacuumreleasevalvesonlyallowairintothepipe,andwhileunderpressuretheyareclosed.Theyareusedmostoftenindripdispersalsystemstoimmediatelyreleasethevacuumafterthepumpshutsoff.

Theyareinstalledatthehighpointofthesystem.Vacuumreleasevalvesopenwhenthepumpshutoffs,releasingvacuumanddecreasingpotentialforpullingsoilintothetubing.

Table10:Typesofvalvesandtheiruses

1.5. Floats(orOtherTypesofLiquidSensors)

Afloatisasensorinstalledinapumpvault,chamber,orbasinthatopensorclosesanelectricalcircuitinresponsetochangingliquidlevels,therebycontrollingequipmentoperation.

Floatsinstalledinapumpingsystemshouldnotbeinstalledonthepumpdischargepiping.Theyshouldbeinstalledonaseparatepipeormechanism(forexample,afloattree,whichisaremovabledevicelocatedwithinapumpvaultorpumptanktowhichfloatsareattached)sothattheycanbeeasilyremovedforservicing,adjustment,andmaintenancewithoutremovingthepump.

Theminimumrequirementsfortimedpumpcyclecontrolsareatimeractuatorfloatforthepumpandahighliquidlevelalarm.

Inaddition,alowliquidlevelofffloatishighlyrecommended.

Forpumpchambersservingsingle-familyresidences,thenecessaryfloatsorliquidlevelsensorsaretoactuateandturnoffthepumpcontrolsystem,andahighwateralarmfloat.

Redundant“off”controlsareoptional,butarehighlyrecommendedandmayberequiredbytheregulatoryauthority.

Commercialandmulti-familyapplicationsmayrequireredundant“off”andspecialratingsoninstalledmotorsandequipment.

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1.6. ForceMain

Theforcemain(maintransportpipe)mustbesizedbasedonhydrauliccalculationsforflow(gallonsperminute)andtotalhead(infeet)fortheproposedlayout.

Wherepotentialforfreezingexists,thelinemustbeburiedbelowthefrostdepth,insulated,orinstalledwithdrainbackorificessuchthatthewaterdoesnotremaininthepipebetweendoses.

Whenthedrainbackoptionisused,thesmallestacceptablediameterofpipeshouldbeselectedtoincreasethepumpingefficiencyandminimizeunnecessarypumpingofeffluent.

Wheneverapumpisusedtopumpeffluenttoanelevationlowerthanthepump,pumpfittings,orforcemain,anair/vacuumreleaseorsimilaranti-siphondevicemustbeinstalledtopreventsiphoning.

1.7. Manifold

Theprimaryfunctionofthemanifoldistodeliverequalflowtoalllateralswhileminimizingsystemfrictionlosses.

Themostcommonconfigurationsarethecenterandtheendmanifolds.

Endmanifoldsmaybeusedwhenthesystemutilizesshortlaterals,butcentermanifoldsallowforuseofsmallerlateralpipesizes.

Thelateralsmaybeconnectedtothemanifoldinseveralways.Manifoldtolateralconnectionmustbeappropriateforthesiteconditionsandthespecificuse.

Manifolddesignsforslopingsitesareparticularlycritical.Lateralsatdifferentelevationswillhavedifferentresidualpressures,withthelowestlateralhavingthehighestresidual.Inaddition,ifthemanifoldisnotdesignedcorrectly,thelowestlateralwillreceivepressurebeforethetoplateralandsystembackflowwillcontinuetothelowerlateralsafterthepumpingcyclehasended.Inthisinstance,thelowesttrenchwillreceivemoreflowthantheothers,withthepotentialforoverload.Whiletheremaybeseveralsolutionstotheseproblems,Figures4Aand4Billustratetwomethodsforresolvingthem.ThecheckvalvesandflowcontrolvalvesshowninFigures7Aand7Bareassumedtobeanintegralpartofthemanifold.


21

LEGEND

LOCATEVALVECONTROLBOXATELEVATIONBELOWLOWEST

LATERALSERVED

FEATURES:

1. FLOWISCONTROLLEDTOEACHLATERALBYFLOWCONTROLVALVE

2. BACKFLOWISPREVENTEDBYCHECKVALVEONEACHLATERALFEEDERPIPE

3. PIPINGABOVECHECKVALVESISALWAYSFLOODED.LENGTHANDVOLUMEOFLATERALSORLATERALFEEDERPIPESDOESNOTIMPACTSIZEOFDOSE.

CHECKVALVE FLOWCONTROL VALVE

FORCEMAINFROMPUMPCHAMBER

LATERALFEEDERPIPES

HEADERMANIFOLDPIPE


DOWNSLOPEGRADIENT

Figure4A:Pressuredistributiondrainfield(slopingground)

22

HEADERMANIFOLDPIPE


LATERALFEEDERPIPES

DOWNSLOPE

GRADIENT


LEGEND


FEATURES:

1. FLOWISCONTROLLEDTOEACHLATERALBYFLOWCONTROLVALVE

2. BACKFLOWISPREVENTEDBYMANIFOLDPOSITIONABOVELATERALS

3. ACCEPTABLEVARIANCEOFDOSETOEACHLATERALMAYBEIMPOSSIBLEDUETODIFFERINGVOLUMESWITHINEACHOFTHELATERALFEEDERPIPES,ALLOFWHICHDRAINAFTERPUMPCYCLE

Figure4B:Pressuredistributiondrainfield(slopingground)

ORIFICES

FROMPUMP

CHECKVALVE(OPTIONAL)

MANIFOLDINSTALLEDBELOWFREEZINGDEPTHFLOWCONTROLVALVE

THREADEDPLUGORCAP

LEGEND


Figure5:Pressuredrainfieldteetotee


23

ORIFICES

FROMPUMP

CHECKVALVE(OPTIONAL)

THREADEDCAPORPLUG

FLOWCONTROLVALVE

LEGEND


Figure6:Pressuredrainfieldcrossconstruction

TODRAINFIELDPRESSURELATERALS

A A

RISERWITHLOCKINGLID

FLAPCHECKVALVE

FLOWCONTROLVALVE

LONGSWEEP90DEGREEELBOW


WASHEDROCKDRAINSUMP

SECTIONA-A

SLOTSASREQUIRED

Figure7A:Drainfieldcontrolbox(slopingground,manifoldbelowlaterals)

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A A

TODRAINFIELDPRESSURELATERALS

RISERWITHLOCKINGLID

FLOWCONTROLVALVE

LONGSWEEP90DEGREEELBOW


WASHEDROCKDRAINSUMP

SECTIONA-A

SLOTSASREQUIRED

Figure7B:Drainfieldcontrolbox(slopingground,manifoldabovelaterals)

Examplesofpossiblemanifoldconfigurationsaregivenbelow.Otherconfigurationsthanthosedescribedmayalsobeused.

Configuration: Uses:

Headermanifoldwithcheckvalves

Aheadermanifoldispositionedatanelevationbelowthelaterals(Figure4A),withcheckvalves,flowcontrolvalvesandfeederlinestoeachlateral.

Thisconfigurationwillmaintainthemanifold,feederlinesandlateralsfullbetweendoses,willnotallowdrainback,andcanbeadjustedatonelocationtoequalizeresidualheadinalllaterals.

Thisarrangementcandeliversmallvolumesperdose,allowingmanydosesperday,ifdesired.

Cautionshouldbetakentominimizethepotentialforeffluentfreezinginthelateralsandmanifold.


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Headermanifoldwithoutcheckvalves

Aheadermanifoldisplacedatanelevationabovethelaterals(Figure4B)withoutcheckvalves,withflowcontrolvalvesandfeederlinestoeachlateral.

Themeasuredflowsfromanorificeineachlateralarenearlyequalwithouttheuseofcheckvalvesandwithoutmaintainingthesystemfullbetweendoses.

Tee-to-teewithmanifoldbelow

Tee-to-Teewithmanifoldbelow(Figure5)-Whenfreezingandslopingsiteconditionsarenotaconcern,thismethodofconstructioncanbeusedtoallowaveryrapidpressurizationofthesystem,especiallyifthetransportlineremainsfullbetweendoses.

Whencheckvalvesareusedinthemanifoldjustdownstreamofeachlateral,themanifold(andlateralstoo,whenorificesareinthe12o'clockposition)staysfullofeffluentbetweendoses.

Withthislayout:

• Thereisnodrainbackfromtheupperlateralsandmanifoldintothelowerlateral

• Thesystemiscompletelychargedwithinjustasecondortwoafterthepumpisturnedon

• Thesystemcanbedosedwithverysmallvolumesperdose.

Crossconstruction Crossconstruction(Figure6)-Ifthelateralorificesaredrilledinthe6o'clockposition,thisdesignwillallowthelateralsandaportionofthemanifoldtodrainbetweendoses,assumingthetransportlineremainsfullbetweendoses.

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Tee-to-teewithmanifoldabove

Ifthelateralorificesaredrilledinthe6o'clockposition,theentiredistributionnetworkwilldrainaftereachdose.

Thismaybedesirableonaslopingsite(wherecheckvalvesarenotinstalledinthemanifold),topreventupperlateralsfromdrainingbackthroughthemanifoldtothelowermostlaterals,therebyoverloadingthem.

Iftheorificesaredrilledinthe12o'clockposition,thelateralswillremainfullbetweendoses.Thismaybedesirablewhentheobjectiveistopressurizethedistributionnetworkquicklywithouttheuseofcheckvalves.

Cautionshouldbetakentominimizethepotentialforeffluentfreezinginthelaterals.

Table11:Possiblemanifoldconfigurations

1.8. Laterals

Lateralsareperforatedpipesusedtodelivereffluentequallyovertheinfiltrativesurfaceofthepressuredistributionsystem.

LateralSpacing

Uniformdistributionofeffluentisaccomplishedthroughlateralspacingandorificespacing.Thefollowingminimumspacingoforificesandlateralsisrecommended:

1orifice/6sq.ft.-Mounds

1orifice/4sq.ft.-Intermittentsandfilter

1orifice/4sq.ft.orless-Recirculatingsandfilter,Recirculatinggravelfilter,Textilefilter

Closerorificespacingshouldbeconsideredforusewhensmalldosesarespecifiedandwheretheinfiltrativesurfaceisinhighlystructuredsoilsorhaslargemacropores.

Forpressurizeddrainfields,eachtrenchwillusuallyhaveasinglelateral.Inthiscase,itisrecommendedthattheorificesbeasclosetoeachotherasispractical,preferablyoneorificeevery2to4feet,oncenter.

Orificespacingisalsousedtodeterminethemaximumspacingbetweentheoutsidelateralsandtheedgeofthetrenchorbed,whichis1/2oftheselectedorificespacing,±0.5feet.


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LateralOrifices

Orifices(holesinthelateralsofaspecifieddiameter)areacriticalelementofasuccessfulpressurizeddistributionsystem.Theyareusedtodeliverequalamountsofeffluentoveragivenarea.

Caremustbegiventohowtheorificesaredrilledinthepipe.Evenwithagooddesign,useofadulldrillbitandasloppyprocessfordrillingtheholescanleadtoafailedinspectionbytheregulatoryauthorityorunequaldistributionofeffluentthroughthesystem.

Orificesshouldbedrilledinamanufacturingsettingsothattheholesarelinedupcorrectlyandarecleanandfreefromdebris.Additionally,theorificesmustbedrilledwithaproperlysized,sharpdrillbit.Accurateholediametersmayalsorequiretheuseofjigsorotherdrillstabilizingtoolstopreventwobbleandtodrilltheholeperpendiculartothepipe.Properlayoutandcontrolwillensurethatthecorrectnumbersoforificesareactuallydrilledineachlateral.

Orificescanbedrilledinthetopofthepipe(12o'clockposition)orinthebottomofthepipe(6o’clockposition).

Orificeposition: Considerations:

12o’clockupposition Orificesdrilledinthe12o’clockpositionwillmaintainthelateralsfullorpartiallyfullandthereforereducetheamountofeffluentneededtopressurizethesystem.

Maintainingeffluentinthelineswillpromotebiologicalgrowth,whichmayacceleratecloggingoftheorificesandbuildupofsludgeandslimeinthelines.Italsomakesthelateralssubjecttofreezinginareaswherethisisaconcern.

Thelateralsmaybedrainedbyputtingafeworificesinthe6o’clockposition,orbydesigningthesystemssuchthattheforcemainandlateralsdrainbacktothesurgetank.However,thesepracticeswillincreasethedosevolumerequired.

Whenusinggravellesschamberswithpressuredistribution,theorificesmustbeorientedinthe12o’clockposition.Ifoneortwoorificesareplacedinthe6o’clockpositiontofacilitatedrainingaftereachpumpcycle(topreventfreezinginareasofthestatewherethatmayoccurortopreventbuild-upofmicrobialgrowthinsidethelaterals),theymusthavesomemechanismtobreaktheflow(anorificeshieldthatdrains,apadofgravel,etc.).

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Orificeposition: Considerations:

6o’clockdownposition

Whensomeoralloftheorificesareinthe6o’clock,or"down"position,thelateralswilldrainbetweendosecycles,thusretardingbiologicalgrowthandreducingfreezeuppotential.

Althoughsystemswithsomeoralloftheorificesinthe“down”positionmaybelesspronetoclogging,theyalsowillrequirealargerdosevolumetopressurizethesystem,duetolateralsdrainingbetweenpumpcycles.

Table12:Lateralorificepositions

LateralOrificeDiameters

Ingeneral,smallerorificesarepreferredforonsitesystems.

Theminimumorificediameteris1/8inch.Largerorificesmaybeused,butcautionshouldbeusedwhendesigningsystemswithlargerorifices.Theywillincreaseflowrates,thusrequiringtheuseoflargerpipesandlargerpumps.Largerpipesandpumpsincreasetheinitialcostofthesystemandresultinsystemsthataremoreexpensivetooperate.

Thefollowingorificediametersaresuggested:

Orificediameter: Uses:

1/8inch Usedinallalternativesystems&pressurizedtrenches

5/32inch Typicallyusedinpressurizedtrenches

3/16inch Usedinmoundsorpressurizedtrenches

1/4inch Canbeusedinmounds(butgenerallynotrecommendedforuse)

Table13:Lateralorificediameters


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ResidualPressure(Head)Requirements

Residualpressuresaredeterminedbymeasuringsquirtheight,thatis,theheightachievedbytheliquidinapressurizedlateralwhenanorificeispositionedsuchthatthedischargeisverticalintotheatmosphere,typicallyexpressedinfeetofheight.

Thefollowingresidualpressuresarerecommended,basedonorificediameters:

Orificediameter: Residualpressure:

1/8inch 3to5ft

5/32inch 2to4ft

3/16inch 2to3.5ft

1/4inch 2to2.5ft

Table14:Residualpressure(head)

LateralOrificeFlowRate

Theactualflowratefromeachorificeisrepresentedbytheequation:

Qo=11.79d2h0.5

where:

Qo istheorificeflowingallonsperminute

d istheorificediameterininches

h isthedischargeheadinfeet(alsocalledresidualpressureorhead)

Thereareotherfactorsthataffectaccuratecalculationoftheorificeflowrate,suchasaccuratedrillingofholes,classofpipe,sizeofpipe,andslightvariationsinthefrictioncoefficientsusedforfittings.

Thechoiceofcoefficienttouseinadesigncanvary,dependingontheexperienceofthedesignerinbeingabletopredictaccuratelyandcontrolforthefrictionlossesandothervariablesofconstructionandmanufacture.Thetwomostcommoncoefficientsusedare11.79and12.38.

Formanydesigns,experiencehasshownthatuseofaslightlyhighercoefficientintheequationmoreaccuratelypredictstheactualflow.

Forwhichevercoefficientisselected,itiscriticallyimportantthatthesamecoefficientbeusedthroughoutthedesign.

30

Examplesoforificeflowratesingallonsperminute(gpm),using11.79asthecoefficient,include:

Orificediameter: Squirt: Flowrate:

1/8inch 5ft 0.41gpm

5/32inch 3.5ft 0.54gpm



Table15:Flowratecalculations

LateralOrificeShields

Orificeshieldsaredevicesusedtoprotectorificesfromexternalblockagesandtodeflectthesquirtoverawidersurfacearea,thusspreadingtheeffluentovermoreoftheinfiltrativesurface.

Theuseofshieldsisrecommended,evenwhenthesystemisinstalledingravel,andespeciallywhenorificesareorientedinthe12o-clockposition.Theshieldsmustbestrongenoughtowithstandtheweightofthebackfillandlargeenoughtoprotecttheorificefrombeingpluggedbypiecesofgravel.

Orificeshieldsmaybethehalfpipedesign,thelocalcaptype,oranotherdesignthataccomplishesthesameendresult(Figure8).


31

Pressure line in 6" PVC 1/2 shell braced to prevent line shifting.

Cover Soil

Lateral Gravel

6" PVC cut in half

Pressure line suspended per manufacturer specifications. Orifices must be oriented in the 12:00 position

Chamber Lateral

Cover Soil

Pressure line to be cross braced to prevent line shifting. Orifices must be oriented in the 12:00 position

Lateral

Cover Soil

Chamber

Orifice covered by 2”- 6" PVC pipe cut in 1/2

Cover Soil

Gravel

Orifice with Cap Trench Detail

Orifice capLateral

Cover Soil

Gravel



Original Ground Surface



Original Ground Surface Original Ground Surface

Gravelless Trench Detail Gravelless Trench Detail

Lateral Orifice shield

Figure8:Orificecapsandshields

CleanoutandMonitoringofLaterals

Alllateralsmusthaveaccessforcleanoutsandmonitoringportstothelateralendsfromthegroundsurface,suchasthroughasmalllandscapingbox(Figures9Aand9B).Designsmustincludedetailsofmonitoringandcleanoutportsandexplainhowtheyaccomplishtherespectivetasks.

METERBOXOROTHERENCLOSURE

BACKFILL

MEDIA

ORIFICESHIELD

THREADEDCAP

LATERAL

Figure9A:Cleanoutport

32

THREADEDCAPORPLUG

PLUGINSLEEVE 6"PVC

LASTORIFICE;WITHORIFICESHIELDSIFORIFICEORIENTATIONISUPWARD

PRESSURELATERALASSPECIFIED

DRAINROCK;6"MIN.BELOWPIPE

6"PVCWITHDRAINHOLES;EXTENDTOBOTTOMOFGRAVELTOMONITORPONDING

UNDISTURBEDSOIL

PVCHOSEORLONGSWEEPELBOW

BACKFILLMATERIAL

INFILTRATIVESURFACE

VALVE(OPTIONAL)

Figure9B:Cleanoutport(example)

Components: Considerationsforcleanoutandmonitoring:

Lateralaccess Somelocalhealthdepartmentshavespecificrequirementsforlateralaccess.Thedesignershouldconsultwiththelocalpermittingauthorityandspecifytheappropriatefittingsinthedesign.Theaccessboxshouldbelargeenoughtoallowaccesstocaps,plugs,orvalveswithhands,tools,etc.

Wideswingfittings Lateralsmusthavewideswingfittingstowardsthesurfacefortheinstallationsofapipebrushorothermaintenancetools.

Theuseoftwo45-degreeelbowsorwidesweeping90-degreeelbowsatthelateralendsisrecommended.

Plugorcap Theendsmusthaveaplugorcapthatiseasilyremovedformaintenanceandformonitoringlateralresidualpressure(squirtheight).


33

Components: Considerationsforcleanoutandmonitoring:

Monitoringports Monitoringportsshouldbeopenandslottedatthebottomandbevoidofgraveltotheinfiltrativesurfacetoallowvisualmonitoringofpossiblestandingwaterontheinfiltrativesurface.

Shutoffvalve Ashutoffvalveisofteninstalledatthelateralends.

Insomecases,theremayalsobeashutoffvalvelocatedatthebeginningofthelaterals.Thismaybedoneintheindividualtrenchorinavalvebox.

Thebenefitofinstallingthevalvesontheinletsideofthelateralsistofacilitatemaintenanceandtroubleshootingandtoassistincontrollingflowsonslopingsites.Theydoincreasetheoverallcostofthesystemandarenotmandatory.

Table16:Cleanoutandmonitoringoflaterals


35

2.0 PressureDistributionDesignforSpecialConditions

Specialcaremustbetakenwhendesigningpressuredistributionsystemsforuseunderfreezingconditionsoronslopingsites.

2.1. FreezingConditions

ManylocationsinUtahhavefreezingconditionsduringthewintermonths.Dependingonthespecificlocation,thefrostdepthcanrangefromafewinchestoseveralfeet.Trafficareasandareasthatareclearofsnowwillhavedeeperfrostdepthsthanareaswithgoodsnowcover.

Alldesignsinstalledinfreezingconditionsrequireproperdesignandengineeringtoensurethatthesystemdoesnotfreeze.Thefollowingrecommendationsareprovidedasaguidetoassistthedesigner.

Recommendation: Considerations:

Avoidstandingwater

Oneofthebestprotectionsagainstfreezingisdesigningthesystemsothatitdoesnotholdstandingwaterforprolongedperiodsoftime.Thisisusuallyaccomplishedwithdrainbackholesinpipeinthepumpingtank.Thepipingsystemshouldbeinstalledwiththeappropriateslopebacktothepumptankandadequatebeddingtopreventsaggingofthepipe,whichcouldresultineffluentaccumulatingandfreezingintheareaofsagging.

Theorificesinthelateralsshouldalsobeinstalledfordrainageaftereachdose.Forsystemswiththeorificesinstalledpointingdownward,drainageshouldoccurnaturally.Orificeshieldsshouldbeusedtokeeptheorificesclearandfreetodrainaftereachdoseevent.

Lateralsmaybeinstalledwithorificespointingupward(12o’clockposition)providedthatthereareseveralorificespointingdownward(6o’clockposition).Dependingonthesizeofthesystem,adequatedrainagemaybeaccomplishedwiththefirst,middleandlastorificepointeddownward.Longerlateralsmayrequiremoredownwardpointingorificestoensuredrainageaftereachcycle.

Installbelowfrostdepth

Deeperburialisespeciallyrecommendedforsystemsthathavealongforcemainorforsystemswithlargerpipediametersthatrequiremorevolumeofwatertofillthesystem.

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Recommendation: Considerations:

Insulate Pipingthatisinstalledwithinthefrostdepthandthatmayretainwatermustbeinsulated.

Insulationmustbeadequatefortheappropriatefrostdepth.

Whererigidinsulationboardistobeusedaboveaninstalledpipe,itmustextendbeyondeachsidetoprotectthepipefromfreezing.

Manifoldposition Installingthemanifoldatthehighpointinthesystemmayalsobehelpfulincoldweatherinstallations.

Thisconfigurationwillalloweffluentinthetransportpipeandsomeoftheeffluentinthemanifoldtodrainbacktothepumptank.Theremainingwaterinthemanifoldandthelateralswouldthendrainintothereceivingsystem.

Thisdesigncanbeaccomplishedwiththeuseofverticallymountedteesinthemanifoldandlateralpiping.

Withsystemsthatareveryshallow,withinthefrostdepth,suchasashallowdripdispersalsystem,themanifoldshouldbeinstalledbelowthedriptubingatadeeperdepthtoprotectagainstfreezing.

Heating Althoughaheatingsystem(heattape,lightbulbs,etc.)maybedesignedtomaintaintemperaturealongthepipes,thisdesignisusuallynotrecommended.

Table17:Recommendationsforfreezingconditions

2.2. SlopingSites

Slopingsitescanbechallengingforbothgravityandpressurizeddistributionsystems.Oneofthemainconcernsismakingsurethattheslopingsitereceivesequalamountsofeffluentthroughouttheabsorptionarea.Specifically,lowerareasshouldnotreceivemoreeffluentthantheupperareas,resultinginoverloadingorsurfacingofeffluent.

Oneofthemostcommonmethodsfordosingmultipletrenchesonslopingsitesisthedropboxmethodofserialdistribution.Withserialdistribution,theuppertrenchreachesasaturatedconditionbeforeoverflowingtothelowertrenches.Withpumpingtothehighpointofthesystem,asimplemanifoldorsplittermechanismcanbeinstalledthatwillequallysplittheflowintoequalvolumesthatcanbedirectedtotheindividualtrenches.

Ifapumpisrequiredtolifttheeffluenttothehigherelevationoftheabsorptiontrenches,thepumpingsystemcouldalsobeusedtopressurizetheentiredistributionsystemoflaterals.Researchhasshownthatequaldistributionovertheentireinfiltrativearea


37

promotesimprovedperformanceofthesystem,alongerlifeofthesystem,andbettertreatmentoftheeffluent.

Wherepressurizedtrenchesareinstalledonaslopingsite,thesystemmustbesizedtolifttheeffluenttothehighestpointandmeettherequiredsquirtheight.Whenlateralsareinstalledatvaryingelevations,thelowertrenchesmaydischargeeffluentathigherflowrates,anddependingonthedifferenceinelevation,thelowertrenchescanbeeasilyoverloaded.

Thereareseveralmethodsforadjustingdistributionofeffluenttothedifferentelevationsoflaterals.

• Valvesatthebeginningofthelateralsmaybeused,withgatevalveslesslikelytochangeduetosystemcycling

• Pipediametersmaybeadjustedtoequalizeflowsatthedifferentelevations

• Flowcontroldiscsmayalsobeused.However,itmaybedifficulttocalculatethecorrectsizeoforificesforthediscstoensurethatequaldistributionbetweentrenchesoccurs.Additionally,constructionchangesinelevationwillrequirerecalculationoftheflowcontroldiscorificesizes

• Deliveringtheeffluenttothehighpointofthesystem(Figure4B)willminimizeoverloadingofthetrenchesbecausetheeffluentfromtheuppertrenchescannotdraintothelowertrenches.


39

3.0 PressureDistributionDesignProcess

Thepressurizeddistributionsystemmustbesizedappropriatelyforthedesignflowsofthesystem.

Criticaldesignflowsthatwillaffecttheappropriatedesignforaparticularsystemincludethedailydesignflowandtheoperationaldesignflow.Operationaldesignflowsareafunctionoftheproposeddistributionsystem.Therearemanycorrectdesignapproachesforaparticularsituation,providedthatsomesimpledesignstepsarefollowed.

Overall,thedesignflowandthetotaldynamicheadarecalculatedandusedtodesignthecriticalcomponentsofapressurizeddistributionsystem.Thedesignflowistheestimatedvolumeofwastewaterperunitoftimeforwhichthesystemisdesigned,andthetotaldynamicheadisthemeasureofthecumulativeenergythatapumpmustimparttoaliquidtomoveitfromonepointtoanother,consistingofthesumoffrictionhead(asbaseduponpipingdiameter,systemconfiguration,andflowrate)andthestatichead(thesumofelevationheadandoperatingpressure).

ManypumpandonsitesystemmanufacturersoffersoftwarethatwillperformthedesigncalculationsforthedesignerusingthehydraulicequationsandthehydraulicperformancesoftheirparticularsystemcomponentsthataregivenintheDesignWorksheet.

Tofacilitatetheappropriatedesignapproach,thePressurizedDistributionDesignWorksheetinAppendixAmaybeused.AsummaryoftheWorksheetdesignprocessisincludedinthissection,withsupplementalexplanationsforeachstep.

40

Designstep: Discussion:

Step1:

Determinethedailyflowrate

Thedailyflowrateisthemaximumflowofwastewaterthatthesystemwillreceiveina24-hourperiod.

Onsitewastewatersystemsforsingle-familyresidencesusingconventionalabsorptionsystemsaresizedbasedonthenumberofbedroomsinthehome.Inpressurizedsystems,thedailydesignflowisdefinedasgallonsperdaydistributedthroughthesystem.

Additionally,thedesignflowratemustalsobedetermined.Thedesignflowrateisnotthesameasthedailydesignflowbutistheflowrateofthepumpingsystemwhileinoperation.

Thedailydesignflowforpackedbedsystems,accordingtoUtahAdministrativeCodeR317-4,isestimatedas300gallonsperday(gpd)forthefirsttwobedrooms,plusanadditional100gpdforeachadditionalbedroom.Absorptionsystemsandmoundsystemsaredesignedusing150gpd/bedroom.

Forsystemsotherthansingle-familyresidences,thedailyflowrateisdeterminedusingtheproceduresoutlinedinUtahAdministrativeCodeR317-4.

Forpressurizedsystems,flowpatternsthroughoutthedayandparticularlythroughouttheweekcanbeanimportantconsiderationinsystemdesign.Theuseofasurgeorequalizationtankmayberequiredtohandlepeakflows.


41


Step2:

Determinethemaximumloadingrate

Theloadingrateisdefinedastherateatwhichthewastewaterisappliedontotheabsorptiontreatmentarea.

Forpressurizedtrenchesforresidentialandnon-residentialsystems,selecttheloadingrateusingguidancefromR317-4.

ForthealternativewastewatertreatmentsystemsdefinedinUtahAdministrativeCodeR317-4,themaximumloadingrateisbasedontheparticulartreatmenttechnology:

• Moundsystems=1.0gal/sq.ft./day

• Intermittentsandfilter:Sandmedia=1.0gal/sq.ft./day;Sandfill=1.2gal/sq.ft./day

• Recirculatingsandfilter=5.0gal/sq.ft./day

• Recirculatinggravelfilter=15.0gal/sq.ft./day

• Textilefilter=30gal/sq.ft./day

• Peatfilter=5.0gal/sq.ft./day

• Syntheticpolystyrenemediafilter=21gal/sq.ft./day

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Step3:

Determinetherequiredabsorptiontreatmentarea

Therequiredabsorptiontreatmentareaisspecifictothetreatmentmediumthatreceivesthewastewater.

1)Forpressurizedtrenchesinsystemswithoutpretreatmentofeffluentsinpackedbedsystems,therequiredsizeoftheabsorptiontreatmentareaisdeterminedusingthesizingtableinR317-4.

2)Whenpressurizedtrenchsystemsareusedtodisperseeffluentfrompackedbedsystems,theymaybereducedinsizeaccordingtotheguidelinesgiveninR317-4.

3)Inmoundsystems,theabsorptiontreatmentareaisthegravelbedinwhichthedistributionpipesareplaced.

FormoundsystemstherequiredtreatmentareaisdefinedasAxB,whereA=absorptionareawidthandB=absorptionarealength.

4)Forapackedbedsystem,thetreatmentareaisthesurfaceareaofthesystem.Thetreatmentareamayconsistofsand,gravel,textile,orpeat,dependingonthetypeofpackedbedsystem.

Thedailydesignflowisusedtodeterminetherequiredareaformounds,packedbedsystems,andpressurizedtrenchesfornon-residentialsystems.Theminimumrequiredsurfaceareaiscalculatedusingthefollowingequation:

MinimumRequiredSurfaceArea=DailyFlowRate,gpd(Step1)/MaximumLoadingRate,gpd/sq.ft(Step2)

Step4:

Sketchthedimensionsofthetreatmentareafromsite-specificinformationobtainedfromthesiteevaluationprocess

Theconfigurationandsizeofthesoiltreatment/infiltrativesurfaceisdependentonthesoilandsitecriteriaandlimitationsofthespecificsite.Oncethedimensionshavebeenestablished,thedistributionnetworkcanbedesigned.


43


Step5:

Selecttheorificediameter

Theorificediameterwilldirectlyimpactthedesignflowrate.Largerorificeswillresultinlargerflowratesperorifice,evenwithalowersquirtheight.

Historically,largerorificeswererecommendedasaresultofconcernsthatwastewaterwouldeitherplugorificeswithsolids,and/orgrowthontheinsideofthepipewouldplugtheorifices.Pressurizeddesignsthatuselowheadpumpswillnotbeabletodeliverthenecessarypressureevenifonlyminimalpluggingoccurs.However,routinemaintenanceofthesystempreventscloggingproblems.Additionally,usingsmallerorificesoftenoffsetstheconcernofpluggingoforificesbecausesmallerorificesallowsmallerdoses,whichimprovesthelifeandperformanceofthesystem.

Guidelinesfortheselectionoforificediametersinclude:

• 1/8inchorificesareacceptableforanyoftheapprovedalternativewastewatersystems.

• 5/32inchorificesaretypicallyusedforpressurizeddrainfieldtrenches.

• 3/16inchorificescanbeusedinmounds,especiallywhenlowheadpumpsareinstalled.

• 1/4inchorlargerorificesarenotrecommendedformostonsitesystems.

Step6:

Selectthesquirtheight

Thesquirtheightrecommendationsweredevelopedtoensurethatthesystemwilldosethecorrectamounteachcycleandtominimizecleaningoftheorifices.

Thefollowingsquirtheightsarerecommendedbasedonorificediameter:

• 1/8inchorifice=3ft.to5ft.

• 5/32inchorifice=2ft.to4ft.

• 3/16inch=2ft.to3.5ft.

• ¼inch=2.5ft.

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Step7:

Determinetheorificeflowrate

Theorificeflowratecancalculatedusingthefollowingequation:

Q=11.79*d2*(h)½

Where:

Q=Orificeflowrate,gpm

d=Orificediameter,inches

h=Squirtheight,ft.

Anothercommonlyusedcoefficientusedinsteadof11.79is12.38.

Usingtheaboveequationwith11.79asthecoefficient,thefollowingflowratescorrespondtotheorificediametersasfollows:

1/8inchorificewith5ft.squirt=0.41gpm

5/32inchorificewith3.5ft.squirt=0.54gpm



AdditionalflowratesfororificediametersandsquirtheightsaregiveninAppendixB,TableB-5:Orificeflowrates.


45


Step8:

Selecttheorificespacing

Orificespacingdeterminestheapplicationrateoveragivensurfacearea.

Fortrenches,theorificespacingwilllikelybegreaterthanformoundsandpackedbedsystems.However,thedesignershouldspacetheorificesasclosetogetheraspracticaltoprovideequalloadingthroughouttheentiresystem.Mosttrenchdesignswillhaveanorificeevery2feetto4feetalongthepressurizedlateral.

Formoundsandpackedbedsystems,theorificespacingshouldbesettoprovideforequaldistributionwithintheareaofinfluenceofeachorifice.Theproperapplicationofthisprinciplewillresultinsquareareasofinfluence,thatis,equalorclosetoequalspacingbetweentheorificesandthelaterals.

Theserecommendationsareprovidedasaguideforsettingthespacingforeachtypeofalternativesystem:

1orifice/6sq.ftformoundsystems

1orifice/4sq.ftforintermittentsandfiltersystems

1orifice/4sq.ft.orlessforrecirculatingsandfiltersystems

1orifice/4sq.ft.orlessforrecirculatinggravelfiltersystems

1orifice/2sq.ft.fortextilesystems

Forpressurizedtrenches,orificesaretypicallyplacedevery2to4feetalongeachpressurizedlateral.

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Step9:

Determinethenumberandlengthoflaterals

Thenumberandlengthoflateralsaredependentonthespaceavailableforthesystemandaresite-specific.UsingthesketchofthesystemcreatedinStep4andtheorificespacing,thedesignershouldselectlateralplacementthatpromotesequaldistribution.

Whenmultiplelateralsareusedwithinthesameinfiltrativesurface,thelateralsandorificesshouldbeplacedtoprovideequilateraldistribution(equalspacingofthelateralsandorifices)oftheeffluent.

Thenumberoflateralsisallofthelateralsinthesystem.Thenumberoflateralsdosedbypumpisthenumberoflateralsdosedwhenthepumpruns.Itisthesameasallofthelateralswhenzonesarenotused.Itisthenumberoflateralswithinthezonewhenzonesareused.ThisnumberisusedfordeterminingthedesignflowrateofthepumpinStep14.

Lateralsshouldextendtowithin6inchesto1footoftheendoftheabsorptionarea.

Thedistancefromthelateralstotheedgeoftheinfiltrativeareashouldbe6inchesto1footforbedareasand1footto1.5feetfortrenches.

Step10:

Determinethenumberoforificesineachlateral

Thenumberoforificesineachlateralisafunctionoftheorificespacingandthelaterallength.

Thefollowingequationshouldbeusedtodeterminethenumberoforificesineachlateral.

Numberoforifices=(laterallength/orificespacing)+1

Afractionremainingasaresultofthecalculationisaccountedforbydisregardingthefractionandaddinganadditionalorifice.

Step11:

Determinethelateralflowrate

Theorificeflowrateismultipliedbythetotalnumberoforificesinalateraltodeterminethelateralflowrate.Thefollowingequationisused:

(Orificeflowrate)x(Numberoforifices)=Lateralflowrate(gpm)

Thelateralflowrateistheamountofwaterneededtoprovideeachorificewiththeflownecessarytoprovidethedesignsquirtheight.


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Step12:

Determinethelateralpipediameter

Lateralsizingisacriticalstepinthedesignprocess.Failuretosizethelateralcorrectlycanresultinunevendistribution.

Thelateralsmustbesizedlargeenoughtoprovideflowsthatareequalthroughoutthelengthofthelateral.

Theorificesatthebeginningofapressurizedlateralwilldischargeatahigherratethanattheendofthesamelateral.Theproperlysizedlateralwillminimizethisdifferencetopromoteequaldistribution.

Themaximumdifferencebetweenthefirstandlastlateralorificeshouldbelessthan10%oftheorificeflowrate,or21%ofthesquirtheight.

Thefollowingtablegivestheactualsquirtheightdistancescorrespondingtoa10%flowdifferenceforselectedsquirtheights:

ResidualSquirtHeight 10%FlowDifference 2feet 5inches 2.5feet 6.3inches 3feet 7.6inches 3.5feet 8.8inches 4feet 10inches 5feet 12.6inchesGraphsB-1toB-8inAppendixBareusedtoselecttheappropriatelateralpipediametersize.Selectionoftheappropriategraphisdependentontheorificesizing:

1/8inchorifices UseGraphB-1orB-2




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Step13:

Determinethelateralheadloss

Therearemultiplemethodsfordeterminingtheheadlosswithineachlateral.Simplifiedmethodsproduceresultsaccurateenoughforonsitesystems.

Thetwomethodsdescribedbelowallowanapproximatesolutionwithouttheuseofmorecomplexhydrauliccalculations.Othermethodsmaybeacceptableprovidedthatadequateinformationisprovidedforthereviewingauthoritytoverifythedesign.

Method1:Use1/3ofthesquirtheight(inft.)selectedinStep6.Thiswillusuallybeaconservativeapproach,providedthattheotherstepsareeachfollowedcorrectly.

Method2:Calculatetheheadlossbasedonasolidpipe1/3ofthelengthoftheperforatedlateralpipedeterminedinStep9usingAppendixBTableB-6:Frictionalheadlossper100feetofsolidpipe.Thisapproachisconservativewhencomparedtotheactualheadlosseswithintheperforatedpipe.

Step14:

Determinethedesignflowrate

Thedesignflowrateingallonsperminute(gpm)isthecombinedlateralflowforallofthelateralsthataredosedatagiventime.

Forthetypicalsingle-familysystem,thedesignflowratewillusuallybetheflowfromallofthelateralsinthesystem.Forlargersystemsthataredividedintozones,thedesignflowrateincludesallofthelateralsinazone.

NumberoflateralsxLateralflowrate=Designflowrate

Thedesignflowrateisusedinpumpselection.


49


Step15:

Determinethediameterofthemanifold

Themanifolddiametershouldbelargeenoughtosupplyflowtoallofthelaterals.

Forsmallsystems,suchasatypicalsingle-familyresidentialsystem,themanifoldmaybethesamediameterasthelaterals,oritmaybethesamesizeastheforcemainpipe.Whenthemanifoldpipelengthsarerelativelyshortcomparedtotheoverallpipelengthsusedfortheforcemain,itmaybeacceptabletosimplifythemanifoldpipesizingtospecifythatthemanifoldbethesamepipediameterastheforcemainpipe.

Forsomesystems,themanifolddiametermaybebetweenthesizeoftheforcemainandlateralpipes.

Twoacceptablesimplemethodsfordeterminingthemanifoldpipediameterare:

Method1:Usethesamediameterofpipeusedfortheforcemain.

Method2:UsetheheadlosscalculatedforthemanifoldinStep16todeterminethebestpipesizediametertobeusedforthemanifold.Becausetheflowisbeingdispersedintoeachlateralacrossthelengthofthemanifold,itisacceptabletouseaflowrateequalto½ofthedesignflowratewhencalculatingthemanifoldheadloss.Thetotalmanifoldheadlossesshouldalwaysbelessthan40%ofthetotaldynamichead(TDH),andthediametershouldbeassmallaspossible.Wherethisisnotthecase,alargerpipesizeshouldbeused.

Step16:

Determinethemanifoldpipeheadloss

Theheadlossinamanifoldpipeisthesameasforasolidpipe,suchasaforcemain.Theheadlossisafunctionoftheflowrate,thepipesizediameter,andthepipesmoothnesscoefficient(c-value).

TheHazen-Williamsequationforwatermaybeusedtodeterminethisfrictionalloss.

Tosimplifythisprocess,AppendixBTableB-6:Frictionalheadlossper100feetofsolidpipemaybeused.

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Step17:

Determinetheforcemainlength

Theforcemainlengthisthetotalpipelengthfromthepumpdischargetothebeginningofthemanifold.

Thislengthisnotthesameasthehorizontaldistancefromthepumpvaulttothedischargepoint.Thislengthissite-specificandisdeterminedforeachproposedsystemaspartoftheoverallsystemlayout.

Step18:

Determinetheforcemaindiameter

Thediameteroftheforcemainisafunctionofthedesignflowrateandtheforcemainlength.

Thedesignershouldselectthesmallestacceptablepipesizediameter,forsmallerpipediameterswillprovidehighervelocitiesduringadose.Smallerpipediameterswillalsoreducetheamountofpumpingforsystemswithdrainbackorificesthatprotectagainstfreezing.Additionally,thesmallerpipeswillfillwithwaterquickerduringadoseandwillcometopressurequicker,whichleadstofasterequaldistributionthroughoutasystem.

Thelimitingfactorinselectingsmallpipediametersistheheadlossthroughtheforcemain.

Forsmallsystemsthathaveshortforcemainlengths,thehigherheadlossperlinealfootofpipeismoreacceptablethanforasystemthathasaverylongpipelengthatthesameheadlossperlinealfoot.

Thedesignershouldalsobeawareoftheavailableheadlossthatatypicalpumphascapacitytodeliver.Forsomedesignsthisavailableheadlosswillbecritical.Otherdesignsmaybeabletoexperiencehighheadlosswithminimalimpactonpumpselection.

Oncethedesignflowrateisknownandthelengthoftheforcemainisdetermined,AppendixBTableB-6:Frictionalheadlossper100feetofsolidpipeisusedtoselectthesmallestpipesizediameterthatwillstillmaintainanacceptableoverallheadloss.

Step19:

Determinetheforcemainheadloss

TheHazen-Williamsequationforwatermaybeusedtodeterminethisfrictionalloss.

Tosimplifythisprocess,AppendixBTableB-6:Frictionalheadlossper100feetofsolidpipemaybeused.


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Step20:

Determinemiscellaneousheadlosses

Everysystemhasanumberoffittingsandvalvesthatincreasetheheadlosstothesystemasawhole.Thesefittingsandvalvesmustbeincludedinthemiscellaneousheadlosstotal.Therearetwomethodsthatcanbeusedtodeterminetheselosses:

Method1:Add50%oftheforcemainheadlosstoaccountforfittings.

Thisisaconservativeapproachformosttypical,single-familyresidentialsystems.Cautionshouldbeemployedinusingthisapproachforlargersystemsorforsystemsthathavealargenumberoffittings.Whenconcernsariseregardingtheapplicabilityofthisapproach,itisrecommendedthatMethod2beused.

Method2:Determinethe“equivalent”pipelengthsforeachofthefittingsinthedesignanduseAppendixBTableB-7:Frictionallossesthroughplasticfittingstodeterminetheheadlossassociatedwiththefittings.

Frictionalheadlossesassociatedwithaparticularfittingcanberepresentedasanequivalentpipelength.Thismethodassignsalengthofstraightpipeofthesamediameterthatequalstheheadlossthatoccursthroughthefitting.Manufactureroffittingscanprovidethisinformation.Additionally,therearetablesthatcontainthisinformationforthetypicalfittingsusedinanonsitesystem.AppendixBTableB-7:Frictionallossesthroughplasticfittingsprovidesheadlossesforsomeofthemostcommonlyusedfittings.

Thetwoexamplespresentedbelowcanbeusedasaguidefordetermininghowtobestaccountformiscellaneousheadlosses:

Example1:Asmallerforcemainpipediameterresultsingreaterheadloss.Iftheforcemainpipelengthislongandthediameterissmall,thehigherheadlossforthepipeandthelonglengthwillbothincreasetheheadlosscalculatedfortheforcemainpipe.Whenusingthe50%methodabove,itispossiblethattheheadlosscalculatedinMethod1willbemuchhigherthandesired.

Example2:Somesystemswillhaveseveralfittingsduetothesite-specificconditions.Forasystemwithmanyfittings,theuseofMethod1or2maynotaccuratelyaccountforthefittingsinthedesign.Changesmadebyacontractorduringinstallationmayalsoincreasethenumberoffittingsinaparticulardesign.Wheneitheroftheseconditionsoccurs,andifthefittingscreateheadlossabovewhatisestimated,thesystemmaynotperformasdesigned.

52

Designstep: Discussion:Amanufactured,pre-assembleddischargeassembly,whichconsistsofallpipingandpartsbetweenthepointofpumpdischargetothepointatwhichthesupplylineexitsthetankandusedtoconveyeffluentfromapumptotheexteriorofariserorpumpbasinorchamber,maybeusedinapressurizedsystem.

Whenusingamanufactureddischargeassembly,informationonheadlossthroughthedischargeassemblycanbeobtainedfromthemanufacturer.Usingthisinformationwillprovideamoreaccurateheadlossmeasurementthanusingeitherofthetwosimplifiedmethodsdescribedabove.

Step21:

Determineheadlossassociatedwithazonevalve

Iftheproposedsystemwillusemultiplezones,thenthesystemwilllikelyrequiretheuseofoneormorezonevalves.Dividingthedistributionareaintozonesisusedtomaintainareasonablysmallpumpsizewhenmanyorificesaretobedosed.Dividingthedistributionsystemintozoneswillalsodistributethehydraulicloadovertimeaswellasspace,allowingforlongerrestingtimes.

Azonevalvemaybeamechanicalrotatingvalve,asolenoidvalve,orothermechanismforcontrollingtheflowfromonezonetoanother.Thisvalvewillhaveaheadlossassociatedwiththeflowpassingthroughthevalve.

TheheadlossthroughthevalvewillbemorethantheamountaccountedforinthemiscellaneousheadlossesstepdiscussedinStep21.Therefore,whenasystemutilizesoneormorezonevalves,theheadlossforthevalve(s)mustbecalculatedandaddedtothetotalheadloss.

Themanufacturerofaspecificvalvewillhaveanequationand/orachartfordeterminingtheheadloss.Theheadlosswillbeafunctionofthevalvesizeandthedesignflowratethatwillpassthroughthevalveeachtimethesystemdoses.

Step22:

Determinetheelevationheaddifference

Theelevationheaddifferenceisthedifference(inft.)inelevationfromthelowwaterlevelinthepumptanktothedischargepoint.

Thisisusuallyapositivevalue,butforsystemswithadischargepointbelowthepump,itmaybeanegativevalue.Ifthedischargeisbelowthepump,theuseofananti-siphoningdeviceisnecessary.


53


Step23:

DeterminetheTotalDynamicHead(TDH)

Thetotaldynamichead(TDH)(inft.),whichisusedtosizeandselectthepump,isthesumofthefollowingheadlosses:

Squirtheight (Step6)

Lateralheadloss (Step13)

Manifoldheadloss (Step16)

Forcemainheadloss (Step19)

Miscellaneousheadloss (Step20)

Zonevalveheadloss (Step21)

Elevationheaddifference (Step22)

Step24:

Selecttheappropriatepumpsizingcriteria

ThepumpspecifiedandinstalledinthesystemmustbesizedbasedonthedesignflowrateandthecalculatedTDHforthesystem.

Ifchangestothedesignaremadeduringinstallation,theywilllikelychangethesystemcalculationsforflowand/orTDH.Therefore,thedesignershouldclearlydocumentthedesignbasisandallcalculations.

Thedesignflowrate(ingpm)determinedinStep14isusedforpumpselection.TheTDH(inft.)requiredforthepumpisdeterminedinStep23.

54


Step25:

Determinetheapplicabledosevolume

Thesystemdosevolumeistheamountofeffluentthatthepumpwilldeliverduringasinglecycleevent.Thisvolumewillincludethedoseappliedtotheabsorptionareaaswellasanyvolumerequiredtofillthepipenetwork.

Themaximumdosevolumeforanypumpeventshouldbenogreaterthan10%ofthedailydesignflow.Smallerdosevolumesarepreferred.Thiswillresultisabout5dosesperdayforthetypicalaveragedailyflow.AppendixBTableB-8:Voidvolumeforvariousdiameterpipesisusedtocalculatepipevolumesbasedonpipediameter.

Whentimed-dosingisused,itwouldbeappropriatetohavemorefrequentdosesappliedduringtheday.Smallerdoseswillprovidemoredosesduringa24-hourperiodandmayresultinbetterperformanceoftheonsitewastewatersystem,whichmayleadtoalongerdesignlife.Therefore,thesystemshouldbeabletoprovidedosesthataresmallenoughtoprovidemultipledosingevents,spreadevenlyovertime,duringtheday.Formostsystems,thiswillbeadosevolumeof5%orlessforeachdosingevent.

Oncethetargeteddosevolumehasbeenchosen,theactualpumpingdosevolumemustbedetermined.Forsystemsinstalledincoldweatherconditions,withdrainbackorifices,theforcemainpipingandmanifoldnetworkwillneedtobefilledduringeachpumpcycle.Thevolumeofthesepipesshouldbeaddedtothedosevolume.PipevolumesareprovidedinAppendixBTableB-8:Voidvolumeforvariousdiameterpipes.

Forademand-controlledsystem,thefloatsaresetinthedosetankwiththeappropriatespacingbetweenthepumponpositionandthepumpoffpositiontodelivertheselecteddosevolume.

Fortimer-controlledsystems,thepumprateneedstobedeterminedbymeansofadrawdowntestormeter.Usingthepumpflowrateoftheinstalledsystem,thetimer“on”settingcanbedeterminedtodelivertheselecteddosevolumeforeachpumpingevent.


55


Step26:

Developasystemperformancecurve

Thesystemperformancecurvepredictshowthedistributionsystemwillperformundervariousflowratesandheads.

Theflowrateisaresultofthetotalheadthatthepumpworksagainst.Astheheadincreases,theflowratedecreases.Theflowratedeterminesthenetworkpressureandthustherelativeuniformityofdischargethroughoutthedistributionnetwork.

Thebestwaytoselectthepumpistoevaluatethesystemperformancecurvevs.thepumpperformancecurve.Wherethetwocurvescrossiswherethesystemwilloperaterelativetoflowrateandhead.

SystemevaluationinvolvescalculationsthatareexplainedstepbystepinAppendixA.Pumpperformancecurvesaresuppliedbypumpmanufacturers.

Plotthesystemheadcurveandpumpcurvetogethertodetermine:

1. Wherethepumpwilloperateonitscurve

2. Whatchangeswilloccurifthesystemheadcurveorthepumpperformancecurvechanges

Table18:Designsteps

Figure10:Systemandpumpperformancecurves


57

4.0 PressureDistributionDesignSubmittalRequirements

Suggestedinformationthatshouldbeprovidedinthesystemdesignplansincludes:

• Allpumpcalculationandresultsnecessarytodocumentthatthesystemisdesignedandsizedfortheappropriateflowsmustsubmitted.Informationonhowthedailyflowratewasestimatedshouldalsobeincluded.

• Thedesignshouldclearlyshowtheplacementoftheequipmenttobeinstalled.

• Componentsthatarecriticaltotheoperationofthesystem,suchaspumps,floats,controlpanels,effluentfilters,etc.,shouldbeclearlyspecifiedinthedesigntoensurethattheproperequipmentisinstalled.Adequateinformationshouldbeprovidedforthecontractortounderstandwhatistobeinstalledaswellastheinspectortoverify.

• Pumpingsystemsrequireaccessfromthefinishedgroundsurface.Knowledgeofappropriateequipmentneededforasafeinstallationthatprotectstheenvironmentandpublichealthmaybeunfamiliartothecontractorandtheinspector.Thedesignershouldincludedetailsanddrawingsinthedesignthataddresshowtheaccesstogroundsurfaceistobeachievedinasafemannertopreventunauthorizedaccess,especiallybychildren.

• Electricalrequirementsfortheinstalledequipmentshouldalsobespecifiedinthedesign.

• Manyofthesiteswherepressurizedsystemsoralternativesystemswillbeusedhavesiteconditionsthatlimittheinstallationofaconventionalsystem.Inmanycasestheremayonlybeoneacceptablesolutionforthesite;thereforethedesignplansmustbefollowed.Detailsregardingthelocationofthesystemshouldbecleartoallwhoreviewtheplans.

• Whenpumpingassembliesareinstalledinatank,thedimensionsofthetankwilldictatethelocationofthepumpand/orthefloats.Therefore,thedesignermustprovidethesizeanddimensionsofthepumpchamber,basin,orvault,designatespecificcomponentstobeused,andspecifythespacingsthataretobeusedforpumpandfloatplacement.Ifalternativecomponentsareproposedforuse,thedesignerandregulatoryauthoritymustbeconsultedtoensureproperinstallationoftheequipment.Thisrequirementshouldbeclearlynotedontheplans.

• Ataminimum,thepumpspecificationsshouldalsoincludethefollowinginformation:

– Pumpmanufacturer– Modelnumber– Horsepower– Voltageandphase– Amperage(runamps,startingamps,fullloadamps)– Capacity:NumberofgpmatthespecifiedfeetofTDH– Pumpcurvewithsystemcurve

58

• Ifalternativeequipmentisused,documentationoftheapprovedchange,includingwhoapprovedthechange,mustbeprovidedtothepropertyownerandincludedintherecordfileattheregulatoryoffice.

• Detailsofsystemdesignthatwerecalculatedusingthedesignspreadsheet(ordesignsoftware)shouldalsobeprovided,including:

– Septictanksize,locationandoutletinvertelevation– Pumpelevationandlocation– Forcemainlength,location,highestelevation,anddiameter– Allvalves,othercomponentsandfittingsinthesystem– Manifolddiameter,location,length,andorientation– Lateraldiameter,location,length,orientation,andelevations– Orificediameter,spacing,andorientation– Dosevolumeandfrequency– Locationanddetailofaccessportsonthelaterals.

• Auser'smanualforthepressuredistributionsystemshouldbeprovidedtothehomeowner/systemuserandthelocalhealthdepartment.Thisdocumentmaybedevelopedinconjunctionwiththeinstallerandsubmittedwiththeas-builtinformation,butthedesignerisresponsibleforpreparationofthemanual.Thecontentsoftheuser’smanualshouldinclude,ataminimum:

– Diagramsofthesystemcomponents.– Explanationofgeneralsystemfunction,operationalexpectations,owner

responsibilities,etc.– Specificationsofallelectricalandmechanicalcomponentsinstalled

(occasionallycomponentsotherthanthosespecifiedontheplansareused).– Namesandtelephonenumbersofthesystemdesigner,localhealth

department,componentmanufacturers,supplier/installer,and/orthemanagemententityorserviceprovidertobecontactedintheeventofafailure.

– Informationontheperiodicmaintenancerequirementsofthevariouscomponentsoftheonsitesystem.

– Informationontroubleshootingcommonoperationalproblemsthatmightoccur.Thisinformationshouldbeasdetailedandcompleteasneededtoassistthesystemownerorusertomakeaccuratedecisionsaboutwhenandhowtoattemptcorrectionsofoperationalproblemsandwhentocallforprofessionalassistance.


59

5.0 TestingandInspectionofPressureDistributionSystemafterInstallation

Testingandinspectionofapressuredistributionsystemshouldbeconductedtoverifythatdistributionisuniformwiththerequiredminimumresidualpressure,thatthesystemisdosedatthepropervolumeandfrequency,andthatthealarmsarefunctioningproperly.

Ifproblemsareencounteredduringtesting,theinstallershouldnotifythedesignerorengineer.

Specifically,thefollowingcomponentsofapressuredistributionsystemshouldbeinspectedandverified,priortobackfill,bytheregulatoryauthority,thecontractorand/orthedesigner.

Inpreparationforinspection,thepumpchamber,vault,orbasinshouldbefilledwithwater.

• Watertighttanksmustbeinspectedandverifiedaswatertightafterinstallation,asthisisacriticalcomponentinpressurizedsystems.Ifthetankallowsinfiltrationofwaterintothetank,excessivequantitiesofgroundwaterwillbepumpedontothereceiverinfiltrativesurfaceandwilloverloadthesystem,leadingtoanearlyfailure.Infiltrationcanalsocausehighwaterusealarms.Theseproblemscanbeexacerbatedduringwetperiodsofseasonallyhighgroundwater,snowmelt,orheavyrainfall.Ex-filtrationofeffluentoutofthetankcancauselowwateralarmsunderlowornoflowconditions.

• Thepumpmustdeliverthecorrectdosetotheabsorptionarea.Fordemand-dosesystems,verificationthat"dry"floatsettingswillsendthecorrectdosetothedispersalareawhenfloatsareinwatermustbemade.Minoradjustmentsoffloatplacementmayberequired.Thedrawdownperdosemeasurementsshouldberecorded.

• Allfloatsmustbeinspectedforproperoperation.Commoninstallationerrorsincludeincorrectwiringoffloats.Careshouldbetakentoensurethatwhenthefloatismovedfromtheupordownpositionthatthecorrectsignaloccursatthecontrolpanel.

• Thefloatsshouldturnonandoffatthecorrectwaterelevationsforthehighwateralarm,“on”level,“off”level,and“redundantoff”levelasidentifiedonthedesignplan.Forsimplicityandaccuracy,theseadjustmentsshouldbemadewiththefloattreeoutofthewater(“dry”floatsettings).

• Theaudibleandvisualalarmfunctionsofthecontrolpanelshouldbeconfirmed.

• Insomeregulatoryjurisdictions,asystemmustbedesignedsuchthatthehighwateralarmdoesnotturnthepumpon.Ifthehighwateralarmturnsthepumpon,thesystemwillnotbeapproved.Highwaterlevelsthatsetoffalarmsshouldbeinvestigatedastothecauseofthecondition.Ifthecauseisduetotemporaryperiodsofhighwateruse,theexcesswaterwillbepumpedoutthroughthe

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system.Ifthehighwaterlevelsareduetoon-goingconditions,suchasleakyfixturesortoilets,thoseproblemsshouldbecorrected.

• Theinstalledpipingshouldbepressurizedtoverifythatitdoesnotleakpriortobackfill.

• Drainbacksystemsrequirereverseslopebacktothedosetankinordertoensureproperdrainagebetweenpumpevents.Beddingaroundthepipemustbeadequatetopreventsaggingofpipes,whichmayretainwaterandfreezeduringlowornoflowconditions.Anydipinthepipingmustbeleveledpriortobackfill.

• Thesquirtheightmustmeetdesignspecifications.Theuniformityofsquirtheightalongthelengthofthelateralsshouldbeevaluated.Theactualsquirtheightsatbothendsofeachlateralatthetimeofinspectionshouldberecordedifpossible.Ifthesquirtheightvariesfrominlettooutletendofthelateral,theheightdifferencemustbeevaluatedtoensurethattheflowfromtheorificesiswithin10%fromthefirstorificetotheendorifice.

SquirtheightcanbemeasuredbyattachingaclearPVCstandpipetotheendofthelateral.TheinitialsquirtheightattimeofinstallationwillbeusedduringperiodicinspectionsoverthelifeofthesystembytheO&Mserviceprovider.Theresidualheadismeasuredfromthetopofthelateralpipetothetopofthewatercolumn.

• Allaccessrisers,includinglidsandlidboltsmustbeinspectedtoverifythattheyaresecureandsafe.

• Allinstalledvalvesshouldbeinspectedandverifiedtobeworkingasdesigned.

• Otherstandardinspectionrequirementsmustalsobeconfirmed,suchascomponentsizing,locations,elevations,etc.

Timed-dosetesting

Fortimed-dosesystems,thetimerruntimesprovidedbydesignersmustbefield-testedtoseeiftheseruntimeswillsendafulldosetothereceivingcomponent.Thisdeterminationcanbeaccomplishedbyrunningthesysteminmanualandmeasuringthetimeintervalrequiredforafulldosetobepumped.Theremustbesufficientwaterinthepumpchambertorunthesetests.

• Usingthetimerequiredtopumpafulldose,itmustbeverifiedthatwhenthesystemrunsautomatically,thatitrunsforthetimerequiredtosendtheproperdosetothereceivingcomponent.Timerscanbedifficulttoset,i.e.,settingatimerto2.2minutesmaynotensurearuntimeof2.2minutes.

• Thetimer“off“timeshouldbethesameasthatspecifiedintheplanorshouldbeabletodosethesystemthecorrectnumberoftimesperday.Forinstance,ifthereceivingcomponentistoreceive4dosesperday,the“off”timeshouldbeapproximately6hours.


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Post-inspectionfollow-up

Problemsencounteredduringaninspectionmustberesolvedbythecertifieddesignerandtheregulatoryauthority.

Wiringproblemsshouldbereferredtotheelectricianwhoinstalledtheelectricalcomponents.

Anyapprovedchangestothedesignsubmittaldocumentshouldberecorded.

Informationfromthefinalinspectionshouldberecordedinanas-builtconstructiondocument.Thisinformationshouldbeprovidedtotheregulatoryauthority,thesystemowner,andtotheoperationandmaintenance(O&M)serviceprovider.


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6.0 OperationandMaintenance(O&M)Criteria&Recommendations

Permitrequirements

MostofthepermittedsystemsthatutilizepressurizeddistributionrequireanoperatingpermitfromeithertheStateofUtahDivisionofWaterQualityorfromalocalhealthdepartment.

SpecificO&Mrequirementsforaparticularsystemshouldbeidentifiedduringthepermittingandapprovalprocess.

Maintenancerequirements

Thetypicalpressurizedsystemmustbemaintainedonaregularbasis.AlternativetreatmentsystemsusingpressurizeddistributionsystemsasdefinedinR317-4requireasemi-annualinspection.

Duringthesemi-annualinspection,maintenanceobservationsandactivitiesshouldbeloggedandreviewed.Oftensmallchangesinsystemperformance,ifobservedanddocumented,canbeusedtoinitiatepreventativemaintenancethatcanreduceoreliminatefutureproblemsandexpenses.

O&Mactivitiesmayincludethefollowing:

• Conductawalkthroughoftheareawherethesystemisinstalled.Lookforanyindicationofsurfacingeffluentandalsolookforchangestothesitefromthepreviousvisittoensurethatthesystemintegrityremainsintact.

• Checkalltanksandmeasureandrecordsludgeandscumlevels.

Pumptankswhennecessary.GuidelinesforwhentopumpatankarefoundinR317-4.

Checkforsignsofleakingintanksandrisers.Lidsofrisersmustbesecure.

• Checktheinletandoutletofthetanks,includingthebafflesortees,toensurethattheyarenotdamaged,broken,clogged,ormissing.

• Removeandcleantheeffluentfilterifnecessary.Re-installafterinspectionandcleaning.

• Inspectandverifyvalvestoensurethattheyareworkingasdesigned.

• Inspectfloatsforproperoperation.Floatfailureisacommoncauseofsystemfailures.Movementofthefloatsshouldnotberestricted,andthefloatsshouldbepositionedcorrectlyandprovidepositiveinstrumentationsignals.

• Measurepumpruntimepercycleanddrawdown.Comparethesevalueswiththoserecordedintheconstructionrecordandpreviousinspectionrecords.Ifthevaluesaredifferent,evaluatethesystemforimproperlysettimercontrolsorfloatsettings,cloggedlaterals,orpluggedorifices.

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• Checkandverifyconnectionsinspliceorjunctionboxestoensurethatwhenthefloatismovedfromtheupordownposition,thecorrectsignaloccursatthecontrolpanel.Testalarmsforproperfunctioningathighandlowliquidlevels.

• Checkandverifythecontrolpanelfunctionsaccordingtotheapproveddesign.

• Measureandrecordsquirtheightandcomparetopreviousrecordingsandinitialmeasurements.Increasingsquirtheightsindicatetheneedtoflushorcleanalateralpipe.Lowersquirtheightsusuallyindicateaproblemwiththepipenetworkbutmayalsobearesultofaproblemwiththepumpsystem.

SquirtheightcanbemeasurebyattachingaclearPVCstandpipetotheendofthelateral.Thetrueresidualheadismeasuredfromthetopofthelateralpipetothetopofthewatercolumn.

• Confirmthattheaudibleandvisualalarmfunctionsofthecontrolpanelareoperational.

Allfindingsandrepairsmadeduringthesemi-annualO&MinspectionsshouldberecordedandfiledforeasyaccessandreportssenttothelocalhealthdepartmentortheUtahDivisionofWaterQuality,asrequired.


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AppendixA:PressurizedDistributionDesignWorksheet

Pleaseentertheresultsofyourcalculationsforeachstep.

AbsorptionAreaDesign

AbsorptionAreaDesignNotes: Step:

Forresidentialsystems,determinethenumberofbedroomsfordesign.Fornon-residentialsystems,determinethenumberofgallonsperdayusingguidancefromR317-4.

Forabsorptionsystemsandmoundsystems,use150gallonsperdayperbedroom.

Forpackedbedsystems,use:

Aminimumof300gallonsperdayfortwobedrooms100gallonsperdayforeachadditionalbedroom.

1. Dailyflowrate

Numberofbedrooms: ______

Totalgallonsperday: ______

Forpressurizedtrenchesforresidentialandnon-residentialsystems,selecttheloadingrateusingguidancefromR317-4

Formoundsystems,use1.0gal/sq.ft./day

Forpackedbedsystems,selectfrom:

Intermittentsandfilter:Sandmedia=1.0gal/sq.ft./day;Sandfill=1.2gal./sq.ft./day

Recirculatingsandfilter:5.0gal/sq.ft./day

Recirculatinggravelfilter:15.0gal/sq.ft./day

Textilefilter:30.0gal/sq.ft./day

Peatfilter:5.0gal/sq.ft./day

Syntheticpolystyrenemediafilter:21gal/sq.ft./day

2. Maximumloadingrate______gal/sq.ft./day

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AbsorptionAreaDesignNotes: Step:

Forpressurizedtrenches,useabsorptionareasizingtablesfromR317-4

Forpressurizedtrenchesafterpackedbedsystems,useabsorptionareasizingtablesfromR317-4andallowablereductionfactors.

Formoundsystems,usevaluesofA(absorptionareawidth)andB(absorptionarealength)fromMoundDesignWorksheet

Forpackedbedsystems,use:

Dailyflowrate(fromStep1)/maximumloadingrate(fromStep2)=requiredtreatmentabsorptionarea.

3. Requiredabsorptiontreatmentarea______sq.ft.

Forpressurizedtrenchesandpackedbedsystems,use:

Lengthxwidth=absorptiontreatmentarea

Thelayoutwillbedependentonthecharacteristicsofthespecificsite.

Formoundsystems,usethevaluesofAandBfromtheMoundDesignWorksheet(availablefromtheUtahOn-SiteWastewaterTreatmentTrainingProgram).

4. Sketchaproposedabsorptiontreatmentareaforthesystembeingdesigned,usingtherequiredabsorptionarea

PressureNetworkDesign

PressureNetworkDesignNotes: Step:

1/8inch–canbeusedonallalternativesystems&pressurizedtrenches

5/32inch–typicallyusedinpressurizedtrenches

3/16inch–canbeusedinmoundsorpressurizedtrenches

1/4inch–canbeusedinmounds(butgenerallynotrecommendedforuseinpressurizedsystemdesign).

5. Orificediameter

______inch


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Selectthesquirtheightusingorificediameter(Step5)

1/8inch: 3-5ft

5/32inch: 2-4ft

3/16inch: 2-3.5ft

1/4inch: 2-2.5ft

6. Minimumsquirtheight

______ft.

Determinetheorificeflowrate(SeeAppendixBTableB-5:Orificeflowrates)usingtheorificediameter(Step5)

Examplesoforificeflowratesinclude:

1/8inchwith5ftsquirt=0.41gpm

5/32inchwith3.5ftsquirt=0.54gpm

3/16inchwith3.5squirt=0.78gpm

1/4inchwith2.5ftsquirt=1.17gpm

7. Orificeflowrateingallonsperminute(GPM)______

Selecttheorificespacing:

1orifice/6ft2–mounds

1orifice/4ft2-intermittentsandfilter

1orifice/4ft2orless-recirculatingsandfilter,recirculatinggravelfilter,textilefilter

Forpressurizedtrenches,orificesaretypicallyplacedevery2to4feetalongeachpressurizedlateral.

8. Orificespacing______ft.

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Basedonorificespacingandshapeofdistributionarea(fromStep4sketch),determinenumberandlengthoflaterals:

Numberoflateralsisalllateralsinthesystem

Numberoflateralsdosedbypumpisthenumberoflateralsdosedwhenthepumpruns.Itisthesameasabovewhenzonesarenotused.Itisthenumberoflateralswithinthezonewhenzonesareused.ThisnumberisusedfordeterminingthedesignflowrateofthepumpinStep14

Forendfeed:laterallength=

absorptionlengthminus0.5to1foot

Forcenterfeed:laterallength=

absorptionlengthdividedby2minus0.5to1foot

Lateralsshouldextendtowithin6inchesto1footoftheendoftheabsorptionarea.

Thedistancefromthelateralstotheedgeoftheinfiltrativeareashouldbe6inchesto1footforbedareasand1footto1.5feetfortrenches.

9. Numberandlengthoflaterals

Numberoflaterals:

______

Numberoflateralsdosedbypump

______

Lengthoflaterals

______ft.

AddthelateralstothesketchinStep4

FromStep8andStep9:

Numberoforifices=(laterallength/orificespacing)+1

Ifthecalculationresultsinafraction,dropthedecimalthenaddtheadditionalorifice.

10. Numberoforificesineachlateral

______

FromStep7andStep10:

(Orificeflowrate)x(Numberoforifices)

11. Lateralflowrate

______GPM


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Sizethelateraldiametertoensureflowwithinthelateraliswithin10%.

UseorificediameterfromStep5.

UseGraphsB1throughB8inAppendixBtodetermineminimumlateraldiameters:

UseGraphB-1orB-2for1/8inchorifice




12. Lateralsizing______in.

DeterminelateralheadlossusingMethod1or2:

Method1:use1/3ofthesquirtheightfromStep6:

(squirtheight)x(0.33)

Method2:calculatetheheadlossbasedonsolidpipe1/3thelengthoftheperforatedlateralfromStep9,usingthelateralflowratefromStep11andthediameterofthelateralfromStep12.SeeAppendixBTableB-6,FrictionalHeadLossper100feetofSolidPipe.

13. Lateralheadloss______ft.

Calculateflowratefromalllateralsdosedatonetime.Thiswillbethetotalflowrateforalllateralsoralllateralswithinazone:

(No.oflateralsfromStep9)x(LateralflowratefromStep11)=DesignFlowRate.

14. Designflowrate______GPM

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DeterminethesizeofthemanifoldusingMethod1or2:

Method1:usethesamesizepipeusedfortheforcemaininStep18.

Method2:calculatetheheadlosswithinthemanifoldusingvarioussizesofpipeandusing1/2ofthetotaldesignflowfromStep14.

UseAppendixBTableB-6:FrictionalHeadLossper100feetofSolidPipe.

Selectan“acceptable”headloss-usuallyselectthesmallestpossiblepipe.

Manifoldheadlossshouldbe<40%oftotaldynamichead(TDH)fromStep23.

15. Manifoldsizing______in.


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DeterminemanifoldheadlossusingAppendixBTableB-6:FrictionalHeadLossper100feetofSolidPipe

16. Manifoldheadloss______ft.

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Lengthofpipefromthepumpdischargetothebeginningofthemanifold(site-specific).

17. Forcemainlength______ft.


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UseAppendixBTableB-6:FrictionalHeadLossper100feetofSolidPipetodeterminethepipediameter.

Pickapipediameterwithanacceptablerangeofheadloss.

Maybeaniterativeprocess.

18. Forcemaindiameter______in.

DeterminetheforcemainheadlossfromAppendixBTableB-6:FrictionalHeadLossper100feetofSolidPipeusingtheforcemainpipesizediameterfromStep18.

19. Headlossinforcemain______ft.

Estimateadditionalheadlossforfittings,valves,etc.UseMethod1or2

Method1:add50%oftheforcemainheadlossfromStep19toaccountforfittings,valves,etc.

Method2:Determinethe“equivalent”pipelengthsforfittings,valves,etc.anddeterminetheheadlossfromAppendixBTableB-7:Frictionallossesthroughplasticfittings.

20. Miscellaneousheadloss______ft.

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Determinetheheadlossthroughautomaticdistributingvalve.Thisinformationisusuallysuppliedbythemanufacturer.

21. Headlossforsystemswithmultiplezones(ifused)______ft.

Theverticaldistance(elevationdifference)fromthewaterlevelinthepumptanktothewaterlevelatthedischargepoint(site-specific).

22. Elevationheaddifference______ft.

TodeterminetheTDH,addtogether:

SquirtHeight(Step6) __________

LateralHeadLoss(Step13) __________

ManifoldHeadLoss(Step16) __________

ForceMainHeadLoss(Step19) __________

MiscellaneousHeadLoss(Step20) __________

ZoneValveHeadLoss(Step21) __________

Elevationheaddifference(Step22) __________

Resultinfeet=TDH __________

23. TotalDynamicHead(TDH)______ft.

DesignFlowRate(Step14) gpm__________

TotalDynamicHead(Step23) ft.__________

24. PumpSelection

USEPUMPCURVESTOSELECTTHECORRECTPUMP


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Thesystemdosevolumeshouldnotexceed10%ofthedailydesignflow.Smallerdosevolumesarepreferred.

Forsystemsthatdrainbacktothepumptankaftereachcycle,thevolumeoftheforcemainshouldbeaddedtothedosevolume.

PipevolumesarecalculatedusingAppendixBTableB-8:Voidvolumeforvariousdiameterpipes.

Totaldosevolumeisthesumofthedosevolumeandpipevolume.

25.SystemDoseVolume

______gal

PipeVolume______gal.

TotalDoseVolume

______gal

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Calculateasystemperformancecurvebycompletingtheworksheetonthefollowingpage:

a) InColumn1RowC,entertheDesignFlowRatefromStep14.ThenselecttwoflowratesabovetheDesignFlowRateandtwobelowandenterinrowsA,B,DandE.Column1shouldnowbecompleted.

b) InColumn2,calculatetheOrificeFlowbydividingtheTotalFlowRatefromColumn1bythenumberoforificesinthenetworkfromStep10.

c) InColumn3,entertheElevationHeadDifferencefromStep22.

d) InColumn4,useTableB-6:Frictionalheadlossper100feetofsolidpipetocalculatetheForceMainHeadLoss.

e) InColumn5,calculatetheNetworkHeadusing:H=1.3(Q/(11.79d2))2Hisforheadinft.Qisfororificeflowratefromcolumn2disorificediameterininchesfromStep5The1.3isanadjustmentfactorforfrictionlossinlaterals.Example:Theequationfora3/16”orificeisH=1.3(Q/0.4145))2

f) InColumn6,calculatetheTotalHead.AddtheElevation,ForceMainandNetworkheads.

g) Todevelopthesystemperformancecurve,plottheTotalFlowfromColumn1vs.theTotalHeadfromColumn6.

h) Usingmanufacturers’PumpPerformanceCurves,selectonethatintersectstheSystemPerformanceCurveabovetheTotalSystemFlowRate.

Step26:SystemPerformanceCurveandPumpSelection


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SystemPerformanceCurveWorksheet

1.TotalFlow(gpm)

2.OrificeFlow

(gpm)

3.ElevationHead

Difference(ft)

4.ForceMainHeadLoss

(ft)

5.NetworkHead(ft)

6.TotalHead

(ft)

A

B

C

D

E

DesignFlowRatefromStep14inRowC.SelecthigherandlowerratesinrowsA,B,D,E

DividetheTotalFlowRatefromColumn1bythenumberoforificesinthenetworkfromStep10

ElevationHeadDifferencefromStep22

UseTableB-6:Frictionalheadlossper100feetofsolidpipe

SeeStep26e)

AddtheElevation,ForceMainandNetworkheads


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AppendixB


81


83


85


87

OrificeFlowRatesinGallonsPerMinute(GPM

PressureinFeet

OrificeDiameter1/8” 5/32” 3/16” 1/4”

2.0 0.26 0.41 0.59 1.042.5 0.29 0.46 0.66 1.173.0 0.32 0.50 0.72 1.283.5 0.34 0.54 0.78 1.384.0 0.37 0.58 0.83 1.474.5 0.39 0.61 0.88 1.565.0 0.41 0.64 0.93 1.655.5 0.43 0.68 0.97 1.736.0 0.45 0.71 1.02 1.806.5 0.47 0.73 1.06 1.887.0 0.49 0.76 1.10 1.957.5 0.50 0.79 1.14 2.028.0 0.52 0.81 1.17 2.088.5 0.54 0.84 1.21 2.159.0 0.55 0.86 1.24 2.219.5 0.57 0.89 1.28 2.2710.0 0.58 0.91 1.31 2.33

TableB-5:Orificeflowrates

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FrictionalHeadLossper100feetofSolidPipe

GallonsPerMinute

NominalPipeSize3/4” 1” 1¼” 1½” 2” 3” 4”

3 3.24 0.80 0.27 0.11 0.03 0.00 0.00

4 5.51 1.36 0.46 0.19 0.05 0.01 0.00

5 8.34 2.05 0.69 0.28 0.07 0.01 0.00

6 11.68 2.88 0.97 0.40 0.10 0.01 0.00

7 15.55 3.83 1.29 0.53 0.13 0.02 0.00

8 19.91 4.90 1.65 0.68 0.17 0.02 0.01

9 24.76 6.10 2.06 0.85 0.21 0.03 0.01

10 30.09 7.41 2.50 1.03 0.25 0.04 0.01

11 35.90 8.84 2.98 1.23 0.30 0.04 0.01

12 42.18 10.39 3.50 1.44 0.36 0.05 0.01

13 48.92 12.05 4.06 1.67 0.41 0.06 0.01

14 56.12 13.82 4.66 1.92 0.47 0.07 0.02

15 63.77 15.71 5.30 2.18 0.54 0.07 0.02

16 71.87 17.70 5.97 2.46 0.60 0.08 0.02

17 80.40 19.80 6.68 2.75 0.68 0.09 0.02

18 89.38 22.01 7.42 3.06 0.75 0.10 0.03

19 98.80 24.33 8.21 3.38 0.83 0.12 0.03

20 108.64 26.76 9.02 3.71 0.91 0.13 0.03

25 164.24 40.45 13.64 5.61 1.38 0.19 0.05

30 230.21 56.70 19.12 7.87 1.94 0.27 0.07

35 306.27 75.43 25.44 10.47 2.58 0.36 0.09

40 392.20 96.60 32.58 13.40 3.30 0.46 0.11

45 120.14 40.52 16.67 4.11 0.57 0.14

50 146.03 49.25 20.26 4.99 0.69 0.17

60 204.68 69.03 28.40 7.00 0.97 0.24

70 272.31 91.84 37.79 9.31 1.29 0.32

80 348.71 117.61 48.39 11.92 1.65 0.41

90 146.28 60.19 14.82 2.06 0.51

100 177.80 73.16 18.02 2.50 0.62

125 268.78 110.59 27.24 3.78 0.93

150 155.01 38.18 5.30 1.30

175 206.23 50.79 7.05 1.74

TableB-6:Frictionalheadlossper100feetofsolidpipeBasedonHazen-WilliamsequationhL=L*(Q/(0.285*C*d^2.63))^1.852whereC=~145,L=100,Q=GPMHeadlossintablemustbecorrectedforpipelength:

(headLossfromtable)x(pipelength/100)=headlossinpipe


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FrictionalLossesthroughPlasticFittingsintermsofEquivalentLengthofSolidPipe

NominalPipeDiameterTypeofFitting 1/2" 3/4" 1" 1¼” 1½” 2" 3" 4"90oSTDElbow 2 2 3 4 4 6 8 12

45oElbow 1 1 2 2 2 3 4 5

STDTee 4 5 6 8 9 12 16 22CheckValve 4 6 7 9 11 14 19 25

QuickDisconnect 1 1 1 1 1 1 2 3AngleValve 8 12 15 19 22 28 40 55GlobeValve 15 22 27 35 45 60 80 110

GateValve-Open 1 1 1 1 1 1 2 31/4Closed 2 3 4 5 6 7 10 141/2Closed 10 14 17 22 25 35 50 703/4Closed 40 55 70 90 105 140 200 300

TableB-7:Frictionallossesthroughplasticfittings

PipeVolumes

NominalPipeDiameter Volume(gal./LF)1/2" 0.0103/4" 0.0231" 0.041

1-1/4" 0.0641-1/2" 0.092

2" 0.1633" 0.3674" 0.652

TableB-8:Voidvolumeforvariousdiameterpipes

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