practical design notes

8/12/2019 Practical Design Notes

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221 82GR o

GRAVITY FLOWWater Systems

P R A C T I C A L D E S I G N N O T E SF O R

S I M P L E R U R A L W A T E R S Y S T E M S

LA S C O T T F A I I A

S a n i t a r y E n g i n e e r

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GRAVITY FLOWa t e r S v s t c

P R A C T I C A L D E S I G N N O T E Sw F O R

S I M P L E R U R A L W A T E R S Y S T E M S

k O 3 H M

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A - H C O T T F A X X AS a n i t a r y E n g i n e e r

C A R E I N D O N E S I A

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GRAVITY FLOW WATER SYSTEMSPRACTICAL DESIGN NOTES FOR SIMPLE RURAL WATER SYSTEMS

CONTENTS PAGEC

1 Introduction2 . T heWater Source3. General System Designand

Design Parametersi^ *t.Pipeline Design

, 5 SummaryofSug gestedDesign Guidelines 19

L

13

611

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-^

25

1 018

Appendices

A. General ExplanationofFlowand Head LossesinClosed Fip es A1 - A't

B* Head Loss Calculations B1 - HC. Construction Notes C1 - C9D. StepsinSurveyandDesign piE. Sample Designfo rDesa Gembira E1 - E8F. Glossary v\ _ i?k

Q ConTersion Fao ctor o and Q 1Population Growth F a c t o r s

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1. INTRODUCTION1.1. These deaign notes primarily coyer simple gravity flow water systems.

This is often the only feasible alternative for many rural areas atthe present time and in many countries a major portion of the fundsavailable for water systems are allocated to gravity flow systems.Howev er, field inspections of completed projects and the literatureindicate that there is a lack of capable design personnel and asubstantial number of systems do not function properly due to poordesi gn. Emphasis in the notes is placed on those aspects most neglected or misunderstood. Certain topics such as maintenance, community participation and health education are beyond the scope of thismanual but must be given due consideration in constructing any typeof water system,

1.2. These design notes present simple examples and explanations toillustrate some of the basic principles of gravity flow systems.Suggested guidelines * for design parameters are also presented.The theory of water system design is extensively covered in otherpublications. The emphasis here is placed on practical methodsthat have been tested in the field and have given acceptable results.However, it must be emphasized that there are no set or standardsolutions for the design of a water system. Attempts to implementwater supply programs using a limited number of standard designscan be expected to produce poor resu lts. Each community is uniqueand will require its own carefully prepared design by a personthoroughly familiar with local conditions.

1.3. The notes are based on several years experience in Indonesia andhave been used for training of field staff responsible for siteselection, design,and implementation. They are intended for useby persons responsible for planning, designing,and implementing,rural water systems. While a technical background or prior familiarity with water systems would obviously be useful it is intendedthat the material can be understood by persons without such a background. Since the guidelines are based on Indonesian conditionsthey should be applied with caution in other social, cultural andphysical setti ngs.

an asterisk denotes terms contained in the glossary in AppendixF. Such terms are so marked the first time they appear in the text.


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- 2 -o1,4. The type of systems discussed are simple branched systems as in

the example in Appendix E. Several dozen systems have been constructed using the design guidelines and they generally serve populations of 1,000 to5,000and are 2 to 8 kilometers in length. Thelargest system constructed using the suggested guidelines contained59 distribution reservoirs of 6 m3 capacity, seven break pressure 'tanks,and over 20 kilometers of distribution pipe. The flow inthe system is approximately 15 1/s and this serves a 1982 populationof approximately 12,000.


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2.THE WATER SOURCE2.1. General Considerations

2.1. 1. The water source should be free of fecal contamination andmust supply continously a minimum amount of water to the system (purity andreliability). Roth of these aspects aredifficult to measure with accuracy. Quality and quantity willfluctuate around some mean value under natural conditions andand the variations from the mean tend to increase as the natural ecological balance is disturbed. A major change suchas transformation from forest to agricultu re, can be expectedto significantly affect quantity and quality. Decreasedyields and the total drying up of the springs are not uncommon.

2.1.2.The source also must be protectable and containable . In muddyareas and soft soil it i6 sometimes impossible to collect andprotect the water. Areas of seepage rather than true springsare also difficult to deal with. Limestone areas must bethoroughly investigated because the spring could easily shiftposition altogether and the possibility of contamination isgreater.

2.1.3 Another key consideration is the source's availability for usein the system. It is frequently not possible to use waterpreviously used for irrigation, already allocated to otherplanned schemes or from sacred areas.

2.2.Estimation O f Quantity2.2.1. Accurate measurement of quantity would require frequent

monitoring over a period of several years and should preferably include a drier than average year. However, thisinformation is generally not obtainable and an estimationmust be made from point measurement s*. As many point measure ments as possible should be taken and they should be duringthe driest part of the year. Experience and judgementare critical. Note should be taken of the condition of thecatchment area, vegetation, land use etc. Comments of longtime local residents regarding reliability and changeover time are also useful. These however, must be weighedcarefully because people always tend to overestimate flowsduring dry periods and will sometimes falsely report thata source never drys up for fear of losing the project. It iabest to be conservative when estimating the minimum flow ofwater from spring.


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o Eatima-1ion Of Quality

231.Quality generally fluctuates much less than quantity but itwould also require monitoring over a long period to establishan accurate estimation. Point meaaurments should includeperiods of both high and low flows. In general, the greaterthe fluctuations the greater the amount of data that mustbe collected. The main considerations in assessing qualityre bacterial quality, consumer acceptability and chemicalquality.

2.32.Measurement of bacterial quality through teating for specificdisease causing agents is not practicable. Instead an indicator organism is used to assess the likelihood that the wateria contaminated by harmful pathogens. The most suitable indicator organism at present is fecal colifora* as determinedby the membrane filter technique*. The majority of fecalcoliform organisms are hot harmful to man but their associationwith fecal matter indicates that organisms dangerous to healthmay be present. However, the link between presence of fecalcoliform and contamination by fecal matter ia not yet firmlyestablished for tropical areas and further research is needed.The establishment of guidelines for bacterial quality is complicated by several other factors. Firstly, most sources underconsideration Qre unprotected and the simple act of cleaningup the area and protecting the source may often result indramatic improvements in quality. However, for politicaland social reasons, it is often imposaible to carry out suchimprovements without making a commitment to complete the watersystem regardless of changes in quality.Secondly, a rigid standard* may result in the rejection of asource which is superior in quality to existing sources . Thereplacement of a source containing several hundred thousandfecals per 100 ml by one with only 100 fecals per 100 ml canresult in dramatic improvements in health. Thirdly, there issufficient evidence to suggest that improving the quantity of water available without improving the quality will still resultin significant health benefits.

2.3.1*. In view of the above, only the most tentative bacterial qualityguidelines can be proposed. Each situation must be judged

on its merits. The obvious goal is no fecal coliforms present in any sample taken from the proposed source. If somecontamination exists then it is best if the average of allsamples is less than 50 fecals/100 ml and if no single sample


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exceeds 100 fecals/100 n>l For levels greater than these itis best to provide some form of treatment to improve qualityif the source is to be used.

2.3.>.All water sources should also be monitored several times ayear after source improvement and pipe installation. This ieuseful to document changes brought about by the improvementsand to guard against contamination.

2.3.O. Consumer acceptability of the water is of prime importance.The best designed system in the world will be useless if theconsumers do not accept and use the water. A simple visualinspection and sample testing of water along with a surveyof the intended users will usually suffice to determine acceptability. It is very importnnt to avoid excess iron in the

^ water that will turn tea or rice black. If a source has notpreviously been uBed for drinking then the water should b e boiledand tea made to check for any undesirable changes. Previouslyunusea sources are sometimes also objectionable for culturalreasons.

2.3.7. Extensive chemical testing is both costly and time consumingand is usually emitted if the water is acceptable to theconsum er. However, any unusual circumstances should be notedand guarded aga inst. For example, the presence of excess carbon dioxide may not be noticed by consumers but it would rapidly corrode steel piping.


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. GENERAL SYSTEM DESIGN AND DESIGN PARAMETERS3.1. Type Of Service

3.1.1. The level of service provided in rural Indonesia is generallydistribution at public taps for all types of domestic wateruse i.e. drinking, bathing, laundry,and toilet, ^roperlydesigned and maintained toilet fncilitier; nre not a health hazard.However, if there are serious doubtB that the people will notuse euch facilities properly or are totally unfamiliar with themthen it is better not to include theffl in the design. In aichcases a sample facility strategically located would be in order.

3.1.2. The distribution points and facilities should be freely access-able to all intended users, and should be located accordingto population density. Their design and placement shouldfacilitate and encourage water use thus maximizing projectbene fits. As general guidelines,no more than 10 to 20$ ofintended users should have to walk more than 100 meters toobtain water and the number of users per water faucet shouldbe between 30 to 100. For example,a small system serving1,000 people could have 6 distribution points (either stand-posts,reservoirs or public baths) each with four faucetsor approximately M persons per faucet. The lower range inthe design figure ahould be used for multiple purpose systemswhile the higher figures are acceptable for systems withrestricted use, e.g. drinking water only.

3.2.Water Usage - Design Figures3.2.1. Multiple use systems should penerally be designed for a per

capita use of 60 liters/day. If sufficient water is availablethe figure could be 80 or 100 liters per day. If water is extremely scarce and was to supplied for drinking purposes onlythe minimum acceptable figure would be 20 liters per personper day. These figures include an allowance for wastage.

3.3. Storage Capacity3.31. Storage of water is often necessary and will be influenced

by the nature of the water source and the design of the system.For example if the flow of the water source is just 1 1/s(86m3/day) and the average daily usage* is also 86 m3/day

. then a certain amount of storage must be provided.


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This is because t%o flov f water is constant throughoutthe 2k hoar period while the usage is not. Therefore, duringperiods of low usage, such as during the night tpart of the ..86 m3 will flow from the source and not be available for useunless it is stored. If the flow is high enough then thestorage i not necessary provided that the pipe is large enoughto provide sufficient water at the time of peak usage*. However, even with a sufficiently large source it is preferableto provide some storage at the point of use. This aspect isdiscussed in more detail in paragraph 332. Figures 1A to1D depict several possibilities for storage placement.

32.Fig 1A depicts the general schematic for placing storage atthe point of use. In most cases this is the preferred typeof design for the following reasons :a. The inflow to each reservoir can be regulated so that each

area receives a set allotment of water. If the people atthat reservoir tend to waste water then they can onlywaste their allotment but not that of othe rs. In a stand-pipe system with storage at the source,wastage would beuch greater if taps were left open .

b.The small reservoir acts to break pressure in the system,Thia means that faucets at the point of use have onlythe head of the reservoir itself on them and will lastfor a longer period of time. Seduced head at the pointof use also reduces wastage.

c. Storage at the point of use means that the main distribution pipe is in use at all times. It can therefore beof a smaller diameter and thus reduce oosts. (Influenceon total cost will depend on the flow of the sourcecompared to average daily usage as this will influencestorage costs).

d. It is generally easier to obtain community support andcultivate feelings of ownership and consequently improvemaintenance through the construction of small scatteredreservoirs as compared to one large distant reservoir andstandpipes. Additionally, the construction of small reservoirs allows each segment of the community to work atits own pace during construction and a lack of communityorganization will be less likely to impede the project.


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Figures 1A - 1Po STORAGE PLACEMENT

W4r*3tfy*C

F i g . 1A - Storage at the point of water usag e. This is the preferredschematic for placement of sto rage and requir es the smallestpipe diameter. Its advantages are outlined in paragraph 3*3.2 .

PUBLICsT/\ ND p tf>s

Fig. 1B - Storage far from source but still above distribu tionnetwor k, distribution from storage to public stn ndpip es. Thepipe line to the point of storage is the same as in F ig. 1Abut after the point of storage is the same as Fig . 1C nndID. This option should only be used when storage at thepoint of use is not possible.

Poaue.$r**tppiPes

Fig. 1C - No storage provided, distribution direct to public stand-pipes. This type of system requires a larger diameterpip eline. The cost i s sometimes less than that of thesystem in Fig. 1A but use of storage as in Fig. 1A ispreferable for reasons outlined in paragraph332.

. ***&

Fig. 1D - Storage provided at or near the Water source thon distributiondirect to public stan dpipes. The pipeline diameter is thesame as in Fig. 1C and this is the most expensive option.


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e. I n I n d o n e s i a t he u s e o f r e s e r v o i r s c a n e n c o u m g e w a t e r u s ea n d i n c r ea s e heal th ben efit s fr o m the s y s t em . W i th a fewa i c i t i o n a l w a l l s t he a r e a c a n p r o v i d e p r i v a c y f o r b a t h i n ga n d w a s h i n g t ha t i s o f t e n ex p l i c i t y r eq u e s t e d b y t he c o m m u n i t y . T he w a l l a o f t he r e s e r v o i r c a n a l s o b e u s e d f o rd i s p l a y i n g h ea l t h e d u c a t i o n m e s s a g e s ,

3 . 3 . 3 . T h e f o l l o w i n g e x a m p l e o f s t o r a g e c a l c u l a t i o n i s a p p l i c a b l ew he n s t o r a g e i s t o b e p r o v i d e d a t t he p o i n t o f u s e . ( s ee F i g .1 A ) . U n d e r n o r m a l c i r c u m s t a n c e s t h e n e c e s s a r y s t o r a g e i sd e t er m i n e d b y c o m p a r i n g t h e s u p p l y c u r v e w i t h t h e c o n s u m p t i o nc u r v e f o r t h e v i l l a g e . H o w e v e r , i n f o r m a t i o n o n t h e c o n s u m p t i o nc u r v e f o r I n d o n e s i a n v i l l a g e s i s n o t a v a i l a b l e a n d s o m e o t h er m e t h o di s n e c e s s a r y . B a s e d o n r e c e n t ex p e r i e n c e i n I n d o n e s i ai t i s r e c o m m e n d e d t h a t t he s t o r a g e c a p a c i t y b e f i x e d a t o n eh a l f t h e a v e r a g e d a i l y u s a g e a s d e t e r m i n e d b y t h e p o p u l a t i o nt o b e s e r v ed a n d p e r c a p i t a c o n s u m p t i o n . F o r e x a m p l e , a s y s t e ms u p p l y i n g 1 ,0 0 0 p e o p l e w i t h 6 0 l i t e r s / d a y w o u l d h a v e a n a v e r a g ed a i l y u s a g e o f 6 0 m 3 a n d w o u l d t h u s r e qu i r e 3 0 m 3 s t o r a g e c a p a c i t y . I f s t o r a g e w e r e p r o v i d e d a t t he p o i n t o f u s e a n d t he r ew e r e 6 d i s t r i b u t i o n p o i n t s , a s i n t h e e x a m p l e i n p a r a g r a p h3 . 1 . 2 . , i t c o u l d b e a c c o m p l i s h e d w i t h 6 d i s t r i b u t i o n r e s e r v o i r seac h 5 n>3 wi th fou r t a p s . T h i s s o l u t i o n w o u l d b e s u i t a b l e i ft he p o p u l a t i o n d i s t r i b u t i o n w e r e u n i f o r m . -J-f i t w e r e n o t u n i f o r m t he n t he r e s e r v o i r s w o u l d b e o f d i ffe r e n t s i z e a n d c o u l dh a v e d i ffe r e n t n u m b e r s o f f a u c e t s . F o r e x a m p l e, t he m a i n hea v i l yp o p u l a t e d a r e a c o u l d b p s e r v e d b y a 1 0 m 3 r e s e r v o i r w i t h 8 f a u c e t s . T h r ee a r e a s o f m e d i u m d e n s i t y w i t h r e s e r v o i r s o f 5 m 3a n d k f a u c e t s a n d t h r ee a r e a s o f l o w d e n s i t y w i t h r e s e r v o i r s o f2 ,5 ">3 a n d t w o fa u c e t s . T he i m p o r t a n t p o i n t i s t ha t t he t o t a ls t o r a g e c a p a c i t y a n d n u m b e r o f f a u c e t s R e m a i n s t h e s a m e ( o ra p p r o x i m a t e l y t h e s a m e ) b u t t h e i r p l a c e m e n t i s a c c o r d i n g t ofi el d c o n d i t i o n s . I n p r a c t i c e t h e n u m b e r s d o n o t d i v i d e s on e a t l y a n d s o m e a d j u s t m e n t s a r e n e c e s s a r y . F o r e x a m p l e , i f t hed e s i g n p o p u l a t i o n w e r e 961 t he n ee d ed s t o r a g e c a p a c i t y w o u l d b e2 8,8 m 3 . T h i s m a y b e r o u n d e d u p t o 3 0 m 3 s o t h a t a s t a n d a r ddes i g n fo r t a nks of 5 m 3 o r s u c h c o u l d b e u s ed . The u s e ofs t a n d a r d d e s i g n s fo r c e r t a i n s y s t e m c o m p o n e n t s c a n b e v er yc o n v e n i e n t a n d ec o n o m i c a l . T h e d e s i g n f i g u r e s a r e r o u g h a p p r o x i m a t i o n s o n l y , a n d c a n b e m o d i f i e d i f n e c e s s a r y

3 3 ^ T he r e a r e s i t u a t i o n s w he r e t he d i s t r i b u t i o n s y s t e m i s fe d f r o ma c e n t r a l s t o r a g e r e s e r v o i r a b o v e t h e v i l l a g e . ( S e e F i g s . 1 B a n d 1 P )


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This Js recommended primar ily when the populat ion dcn.-.ity is toogreat to all ow for placement of the storage reservoir s withinthe vill age. Because of their s maller size, standpi pescan. be more easily placed at strategic lo cat ions . The storagecapacity necessary for such a system will be determined by therat io o f '-he estimated min imu m fLow'of the sou rce to the avera gedaily flow* as determined by the design population and percapita us age. If the ratio is between one and two then storageshould be equal to o ne half of the average daily us ar e. If theratio is between two and three then the storage should be onequarter of average daily u sag e.. If the ratio is between threeand four then the storage should be one eighth of average dailyusage, ^f the ratio is greater than four then no sto rage isnecessary (See Fig. 1 C ) . If the ratio is less than one thenthe source doesn't have enough water to supply the design population with the projected per capita u se. The above figuresare rough approximati ons because detailed information on the demandcurve for water iB not generally available for rural areas inIndonesia.

335 For the example discussed in paragraph 3 33. (storage atthe point of use) the average daily usage was 60m3/day o r /0,7 1 /B and the required storage 30 m3 If the storage wereto be provided above the villa ge and the estimated minimum flowof the source were 1,0 1/s then .the required stor age wo uld be equalto half the average daily usage of 30 m 3 (ratio of source yieldto average daily flow between one and t w o ) . If the estimatedminimum flow o f the source were greater than 2,8 1/s (ratiogreater than four) then no storage would be necessary .Design of the distribution pipe for these cases is discussedin section *t.3.

336.The placement of storage facilities and distribut ion point srequires detailed field surveys and extensive contact withthe vil lagers. It can not be done from behind the draftingtable in the office.

l_an average daily flow of


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4 . PIP EL INE DESIGN4.1. General

'.I.I.Sizing of pipe depends primarily on three main factors :design flows*, length of pipe, and available head*. The firstis controlled by the designer while the second two are fixedfor a given village and sourc e. (The maximum design flow isusually limited to the estimated minimum flow of thesource).Calculation of the head loss* for the given flow and distancewill indicate which size pipe is necessary to ensure that thedesired flow will be obtained.

4.2. Design Flows For Storage In Reservoirs At the- Point Of Use4.2.1. The design flow for systems with storage at the point of use

is the same as the average daily flow. In cases where thereis sufficient water available this flow is determined accordingto the population served (plus expected increases for 10-15 years)and the per capita use . For example, a village has 1,000 inhabitants and village statistics indicate that population growthis 2%per year. The expected population in 15 years would thenbe 1,293 persons. l f the percapita use is estimated at 80 liters per day then the average daily flow is 103.4 n3 or 1.21/s (to convert m3/day to 1/s divide by 86.4). This is thedesign flow that will be used to calculate head losses from thesource to the first reservoir (first point of use) . Flows usedin calculating losses for subsequent sections of the pipeline will be reduced by the amount used at each distributionpoint, (See examples of head loss calculations in paragraph'.'t.5 and sample design in Appendix E.)

*-- 4.2.2. If no figure for population growth is available then 2%may be assumed. However, some villages in Indonesia have nearlyreached the saturation point and population growth is very lowdue to migration out of the villa ge. If this is the case thena figure of 1% or even zero should be used.

'3.Design Flows For Public fitandpost System4.3.1 w'hen no storage is provided in the village then there is no

water flowing in the pipe if the faucets are closed' arid thesystem not in use. In effect, the main distribution line isunderutilised and it i6 best to avoid this situation. Thedesign flows must be altered to account for this. If the taps-are fully open 23 %of the time (six hours per da y) then thedesign flow would be 4 times the average daily flow and thisis the recommended design guideline.^(A chart for calculating future populations is included in


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For the example in paragraph U.2.1.,if there were no storagein the village, then the design flow would be k x 1.2 1/sor ^.8 1/s. This obviously requires a larger diameter pipe andwill increase the cost of the distribution lin es. If the hypothetical case occured where water use were very concentratedin time (say all use between 6 am to 9 am) then a design of thistype would result in an actual per capita consumption lower thanthe design figure or in a number of users lower than the designfigure. Again the recommended design figure is based onrecent experience in Indonesia because adequate data on peakusage is not generally available for the area . The storagerequired in this situation will depend upon the flow of thesource as discussed in paragraph 3.3.^.

k.k. Calculation Of Head Losses''.I.General *

Calculation of head losses is based on empirical formulasderived from experimental data. To avoid the necessity of repeatedcalculations values are taken directly from charts, tables orslide calculators.^ the circular waterflow calculator developedby M.H. Hear & Co in England is recommended because it is sufficiently accurate and convenient to use, particularly for quickestimations in the field. Appendices A and B will assist inunderstanding head loss calculation* and should be reviewedby those readers without adequate background in fluid mechanics.


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cussed below.

4.^.3. Excesive HeadIn designing the pipeline it ie necessary to ensure thatthe pressure or head exerted on the pipeline and fittings doesnot exceed acceptable limits. This is accomplished by breakingthe continuity in the pipeline at appropriate points. A i m ?concrete brenk pr^raure tank divided into two compartmentsis normally used but in some cases a distribution reservoircan also serve this function. The maximum allowable head willdepend on the type of the pipe used and the fittings involved.The following are recommended guidelines :a. For steel pipe with no valves in the lower end Q maximum head

of 200 meters is allowable although 100 meters is more reasonable. A cutoff valve or means of diverting the water isnecessary at the top end to prevent flow in the pipe in caseof repairs. Because there are no means to stop the flowat the lower end the full static head*of 200 meter s will never be attained.

b.For steel pipe with v alves and other fittings it is bestto limit the maximum static head to 50 meter s. That is ifall valves are closed and water were stationary in the distribution pipe then the lowest point in each section shouldh*ve no more than 5 meters head.

c. For PVC the maximum allowable head is the manufacturersstandard for which the pipe is guaranteed. If this exceeds50 meters than care must be taken to avoid excessive pressureon any fittings in the line.

The above recommendations- should be viewed as approximate andcan be adjusted to conform with field cond itio ns. For example,if the total head were 65 meters it would not be absolutelynecessary to install a pressure release tank. Similarly theplacement of tanks on a long line would not be at exactly 50meters intervals of head but would depend upon the topographyand the land available for the tanks.

There are also instances where conformance to the recommendedguidelines is not possible or desirable. For example, if thepipeline descended steeply from the source 150 meter s down intoa valley and then rose 100 meter s on the other side to reach thevillage the washout valve at the low point crossing the valley


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CHECKING O F TK HYDRAULIC GRAD E LINE

Fifrure 2A

WATZ SOU9.C&

If the pipeline followed ground profile A then the choice of pipe with thegiven* HGL is ac ceptable. If the pipeline followed ground profile B thennegative pressure would exist in section C so the pipeline should bere-designed. See Fig . 2B

F i g u r e 2 B

w i r e * S O U R C E

The pipe diameters have been changed thus changing the HG L. Use of a largerdiameter p ipe near the source ensures that the HGL l ies entirely abovethe ground profile and is acceptable. Note that two pipe diameters arenow used between the source nnd r eservoir .' For each diameter the HGLhas a different slo pe. The slope is directly dependent on the head l ossso a smaller diameter pipe has a s teeper slop e.


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Thus the total hori lona for the 1,000 meter pipeline is 19 meterswhich closely matches the available head. The pipeline profileand HGL are plotted in Fig. 3.

Figure 3(Example 1 )

STATIC H C* J~ VC

S* J>/ST4/SCte

L-OSS

/

Example 2A water source is 1,000 meters from ^ampong Kering and it ie1,000 meters further to Kampung Kering Sekali. The differencein elevation between the source and Kering is 20 meters andbetween Kering and Kering "ekali it is also 20 meters. Thedesign flows are 2.0 l/s from the source to Bering and 0.51/s from Kering to Kering Sekali. What are suitable pipediameters ?

Calculated Head Losses for various pipes are as follows :

Llength

(meters)

1,0001,0001,0001,0001,0001,000

flow(1/s)

222o.50,50.5

pipediameter(inches)

32.5221.51.25

head loss(meters)

5113331126

Available head(meters)

20202 02 02020

A suitable selection of pipe would be 2,5 inch pipe for thefirst 1,000 meters and 1.25 inch pipe for the second 1,000meters. The total head loss is then 37 meters which closelymatches the total available head of ^0meters. Note thatthe second 1,000 meters has a head loss of 26 meters and anavailable head of only P.Ometers.


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This is allowable bW&nuoe the re i s excess hend ava ilabl e fromthe fi rs t 1,000 metprs of the pi pe line and the HGL i s alwaysabove the pipe li ne pr of i le. See Fig. *,

Figure 4(Example 2)

/500 2 000

Example 3A spring with aflowof 3 1/s is 500meters fromthebathingareaand themosqueis 1,000meters further. Aflowof 1 1/swillbeusedtoservethebathing areaand 2.0 1/s for themosque.The differenceinelevationis 10meters betweenthespringand bathing areaand 20meters betweenthebathing areaand themosque. What pipe sizesarerecommended?

Some calculated head lossesare asfollows:length(meters)5005005001,0001,0001,000500500

flow(1/s)33322222

pipe diameter(inches)32.5232.522,52

head loss(meters)5 123651133616

Available head(meters)101010202020-.

If2.5inches pipeisusedfor theentire1,500metersthetotalhead lossis 23meters whichisless thanthetotal availableheadof 30meters. Thusthedesired amountofwaterof mayflow. However,theHfiLasplottedinFig.5falls belowthe pi-peline profileandthisis notallowable.


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- 18 -Fipruro 5(Ex


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~ 19 -

5. SUMMARY OF SUGGESTED D"SIQN GUIDELINES5.1. Bacterial Quality : No fecal coliforms in any sample from the proposed

source. If this is not possible, then an average of less than 50fecals/100 ml for all samples with no single sample exceeding 100fecals/100 ml. For levels above this, simple treatment is advisablesuch as slow sand filtration.

5.2. Distance to Distribution Toint : No more than 20$ of intended usersto walk more than 100 meters to obtain water.

53 Number of Users per Water Faucet : Between 30 and 100, lower rangefor multiple use and upper range for drinking water use only.

Per Capita Usage : Multiple use systems at a minimum of 60 1/daywith up to 100 1/day preferred if sufficient water is available.Minimum of 20 1/day for supply of drinking water only.

Storage Capacity i For storage at the point of use one half of theaverage daily usage(ADU). For storage above the point of use(standpipes only) dependent upon the ratio of source yield to averagedaily flow. For a ratio between one and two then storage one halfof ADU? for a ratio between ?.and 3 then storage one eighth of ADU;for a ratio greater than four then no storage required.

56.Design Flows j If storage is at the point of use; use the averagedaily flow. xf storage is aboye the point of use (standpipes only)then use lour times the average daily flow.


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- A 1 -

A P P E N D I X A

GENERAL SXFLANATION FOR FLOW AND HEAD LOSSES IN CLOSED PIPES

1. Pressure Exerted by a Column of WaterA column of water exerts a force due to the weight of the water. Thepressure, or force per unit area, is dependent on the height of thecolumn of water. Therefore, head*or water pressure is usually expressedin terms of the equivalent height of water needed to exert that pressure.The pressure under static conditions is not dependent on pipe size.See Fig. A 1.

Figure A 1lf

7 7 k jfu

The pressure at the bottom of each column of wateris the same. It is 10 meters of head or 10 kg/ c2.The pressure midway in each column would be 5 metersof head or 5 kg/cm2.

2.Pressure in a Static SystemIn a system under static conditions the pressure at any point isdependent on the difference in height between the point in question

L , and the highest point in the system. If an opening is made in thepipe in any part of the system and a tube connected to it then thewater level will rise until it is the same as the highest point.See Fig. A 2 .

I sure A 2


24/51

- A 2 -

Fig. A2

The system is static nnd no flow occurs.The pressure or head at points B,CtF, and H isthe sameji.e. 10 meters'rhe rressure or head at pointR is 5 meters of the difference in height between points AfindE.If the pipeline were opened and a tnbe connected to itat point C or F then the water would rise 10 meters and be at the same level as points AtD,and Q.

(

3. Pressure in a Flowing SystemWhen water in the pipeline is flowing, then the pressure is no longerdependent solely on the height difference with respect to the highestpoint. There is a loss of pressure or head due to friction betweenthe water and the pipe. The pressure or head at any point is equalto the static head* (relative height difference) minus the head loss*due to friction. Because of the head lors the water will not riseto the same level as the highest point but only as high as the pressure

v

f\r ^ i ^ ^ ^ ^ L

z~-*r


25/51

- A 3 -o**. Factors Influencing Head Losses

The amount of head loss is influenced by the following factors :*" The length of pipe.

The longer the pipeline the greater the head loss. This loss isdirectly proportional to the length i.e. the head loss for 200 metersof pipe would be twice that for 100 meters under the same conditions.

b .The diameter of the pipe.The smaller the diameter of the pipeline then the greater the frictionwill be for the same flow of water. The differences are not proportional.

c. The flow of water in the pipe.The higher the flow of water in a given pipe the greater the head

I loss due to friction. Friction increases as the square of the ve locity.

d. The pipe material.The smoother the inner surface of the pipe the lower the head loss.Thus .since PVC pip* is smoother than steel or cast iron it h as alower head loss for identical conditions.

e.The number of fittings or bends in the pipeline.A straight pipeline would have a lower head loss than one of the samelength with fittings or bends.

Some of the practical consequences of the above in designing a gravityV ..ow system are :

a. Increasing pipe diameter between any two points will produce a largerflow of water between those two points.

b Adding many bends and fittings reduces the flow.c. Changing from QI to PVC pipe of the same diameter will result in aaincreased flow of wat er.

5 Pipe DesignIn designing a gravity flow pipeline the available he a d ^ obtained fromfield measurements. From the number of people to be served and the projected per capita consumption the desired flow of water is calculated.A pipe size is then choosen with a head loss less than the availablehead at the desired flow of water and pipe length. The head loss istaken from charts and tables, (see Section 't.H. and Appendix B)

/ and distance*are


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-A f -

6. Factors Affecting the Hydraulic Grade Line (HGL)In Figure A 3 the level of the water surface defines the hydraulic gradeline (HGL). ,jL'he slope of this line is constant for a given pipe diameterand given flow and is directly relnted to the head loss. Changing thepipe diameter of the How will change the slope of the hydraulic gradeline as in Fig. A *. Changing the amount of water flowing in the systemalso affects the HGL as in Fig. A 5. The HGL is compared with the groundprofile to determine if the pressure in. a pipeline is adequate. (Seeparagraph .


27/51

- B 1 -oA P P E N D I X B

IIEADLOSS CALCPLATIONS

1 . The Hear waterflew c al cu la to r i baaed the Calabrook-Whita for au la forf low la plp ea. It prev idea ae lu t ie ae ta th equ atiea for a wide rangef coad it ieaa withewt tha aee eae ity for cuaberaeae ea lc ul at io aa .la weiag tha a leu lat ar thara ara 5 va rl ab le e, they ara :a . H t ha haad la a a la a l l l l ba r a ; 98 a l l l lb a r a i s e qu iv a le a t t o

1 ae ter of haad. la pr aet le a whoa raadiag tha ca lcu lat or100 a ll l l b a ra can ba eoaaidered ao equiv alen t to 1 aatar haad*

b . F Co o f f lo la a t o f f r l c t i o a . Th ia la r a la t a d t o t ha p ipe a a t a r la laad oa tha calculator tho aaat eoaaoa typaa of plpo arc l iatad.

L Tha len gth of plpa which oa tho ca lcu la to r range a froa 1,5 to150 ,000 aatara .

D tho bora of plpo (plpo dla aata r) which oa the ca lcu la tor raageafroa 16 to 6,000 aa

3 1 the f low which oa the ca lc ul at or raagea froa 1 1/e to 1000 a3 /aIf aay four of tho above va ri ab le are kaowa or fixed thea the valu e ofthe f i f th var iable eaa be fouad oa the ca lculator .

2 . Example 1A aource la 2 kiloaetare fraa the village aad the differeaea la elevatieaiB 50 aettra, What will tha flow af water be if a 2" PVC pipe la inatailed?Coapare thia flow with the flow la a Z GI pipe.a. Sat the bore of pipe 51 aa opposite 2,000 aeterab.Sot tho plaatio pipe arraw oppooite the preaaura loaa of 5 bare (50 aetera)c. Read the flow for PVC pipe oppooite the flow arrow : 2,3 1/ad. Keep the bore of pipe 51 aa oppoaite 2,000 aeterae. Sat the 01 pipe arrow oppoaite the preaeure loaa of 5 baref. Bead the flow for GI pipe oppoaite the flow arrow : 1,8 1/aPleaae aee figure B-1 for aa illuatratioa of thia exaaple uaing thewater flow calculator.

3. Braaple 2A water aoaraa la 1,500 aetera froa the aaia reservoir in a village aad itla aeceaaajry to eoavay a flow of 1 1/a to it. GalTaplzed iron plpa auatbe uaed. The differeaea la elevation ia 35 aetera.What eise' pipe ia neceasary ?


28/51

o B - 3

fa*

a. Set the flow arrow at 1 1/sb. Set the arrow for galvanized iron pipe at 3,5 bare (35 meters)c. Read the bore of pipe opp osi te 1,500 m eters. It i s '1,5 mmor 1,63 i nches.

There ir no p ipe availa ble with a diameter of 1,63 inc hes. If we use 1,5inch pipe t he flow will be less than ^ 1/a if we use 2 " inch pip e the flowwill be more. Check as follows :

a. Set the bore of pipe 51 mm (2 in ches) oppos ite 1,500 meters.b . Set the arrow for galvanized iron pipe at 3i5 barsc. Read opposite the flow arrow 1,75 l/sd. >et the bore of pipe 3 8 mm (1,5 i nches) op pos ite 1,500 meterse. Set the arrow for galvanized iron pi pe at 3i5 barsf. Read opposite the flow arrow 0,8 l/s

Since 1,5 inches pipe is too small and 2 " pipe is too lapge a combinationof the two can be used. Try 750 meters 2 " pipe and 750 meters 1,5" pipe :

a. Set the bore of pipe of pipe 51 mm 2 " oppos ite 750 metersb . Set the flow arrow opposit e 1,0 l/sc. Read the pressure los s opposi te the galvanized iron arro w 650

millibars or 6,5 meters.d. Set the bore of pipe 3 8 mm 1,5" op posit e 750 meterse. Set the flow arr ow oppos ite 1,0 l/sf. Read the pressure lo ss opp osite the galvanized iron a rrow at

i^, 27 bars or 27 meters.

The tot al head lose for tl ; 1,500 meters then equals 2 7 + 6,5 o r 33,5 meters.This more closely matches the availabl e head of 35 meters.

H . k*The Mear Water Flow Calculator is available from :

M.H.Mear and Co. Ltd.56 Nettleton Roa d,Dalton,HuddersfieldEngland.


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- 3 '+ -

If a Mear Water Flow Calcul ator i6 not available then the headlosscan bo obtained from tub or.,ch.-irts, nom ogr ap hs, or direct cal culation using r. empirical formula, normally tables would he theeasiest to use and suitab le oner, can bo obtai ned from the pipe manufactur er or suppl ier. There may he slight differences in theheadloss es obtained using each of these methods but they will notbe significant. Any of the methods ar e acceptable and the one thatis most convenient should be chosen.

Tables of headloss factors for galvanized iron and PVC are presentedon pages B 6 and 3 7. Following the example on purer.B-1 and B-2 a water source is 1,500 meters from the reservoir andthe desired flow is 1 1/s . The difference in elevation is Y>meters.What size pipe is necessary ?SolutionSince the headless factors in the table are given in meters per 100meters {% )the avai labl e head should be converted to a percentageas follows :

35 meters (available head) _ ,,v = d JJfr1,500 meters (distan ce)Checking the tabl e it can bo seen that a headl oss factors of 2.33?'.will result in a flow of between 0. 75 and 0. 80 1/s if a 1/?" pipe isused. (The table does not have a headloss factor of exactly2.33?>but thi6 value l ies between2%15


30/51

B r

The length of the lar ge r pipe (I.) wi ll bo equ^l t o D - 5 .

In tho abovo example I = JyPL - \PP (for the dci i rr-d flow of 1 1/3)IT, - ;'..60 (fo r the deulrr-d flow of 1 l/ s )D =1,500

100 x J.5 - ( 0.8P. x l . r ^ )Thus 2 = " = ?r>\ metcro3.6 - O.P,ondL = 1,?00 - 7;i3 - 9

Note th*ttheva l ues o b t a i ne daronli ghtly different thanthevalue.';o b t a i ne d u s i n gtheKe.-ir Wat'jr Fl ow C al c u l a to rinexa m p le ?.onpa ge 3D-1and13-2. This di fferenc e, howevo r,is notni g n if i c t n tand is duet o c a l c u l a t i n ganexact head los sof 35meters w ithnoresi d u a l head .I n u n i n gthoMe;r:' lcul-


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- C 1 -oAPPENDIX CCONSTRUCTION NOTES

1. CAPTERING (SPRING PROTECTION)NOTES1.1. The construction of a captering will depend on the physical cha rac

teristics of the spring and surrounding area. Several possible situations are depicted in figures C1 , C2,and C3 . In addition the cons iderations in paragraph 1.2 - 1.16 below must be thoroughly understood and applied.

1.2. A captering has two primary functions : it collects and convey s thewater for distribution and it protects the water from contamina tion.It normally does not provide storage although this is sometimespossible. In many instances it is not feasible to excavate near thesource to provide storage capacity. A common error that occur s whena combination reservoir/captering is constructed is that most of thestorage is above the natural water level of the source. This canlead to prob lems . Therefore* it is better to convey the water fromthe source (protected are a) to a convenient location close by whereany necersary storage can be provided and the water supplied to thedistribution system.

1.3 It is best if the captering and source can be completely coveredwith a backfill or more than 1 meter of clay or other impermeablemater ial. A manhole may be constructed to allow access to the sourcebut it is not required. Several variations are shown in figuresC1,C2,and C3 .

1.A. In installing the foundation it is important to dig down to,but notthrough,the impermeable base layer. The water flow should be horizontalrather than upward through a permeable layer. The water level shouldnever be allowed to rise above this level.

1.5. The water level should not be allowed to rise above the originalnatural outflow of the spring. This level should be carefullyrecorded with some respect to some permanent nearby object. Any overflow or withdrawal must be below this level. Only upon the recommendation of an experienced hydrop;eologist should a higher withdrawalor overflow be installed. The danger is that allowing the water level to rise will create back pressure that may result in a reductionof yield or loss of the spring. Dozens of water systems in Indonesiado not function properly due to problems created by back press ure.


32/51

- C 2 -

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33/51

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34/51

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35/51

- c 5 -o

1.6. The foundation, wnlls, covering,and all joints should be watertight.1.7* There should be no trees or vegetation whose roots may eventually

enter and disturb the source protection. However, any existinglarge trees should be left undisturbed so as not to disturb thesource.

1.8. The outflow conduit from the captering should be large enough and ofsufficient slope to accommodate the maximum anticipated flow.

1.9. Arrangement should be made for diversion and drainage of any surfacewater.

1.10. If it is possible to stop the flow of water in the collecting pipethen there must be provision for an overflow of sufficient size.

1.11. If there is an overflow pipe then it must be of sufficient diameterand it must have a strainer. The open area of the strainer should be2-3 times the crosssection.ilarea of the overflow pipe. Openingsin the strainer should be small enough to prevent entry of smallanimals. The offtake in a water chamber or reservoir should alsohave a strainer.

1.12. If there is an overflow then there must be suitable arrangementsfor drainage of any excess water.

1.13. If water from the captering is channelled to a water chamber or storage reservoir then the overflow of the chamber/reservoir must be ata lower level than the inflow from the cap tering .

1.T*. The date of construction should be engraved somewhere on the structure and any buried structures should be identified by a small concrete marker.

1.15. In so far as po6sible the source should be protected from anydisturbance. Fencing is recommended for a distance of 10 meters inthe front of, 10 meters on either side, and 50 meters to the rearof the source. Frotection and/or reforestation of the catchmentarea should be strongly encouraged.

1.16. If possible, arrangements should be made so that the yield of thesource can be easily measured.
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- c 6 -

2.RESERVOIR CONSTRUCTION2.1. Reservoirs provide storage to offset fluctuating domand and low

Bource flow6. They may improve water quality through sedimentation if they allow for some retention time. They can also serveto break pressure in the system. Important considerations'in theirconstruction are listed below.

2.2, There should be a clean out pipe in each compartment of the reservoir.The cleanout should be placed at the lowest point, aand the floor ofthe reservoir should slope towards it. It is not necessary to havean expensive valve to control this. A simple plug is sufficient.

Joinings of the wall and floor should be slightly rounded to facilitate cleaning.

Any offtakes should be 5 to 20 centimeters above the reservoir floor.The larger the reservoir, the higher the level. The level of theofftakes with respect to the ground will depend on the usage of thereservoir.

2.5. The level of the inlet pipe should be approximately 10 to 20 cmbelow the cover of the reservoir. In smaller reservoirs(generallythose with an inflow pipe of 1" diameter or less) the inlet shouldbe fitted with a float vnlve so that the flow is stopped when thereservoir is full. The flont should be placed so that the flow isstopped before the water level reaches the level of the inlet pipe.In larger reservoirs an elbow or baffle maybe required to reduceturbulence. '

2.6. The inlet pipe should be fitted with a globe valve to control theinflow. The valve should be protected from possible tampering.

2.7.The overflow should be placed at a slightly higher level than theinflow so that it will come into play only if the float vnlve malfunctions. The overflow also serves as an air ventilation pipe.

2.8. The overflow pipe diameter should be large enough to accommodatethe maximum expected flow. It is normally larger than the inflowpipe because the inflow is under pressure. For example, an inflowpipe dT #** diameter might require an overflow of 1#" diameter.


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- C 9 -o

The pipeline must have washout valves at all low points.

Union joints in galvanized iron pipe should be installed at minimumevery 120 meters and near every fitting. In rough terrain they shouldbe installed at least every 50 mete rs. *

PVC pipe must be buried at least 50 cm below the natural ground level.

All QI pip* installed above ground should be secured and anchoredwith concrete pillars at suitable intervals. The installation ofpipe above ground has several advantages : it is not possible t"lose" the pipeline several years after installation : it may lastlonger due to reduced corrosion : and trenching is not mecessary.The disadvantages are : it is more subject to tampering and certainkinds of stress : and expensive concrete pillars are required forsupport.


38/51

- D 1 -Ar P E N D I X D

STEPS IN SURVEY AND DESIGN

The Field Survey1. Survey the source and the village; initiate contact with the commu

nity.

2.Jrom survey results decide on the feasibility of constructing thewater system.

3. ''or systems considered feasible a detailed survey of the source,distance, and ground levels is made, ^ome one from the village shouldassist in this. At this time tentative locations for distributionpoints are decided upon in consultation with the villagers, taking intoaccount their own wish es, population distribution,, etc.

The Design ProcessThe survey data is used to make preliminary design roughly as follows :1. Decide on general system design, type of distribution facilities,etc.2.Decide of how much of the population can be served by the system.

decide on per capita usage and calculate the average daily usage taking into account population growth.

3.Arom the type of system and average daily usage determine the desiredstorage and its placement. The placement of the distribution pointsmust be fixed at this time.

4. rom the placement of the distribution points make a general sketchof the system including all relevant distances and elevations. Basedon the population distribution the average daily flows required at eachpoint can be calculated and noted on the sketch.

5. T o m the average daily flews and the type of system the design flowsfor the pipe are selected. .

6. -rom the elevation profile and general scheme of the system the needand placement of _br*.-*k pressure tanks is determined-and recordedon the general sketch.

7.r'rom the design flows and elevations the head losses for various diameter pipes are calculated for each unbroken section of the pipeline.

8. The most appropriate pipe is chosen for all sections of the pipelinebased on the calculated head looses. The hydraulic gradients are thenplotted on the profil e. Pipe diameters should be changed where necessary in order to eliminate any negative pressures.

9. Detailed" drawings, specifications, materials lists and budgets cannow be prepared.


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- E 1 -oA P P E N D I X ESAMPLE DKT.IGN FOR DESA GEMBIRA

1. General1.1. The village of Desa Gembira has a population of 850 divided into

two kampongs, Gembira I with 605 persona and Gembira II with 2^5persons. A water Bource with an estimated minimum flow of 1 1/sis located approximately 2,30 meters from the vill age. A sketchmap of the village and a ground profile are presented in FiguresB1 to FA,

2.Design Parameters2.1.Population

The design population will be the expected population in 10 yearsat a 2# growth rate or 850 x 1.22 equal to 1,037 perso ns. For designpurposes this may be rounded up to 1,050 persons.

2.2.Water UsageIt is preferable to supply the maximum amount of water possible buta per capita supply of 100 liters per day would require 105,000liters/day or a flow of 1.2 1/s. Since the estimated minimum flowof the source is only 1 1/s this is not possible. A per capitause of 80 liters/day would require an average daily flow of 0.971/s and this is possible.

2.3. Storage RequirementsA per capita use of 80 liters/day means that the average daily usageis 80 x 1,050 or S4,000 liters. In order to reduce the size of themain pipe storage will be located in the village. The recommendedstorage is then one half of 84,000 liters or kz m3. Based on thepresent population distribution 245 -r 85O x 4 2 m3 or 12.1 m3 shouldbe in Gembira II and 605 *T 850 x 42 m3 or 29.9 m3 should be in Gembira I. Based on the village sketch it has been decided that thewater will be distributed to 5 public reservoirs, three in GembiraI and two in Gembira II . The three reservoirs in Gembira I will be10 m3 each for a total of 30 m3 (rounded up from 29.9 3)' 'he two reservoirs in Gembira II will be 6 m3 each for a toral of 12m3 (rounded down from12.1 m3). with this distribution of reservoirsno one has to walk more than 100 meters to obtain water.

2.4. Number of" FaucetsThe number of persons per faucet should be between 30 and 100 sothe number of faucets for Gembira I should be between 6 and 20


40/51

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41/51

- E 3 -

and for Gembira II between 2 and 8. In order to facilitate usagea higher nu mber i s preferable. Thus 6 faucets at each of the 3 reservoi rs in Gembira I and '+ faucets at each of the reservoir s in Gem-bira II give a total of 26. The average number of persons per faucet is k2 for Gembira I and 37 for Gembira II . Half of the faucetscan b e placed on o ne side of the reservoir and half on the oppositeside. ThuSjOne area can be used by females and the other by mal es.

2. 5. Uesign FlowsThe path of the pipeline is sketched in Figure E1 . The water willflow continously into the reservoirs so the design flows will be thesame as theaver,ge daily flows. At the projected per capita useof 80 1/day the average daily flow is 0.97l/o but the spring has anestimated min imum flow of 1.0 1/e. Therefore,1.o l/s can also beused in designi ng the pip eline.

From the source to the junction at point A the design flow used is1.0 1/e. At point A this flow is divided with 0.71 l/s flowingto Gembira I and reservoir D. The remainder of0.29l/s will flowto Gembira II and reservoir E. At reservoir B 0.23 l/a is taken and theremainder of O . W l/s flows to reservoir C. At C 0.2k l/s is takenand the remainder of0.?'+l/s flows to reservoir D. *t reservoirE 0. 1^ l/s is taken and the remainder of 0.15 l/s flows to reservoirF. The design flows are noted on the pipeline route and profile.

3. pipeline Design3.1. Pressure Release Tnnk6

Inspection of the profiles in Fig . E 2 to E ^ indicated that a pressure''' release tarfk is necessary 1,300 meters from the sou rce. The stat ic

headat this point is 55 meters. The point of greatest pressure is1,100 meters from the source but it is not po ssibl e to place the tankat this pointbecause the water will not flow froa it up the adjacenthill.

3 . 2 . P i p e M a t e r i a lGalvanised iron pipe will be used d ue to difficulties in buryingmany sections.

33 Pip e ^>ize from Sou rce to P ressure Kelease TankThe distance to the tank is 1,300.ro and the availabl e head 55 m wit ha design flow of 1.0 l/s. Calculated head lbsses are as follows :
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42/51

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43/51

P O J U V A

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44/51

FIGURE 4

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45/51

-


46/51

- v.8 -a

From Point A to jfenervoir B n 1.5 inch pipe is appropriate. From reservoir B to C a 1.25 inch pipe ir, adequate and there is extra headavailable of 10 - 5 = 5 meters, oince reservoirs C and D are at thesame elevation this head wil] allow the water to flow to reservoir D.Thus between reservoirs H and D the total calculated head loss is 10meters and the total available head in.also 10 asters.

3.6. Foint A to Reservoir E and FCalculated head losses are as follows :length(meters)

600600600200200

now(l/s)0.290.290.290.150.15

Fipr? diameter(inches)

1.51.251.01.00.75

361927.5

head loss Available head(incl.10# extra) (meters)(meters)77733

If 1.25 inch pipe is used from point A to reservoir E and 1.0 inchpipe from reservoir E to F then the total head loss is 6 + 2 or 8meters which closely matches the available head of 10 meters. The pipesizes,HGL, and design flows are all noted on the profile.


47/51


48/51

- F 2 -

Estimated Minimum Flow : The beat estimate of the ten year low flow* from thewater source that can be made with the available data.Often the lowest point measurement taken reduced byan appropriate factor taking into account all relevantfactors. It is beet to be conservative in estimatingthe minimum flow to be used in designing the system*

Coli : See Fecal Col ifoms

Fecal Coliforms :Also referred to as Escherichia Coli or E. Coli. Theseare part of the coliform group but the fermentationtest is conducted at M C. At this temperature thenon-fecal organism die from heat shock* It is believedthat all fecal coliforme originate in the intestines ofman and higher mammals and that they will not reproduceoutside the host* 'here is some evidence that this doesnot hold true for tropical areas but until further research is completed the presence of fecal coliforms mustbe regarded as evidence of fecal contamination. Fecalcoliforms themselves are usually not harmful to manbut their presence indicates that the water may containdisease causing organisms which may cause illness inthose who consume it*

: A ralue or rule derived from known facts or figures tobe used in decision making or designing. The decisionmaker may choose to deviate from the guideline. Thisis opposed to a standard or criteria which is generallya rule established by authority that cannot be deviatedfrom.

H e a d j The pressure or force per unit area that is availableor must be overcome in order to transport water. Headmay be supplied by gravity or by mechanical means such asa pump. Although it is a pressure it is generally referred to in meters or feet which is the equivalent pressurethat would be exerted by a standing column of water ofthat height.

Guideline


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o - F ? -Bead loos : A loss of pressure (or head) in a closed pipeline due to fric

tion between the pipe and the flowing water. The head lossincreases if the volume of water increases, if the distanceit is carried increases, if the diameter of the pipe is madesmaller, or if the inside surface of the pipe is rougher.Calculated head losses are compared with the available headto determine if the desired flow of water will be obtainedunder conditions given.

: A method for determining concentrations of coliforms and/or fecal coliform bacteria in water sample. The watersample is filtered through a small membrane that retainsthe bacteria. The bacteria on the membrane are then cultured (allowed to grow) for 2^ hours at a set temperaturein an incubator. The number of bacteria colonies growingare then counted and related to the volume of water filtered to estimate the concentration of bacteria in the original water sample.

Peak Usage j The highest flow of water expected to occur on any given day. This flow usually lasts for only a very shorttime period and does not necessarily occur every day.For designing standpipe systems it is taken as four timesthe average daily flow.

Point Measurements: Measurements of flow,quality etc. taken at one instant intime. These measurements represent the actual conditionpnly at the exact time of taking the measurement. Wherecontinous monitoring is not possible then a number ofpoint measurements are used to estimate other quantitiesof interest such as the average flow, highest yearly flow,ten year low flow etc.

Q : A general symbol used by engineers to represent the quantityof water flowing. It could represent any flow such as thatof a spring, river, or pipeline etc. It is normallyexpressed in liters per second or cubic meters per day.

Membrane FilterTechnique

Standards : See guidelines


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- F If -oThe various pressures that would be obtained in the watersysten if it were full of water and the water is notflowing. It is different for each point in the systemand depends on the eleration relative to the highest pointin the system. It is the same as the available head*

The lowest flow fro* the water source that is expectedto occur, on the average, once every ten yea rs.


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LENGTH

APPENDIX 0CONVERSION FACTORS55

1 meter = 3,28 feet1 inch =2,5 cm = 25.^ mm

AREA :VOLUME :

Incheoo,50,751,01,2521,51 square cm1 liter1 liter

*

m1 cubic meters1 cubic meter1 US Gallon1 imperial i

s

mm131925325138

0,1551,0000,26'1,00026* U

square

inches2,53'56

inchescubic centimetersU.S.Gallonsliters. gollo

3.79 lit ersgallon 1.2 U.S

ns

. gallons

mm6'76102127152

FLOW 1 1/s (liter/second) = R6.U00 1/day1 1/s = 15,8 U.S . gnl/min 22,800 OS gal/day1 US gal/min = 227 liters/hour1 1/s = 86 liters/day/person for 1,000 people0,5 1/s s *

practical design notes

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