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IS : 1742 1993Indian Standard

CODE OF PRACTICE FORBUILDING DRAINAGE( Second Revision )

Second Reprint JULY 1995

UDC 696*12/13 : 00676

% ...0 Copyright 1984 i,..::I .BUBEAU OF INDdN STANDARD~bMANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG

( Reaffirmed 1996


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IS : 1742 1983

Indian StandardCODE OF PRACTICE FOR

BUILDING DRAINAGE( Second Revision )

Water Supply and Sanitation Sectional Committee, BDC 24Chairman Representing

SHRI J . DCRUZ Water Su pply an d Sewage Disposal Und erta king,New DelhiMembers

CHIEB EN QINE ER ( CIVIL I ) ( Alternate t oShr i J . DCru z )ADVISER ( PH E ) Ministry of Works an d Housing, New DelhiDEP UTY ADVISER ( PH E ) (Alter na te )SHBI N. S. BHAIRAVAN Public Health En gineering Departm ent, Govern-ment of Kerala, TrivandrumSUPEBINTENDINQ NGINEER ( Alternate )SHRI I. CHANDBA Pu blic Works Depart men t, Pu blic Health Bran ch,

SHRI K. K. GANDHI ( Alternate) Governmen t of Har yana, Chan digarhCHIEF ENGIN EE R ( CONSTKUCTION) Utta r Pra desh J al Nigam, LucknowSUPERINTENDINO YQINEER ( Alternate )Snnr R. C. P. CHAUD~ARY Engineers India Ltd, New DelhiSHRI H. V. RAO ( Alternate )SHRI S. K. DAS~~PTA Calcut ta Metropolitan Development Aut hority,CalcuttaSHRI S. R. MUKHERJEE ( Alternate )PROF.J. M. DAVE Inst itut ion of En gineers ( India ), Calcut taSHRI S. G. DEOLALIKA~~. In personal capa city ( Flat No. 403, Savitri CinemaCommerical Complex, .New Delhi )

SHRI B. R. N. GUP TA Ministr y of Defence, En gineer -in-Chiefs Bra nch,Army HeadquartersSHRI K. V. KI~ISHNA~CJ HTHY( Alternale )HYDRAULIC E~GISEER Municipal Corporat ion of Great er Bombay,BombayCHIEP EKGINEEK ( SEWERAGEPROJ ECTS: ( Alfcrt &e )( Continued on page 2 )

0 Copyright 1984BURE AU OF INDI AN STANDARDS

This publicat ion is protected un der th e Itzdinn Copyright Act ( XIV of 1957 ) andrepr oduction in whole or in par t by an y mean s except with writt en perm ission of th epublisher shall be deemed to be an infringement of copyright un der th e said Act. I


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( Continwd from page1 )Members

SEW R. A. KHANN~Representing

Public Health Departmen t, Government ofMadhva Pra desh. BhonalSHRI D. K. MITRA (Alternate I )SERI I. S. BAWEJA ( Alternate II )SEBI P. KRISHNAN Centr al Public Works Depart men t, New DelhiSUIWEYOR OF WORKS-~ ( NDZ ) ( Alternate )SH IZI M. Y. MADAN The Hindu sta n Const ru ction Co Ltd, Bomba ySHRI C. E. S. RAO ( Alternate )SERI S. L. MAINI Pu blic Works Depart ment , Pu blic Health Bra nch,Govern men t of Pu niab. P atialaSHRI R. NATARAJAN Hindu stan Dorr -Oliver-L&l, Bomba ySHRI B. M. RAHUL ( Alternate )PBOB K. J . NATH All India Inst itut e of Hygiene an d Pu blic Health ,CalcuttaSHRI D. GUIN ( Alternate )

PBO~ V. RAMAN National Environment al En gineering ResearchInst itute ( CSIR ), Na gpurSH RI S. R. KSRIRSA~AR ( AIlern otc )SHRI RANJIT SIN~H Ministr y of RailwaysDR A. V. R. RAO Nat iona l Bu ildings Organ izat ion, New DelhiSH RI 0. P. RATRA ( Alternate )SECRETARY Indian Water Work s Association, BombaySECRETARY GENE RAL Inst itution of Pu blic Health En gineers India,CalcuttaSHRI R. N. BANERJ EE ( Alternate )SHRI L. R. SEH ~AL L. R. Sehga l & Co, New Delh iSHRI S. K. SHAKMA Centr al Building Research Inst itute ( CSIR ),RoorkeeSHRI B. N. THYA~ARAJA Banga lore Water Supp ly and Sewerage Boar d,Bangalore

SERI H. S. PUTTA~EXPANNA ( Alternate )SHRIV.VARADARAJAN Madra s Metropolita n Water Supp ly an d SewerageBoard. Madras

SH RI S. DAIVAXANI ( Alternate)SH R~ G. RAMAN. Director Genera l, IS1 ( Ex-o$icio Member )Director ( CivEn gg )Secretary

SHRI A. K. AVASTHYAssista nt Dir ector ( Civ En gg ), IS1

Drainage Subcommittee, BDC 24 : 2Conuener

SHRI P. G. JOSHIMembers

Mun icipal Corporat ion of Great er Bombay,BombayDEPUTY CHIE F EN QINEE R ( SEWERAGE )( Alternate to Shri P. G. Joshi )

AynWc;;;;; CHIEF EN Q~NEE R Delhi Municipal Corpora tion, New DelhiDEPUTY DRAINAGE ENGINEER (Alternate) ( Continued on page 50 )

II2


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Indian StandardCODE OF PRACTICE FOR

BUILDING DRAINAGE( Second Revision )0. FOREWORD

0.1 The Indian Standard ( Second Revision ) was adopted by the IndianStandards Institution on 30 November 1983, after the draft finalized bythe Water Supply and Sanitation Sectional Committee had been approvedby the Civil Engineering Division Council.0.2 This standard, published in 1960 and subsequently revised in 1972 wasintended to bring out a long felt uniformity in the variety of drainagepractices followed by various Municipal Corporation, Municipalities andother bodies in the country in efficient drainage of surface and subsoilwater and sewage from buildings to public sewers. It is being revised toincorporate improvements found necessary in the light of the usage of thestandard.0.3 This code of practice represents a standard of good przctice and, there-fore, takes the form of recommendations.0.4 For the purpose of deci,ding whether a particular requirement of thisstandard is complied with, the final value, observed or calculated, express-ing the result of a test or analysis, shall be rounded off in accordance withIS : 2-lC,60*. The number of significant places retained in the rounded offvalue should be the same as that of the specified value in this standard.

1. SCOPE1.1 This code gives recommendations for the design, layout, constructionand maintenance of drains for waste water, surface water and subsoilwater and sewage together with all ancilliary works, like connections,manholes, inspection chambers, etc, used within the building and from thebuilding to the connection to a public sewer or to treatment works, acesspool, a soakaway or a water course.

*Rules for roundiilg off numerical values ( wi s e d ) .3


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IS :1742 - 19852. TJ UUWINOLOGY2.0 For the purpose of this standard, the following definitions shall apply.2.1 A u t h o r i t y - An individual, an official, a board, a department or anagency established and authorised by Union or State Government or anystatutory body created by law who undertakes to administer and enforcethe provisions of this code as adopted or amended.2.2 B a r r e l - That portion of a pipe in which the diameter and wall thick-ness remain uniform throughout.2.3 B e d d i n g - The material on which the pipe is laid and which providessupport for the pipe. Bedding can be concrete, granuIar material or theprepared trench bottom.2.4 B e n c h i n g - Sloping surfaces constructed on either side of channelsat the base of a manhole or inspection chamber for the purpose ofconfining the flow of sewage, avoiding the accumulation of deposits andproviding a safe working platform.2.5 Chair - A bed of concrete or other suitable material on the trenchfloor to provide a support for the pipes at intervals.2.6 C h a n n e l - The open waterway through which sewage, storm wateror other liquid waste Aow at the invert of a manhole or an inspectionchamber.2.7 Cleaning Eye - An access opening in a pipe or pipe fitting arrangedto facilitate the clearing or obstructions and fitted with removable cover.2.8 Connection - The junction of a foul water drain, surface waterdrain or sewer from building or buildings with public sewer treatmentworks cesspool, soakaway or other water courses.2.9 Cover -

a) A removable plate for permitting access to a pire to a fittingvessel or appliance.b) The vertical distance between the top of the barrel of a buried

pipe or other construction and the surface of the ground.2.18 Depth of Manhole - The vertical distance from the top of themanhole cover to the outgoing invert of the main drain channel.2.11 Diameter - The nominal internal diameter of a pipe.2.12 Drain - A conduit or channel for the carriage of storm water,sewerage or other used water.

4


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lSt1742-19832.13 Drainagethe purpose.

- The r emoval of an y liquid by a system cons tr ucted for

2.14 D ra i n a g e Wo rk - The design an d const ru ction of a system ofdrainage.2.15 D r o p C on n e c t io n - A length of condu it ins ta lled vert icallyimmediate1 y before its conn ection to a sewer or to an oth er drain.2.16 D ro p M a n h o le - A inan hole installed in a, sewer where th e eleva-tion of th e incoming sewer cons idera bly exceeds th at of th e outgoing sewer ;a vertical wat erway out side t he ma nh ole is provided to divert th e wastewat er from t he upper to th e lower level- so th at it does not fall freely intoth e ma nhole except at peak r at e of flow.2.17 F o r m a t i o n - The finished level of th e excava tion at th e bottom ofa trench or heading prepared to receive the perman ent work.2.18 Fr ench Drain o r R u b b l e D r a i n - A sha llow tr ench filled withcoar se ru bble, clinker , or similar ma ter ial with or with out field dra in pipes.2.19 Gully Cha mber -tr ap for housing th e sam e.

The cha mber built of ma sonr y round a gully

2.20 Gully T r a p - It is a tr ap provided in a dra inage system with awat er seal fixed in a suit able position to collect was te wat er from th e scul-lery, kitchen sink, wash basins, baths and rain water pipes.2.21 Ha un ching - Out war d sloping concret e su pport to th e sides of apipe or cha nn el above th e ctincrete bedding.2.22 Highwa y Auth orit y - The public body in which is vested , or whichis th e owner of a highwa y repa ira ble by th e inha bitan ts collectively;other wise th e body of persons resp onsible for the up keep of th e highwa y.2.23 Inspection Cham ber - A wat er-tight cha mber const ru cted in an yhouse-dra inage system which ta kes wastes from gully tr aps an d disposes ofto ma nh ole with access for inspection an d maint enan ce.2.24 Int erceptor Manh ole or Int erceptor Cham ber - A manholeincorporat ing an inter cepting tr ap, and providing mean s of access th ereto.2.25 Inver t - The lowest p oint of th e int ern al s ur face of a pipe of cha nn elat any cross section.2.26 Ju nction Pipe - A pipe incorpora tin g one or more bra nches.2.27 Man hole - An open ing by which a ma n ma y ent er oi- leave a dra in,a sewer or other closed stru cture for inspection, cleaning and other main-ten an ce opera tions, fitted with a suitable cover.

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2 2 8 M a n h o l e C h a m b e r - A chamber constructed on a drain or sewerso as to provide access thereto for inspection, testing or the clearance- ofobstruction.2.29 P i p e S y s t e m s - The pipe systems as defined in IS : 5329-1983*.2.30 R e s t R e x a d o r D a c k -F o o t B e n d - A bend, having a foot formedintegrally in its base, used to receive a vertical pipe.2.31 Saddle - A purpose made fitting, so shaped as to fit over a hole cutin a sewer or drain and used to form connections.2.32 Sewer - A pipe or conduit, generally closed, but normally not flow-ing full for carrying sewage or other waste liquids.2.33 Soak-away - A pit, dug into permeable ground lined to form acovered perforated chamber or fil led with hard-core, to which liquid is led,and from which it may soak away into the ground.2.34 S lo p H o p p e r ( S lo p S i n k ) - A hopper-shaped sink, with a flush-ing rim and outlet similar to those of a WC pan, for the reception anddischarge of human excreta.2.35 SoflGt - The highest point of the internal surface of a.sewer orculvert at any cross section.2.36 Soil Waste - The discharge from water closets, urinals, slop sinks,stable or cowshed gullies and similar appliances.2.37 Soil P i p e

a) In plumbing, a pipe that conveys the discharge of water closetsor fixtures having similar functions, with or without the dischargesfrom other fixtures.b) A standard type of bell-and-spigot cast iron pipe of limitedstrength.

2.38 S u b s o i l W a t e r - Water occurring naturally in the subsoil.2.39 Subsoil W a t e r D r a i na) A drain intended to collect and carry away subsoil water.

b) A drain intended to dssperse into the subsoil the eff luent from aseptic tank.2.40 S u r f a c e Wa t e r D r a i n - A drain conveyiig surface water includingstorm water.2.41 S y s t e ms o f D r a i n a g e

2.41.1 Combined System - A system of drains or sewers in which foulwater and surface water are conveyed by the same pipes.

*Code of practice for sanitary pipe work above ground for buildin@ (JirJt revirion,6


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IS f 1742 - 19832.41.2 Separate System - A system of drains or sewers in which thefoul water and surface water are conveyed by separate pipes.2.41.3 PartiaUr Separate System - A modification of the separatesystem in which part of the surface water is conveyed by the foul sewersand drams.

242 T r a d e E fflu e n t - Any liquid either with or without particles ofmatter in suspension therein, which is wholly or in part produce in thecourse of any trade or industry, carried at trade premises. It includes farmwastes but does not include domestic sewage.2.43 V e n t P i p e - An open ended pipe, in a hot water apparatus, for theescape of air and for the safe discharge of any steam generated.2.44 Ven t i la t i n g P ip e - A pipe in a sanitary pipework system whichfacilitates the circulation of air within the system and protects trap seaIsfrom excessive pressure fluctuation.2.45 Wast e Wat er ( Su l lage ) - The discharge from wash basins, sinksand similar appliances which does not contain human excreta.2.46 Was te P ip e - In plumbing, any pipe that receives the discharge ofany fixtures, except water closets or similar fixtures and conveys the sameto the house drain or soil or waste stack. When such pipe does not connectdirectly with a house drain or soil stack, it is called an indirect waste pipe.2.47 P u f f Ven t i la t i on - The ventilation provided for waste traps in two-pipe system, in order to preserve the water seal.3. MATE RIALS, F ITTIN GS AND SANITARY AP P LIANCES3 . 1 S tan d a r d s - All materials and fittings used in the construction of anyof the works or any of the appliances described in this code shall conformto the latest editions of the relevant Indian Standard specifications whereavailable in so far as these standards are applicable. Where no suchstandards exist, the materials, fittings and appliances shall be of the bestquality and workmanship, and shall be open to inspection by the purchaserat the manufacturers works before despatch.4. DESIGN CONSIDERATION4.1 Aim - In designing a drainage system for individual building(s), theaim shall be to provide a system of self-cleansing conduits for the convey-ance of soil, waste, surface or sub-surface waters, and for the removal ofsuch wastes speedily and efficiently to a sewer or other outlet without riskof nuisance and hazard to health.


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IS : 1742 - 19834.1.1 To achieve this aim, a drainage system shall satisfy the followingrequirements:

4b)44e)

4.1.2

Rapid and efficient removal of liquid wastes without leakage;Prevention of access of foul gases to the building and provisionfor their escape from the system;Adequate and easy access for cleaning and clearing obstructions;Prevention ofundue external or internal corrosion, or erosion ofjoints and protection of materials of construction; andAvoidance of air locks, siphonage, proneness.- to obstruction,deposit and damage.The realization of an economical drainage system is aided by_compact grouping of fitments in both horizontal and vertical directions.This implies that if care is taken and ingenuity brought into play whendesigning the original building or buildings to be drainage, it is possibleto group the sanitary fittings and other equipment requiring drainage,both in vertical and horizontal planes as to simplify the drainage systemand make it most economical.

4.2 P r e l i m i n a r y D a t a fo r D e s ig n4.2.1. General - Before the drainage system for a building or group ofbuildings is designed and constructed, accurate information regarding thesite conditions is essential. This information may vary with the individual

scheme but shall, in general, be covered by the following:a) Site plan - A plan of the site to scale 1 : 500 ( see IS : 965-1963* ) with reduced levels preferably related to Great Trigono-metrical Survey Datum indicating the position and lowest floorlevel of the proposed buildings, formation level, level of the out-fall, location of wells, underground sumps and other drinkingwater sources.b) Detailed plans - Plans and sections of the proposed buildingsto scale 1 : 100 showing the positions and types of all sanitaryfittings and other equipment requiring drainage, the location andextent of all paved areas and the position of all rain-water downpipes.c) Use - A description of the use for which the building is intendedand periods of occuption, in order that peak discharge may beestimated.d) The availability of sewers or other outlets and their levels,

*Equivalent metric units for scales, dimensions and quantities in general constructionwork ( revised .8


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IS : 1742 x983e) Bye-laws - The requirements of local bye-laws in regard to the

f 1

d

h)

3

drainage and sewerage.The nature of the sewage to be carried. While dealing withsewage from domestic premises or schools, special problems underthis head may not arise; however, note shall be taken of anypossibiiity of trade effluents being discharged into the pipes at afuture date.Cover - The depth below ground of the proposed sewers anddrains and the nature and weight of the traffic on the groundabove them.Subsoil knditions - Except for such minor works as housedrains, the fullest possible information shall be obtained as to thephysical and chemical nature of the ground to be excavated.Subsoil conditions govern the choice of design of the sewer ordrain and the method of excavation. The approximate level ofthe subsoil water, and any available records of flood levels shal!be ascertained, as also the depth of the water table rebtive to allsewer connections, unless it is known to be considerably below thelevel of the latter. In the case of deep manholes this informationwill influence largely the type of construction to be adopted. Theprobable safe bearing capacity of the subsoil at invert level shallalways be ascertained in the case of a deep manhole. Wherework of any magnitude is to be undertaken, trial pits or boreholesshall be put at intervals along the line of proposed sewer or drainand the data therefrom tabulated together with any informationavailable from previous works carried out in the vicinity. In general,the information derived from trial pits is more reliable than thatderived from boreholes. For a long length of sewer or drain,information derived from a few trial pits at carefully chosen pointsmay be supplemented by that obtained from a number of inter-mediate boreholes. Much useful information is often obtainedeconomically and quickly by the use of a soil auger. The positionsof trial pits or borehoies shall be shown on the plans, togetherwith sections showing the strata found and the dates on whichwater levels are recorded.

Location of other services - The position, depth and size ofall other pipes, mains, cables, or other services, in the vicinity ofthe proposed work may be ascertained from the authority, ifnecessary.9


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15:1742- 19834

4

PI

4)

Reinstatement of surf&es- Information about the requirementsof the highway authority is necessary where any part of thesewer or drain is to he taken under a highway. Those responsiblefor the sewer or drain shall be also responsible for the mainten-ance of the surface until permanently reinstated. The writtenconsent of the highway authority to break up .the surface andarrangement as to the charges thereof atid the method and the typeof surface reinstatement shall always be obtained before any workis commenced.Diversion and cont rol of trafic - In cases where sewers crossroads or footpaths, co-operation shall be maintained with thepolice and administration authorities regarding the controland diversion of vehicular and/or pedestrian traffic as may benecessary. Access to properties along the road shall always bemaintained, and adequate notice shall be given fb the occupiersof any shops or business premises, particularly if obstruction islikely.During the period of diversion, necessary danger lights, red flags,diversion boards, caution boards, watchmen etc., shall be providedas required by the authority.W ayleaves ( easement s ) - The individual or authority, carryingout the work is responsible for negotiating wayleaves where thesewer crosses land in other ownership. The full extent andconditions of such wayleaves shall be made known to the con-tractor and his employees, and prior notice of commencementof excavation shall always be given to the owners concerned andco-operation with them shall be maintained at all stages.

Where sewers run across fields or open ground, the exactlocation of manholes shall be shown on wayleave or easementplans. The right to maintain the sewer shall be specifically includedin any wayleave or easement arrangements which may be madewith the owner of the land.Damage to buildings and st ructures - When sewer trenches have tobe excavated neal buildings or wails a joint inspection with theowners of the property shaii be made to establish whether anydamage or cracks exi-t before starting the work, and a properlyauthenticated survey and record of the condition of buildingslikely to be affected shall be r.lade. Teil talcs may be placedacross outside cracks and dated, and kept under observation.Unretouched photc,graphs taken hy an independent photographer

- may provide useful evidence.10


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IS:1742 -19834.2.2 Drainage into a Public Sewer - Where public sewerage is availablethe following information .is particularly necessary and may be obtainedfrom the Authori,ty:

4b)44e)f 1

The position of the public sewer or sewers in relation to theproposed buildings;The invert level of the public sewer;The system on which the public sewers are designed ( combined,separate or partially separate ), the lowest level at which connec-tion may be made to it, and the authority in which it is vested;The material of construction and condition of the sewer if connec-tion is not to be made by the authority;The extent to which surcharge in the sewer may influence thedrainage scheme;Whether the connection to the public sewer is made, or any partof the drain laid by the authority, or whether the owner is respon-sible for this work; if the latter, whether authority imposes anyspecial conditions;

!44

Whether an intercepting trap is required by the authority on thedrain near the boundary of the curtilage; andWhere manholes are constructed under roads, the approval of thehighway authority to the type of cover to be fitted shall beobtained.

4.2.3 Ot her Methodr of Disposals of Sewage4.2.3.1 Where discharge into a public sewer is not possible, thedrainage of the building shall be on the separate system. Foul water shallbe disposed of by adequate treatment approved by the authority at the site.The effluent from the plant shall be discharged into a natural water courseor on the surface of the ground or disposed of by subsoil dispersion, prefer-ably draining to a suitable outlet channel.4.2.3.2 In the case of dilution into a natural stream course, thequality of effluent shall conform to the requirements of authority control-ling the prevention of pollution of stream. For guidance IS : 4764-1973*and IS: 4733-1972-/- may be followed.4.2.3.3 In the case of subsoil dispersion, the requirements of theauthority for water supply shall be observed to avoid any possible pollutionof local water supplies or wells.

*Toierance limits~ or sewage effluents dirchargcd into inland surfacr waters (firsirmision .tMe?hods of sampling and test for sewage elfluenrs iJr -t rerision ).11


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IS : 17 42 - 198 34.2.3.4 The general subsoil water level and the subsoil conditionsshall be ascertained including the absorptive capacity of the soil.4.2.3.5 A subsoil dispersion is not desirable near a building or in suchpositions that the ground below the foundations is likely to be affected.4.2.3.6 Where no- other method of disposal is possible, foul watermay be collected and stored in impervious covered cesspool and arrange-ments made with the authority for sat@factory periodical removal andconveyance to a disposal works.4.2.3.1 Under the separate system, drainage of the building shall bedone through septic tank of different sizes or by stabilization ponds or byany other methods as approved by the authority.

4.2.4 Disposal of Surface and Subsoil Water - All information which mayinfluence the choice of methods of disposal or surface and/or subsoil watersshall be obtained. In the absence of surface water drainage system andif practicable and permissible, disposal into a natural water course orsoakaway may be adopted. The location and flood levels of the watercourse as aiso the requirements of the authority controlling the river or thewaterway shall be ascertained.4.3 L a y o u t

4.3.1 General - Generally, rain water shall be dealt with separatelyfrom sewage and sullage. Sewage and sullage shall be connected to sewers.Storm water from courtyard may be connected to the sewer where it is notpossible to drain otherwtse after obtaining permission of the authority.

4.3.1.1 The layout shall be as simple and direct as practicable.Considerations shall be given to alternative layouts so as to ensure that themost economical and practical solution is adopted. The possibility ofalterations shall be avoided by exercising due care and forethought.4.3.1.2 The requirements of sanitary appliances and fitments as wellas the basic requirements for water supply, drainage and sanitation shallbe in accordance with IS : 1172-1983*.

4.3.2 Protection Against Vermin and Dirt - The installation of sanitaryfittings shall not introduce crevices which are not possible to inspect andclean readily. Pipes if not embedded shall be run well clear of the wall.Holes through walls to take pipes shall be made good on both sides toprevent entry of insects. Materials used for embedding pipes shall berodent-proof. Passage of rodents from room to room or from floor to floorshall be prevented by suitable sealing. The intermediate lengths of ducts*Code of basic requirements for water supply, drainage and sanitation ( third

revision .12


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Is:1742-1993

and chases shall be capable of easy inspection. Any unused drains,sewers, etc. shall be demolished or filled in to keep them free fromrodents.4.3.3 Choice of Plumbing System - Sanitary pipe work in buildings shallconform to the requirements given in IS : 5329-1983*.4.3.4 Additional Requirements - The pipes shall be laid in straight .linesas far as possible and with uniform gradients. Anything that is likely tocause irregularity of flow, such as, abrupt changes of directions shall beavoided. No bends and junctions whatsoever shall be permitted insewers except at manholes and inspection chambers.

4.3.4.1 Where it is not possible to avoid a change of direction in thecase of drains, access shall be provided through manholes and inspectionchambers. Necessary terminal bends at junctions shall be l/8 or prefer-ably l/16 bends.

4.3.4.2 All junctions shall be oblique and the contained angle shallnot be more than 60.4.3.4.3 Drains may be laid under the buildings only when unavoi-dable and when it is not possible to obtain otherwise a sufficient fall inthe drain.4.3.4.4 Where it is necessary to lay a drain under a building orexposed locations within the building, the following conditions shallbe observed:4b)44e)

Pipes shall be of cast iron ( see IS : 1536-1976t and IS : 1537-1976$ );The drains shall be laid in a straight line and at a uniformgradient;Means of access in the form of manholes/inspection chambersshall be provided at each end, immediately outside the building;In case the pipe or any part of it is laid above the natural surfaceof the ground, it shall be laid on concrete supports the bottom ofwhich goes at least 150 mm below the ground surface; andIt is desirable that drains should not be taken through a livingroom or kitchen and shall preferably be taken under a staircaseroom or a passage.

*Code of practice for sanitary pipe work above ground for buildings ( jint revision ).tSpecification for centrifugally cast ( spun ) iron pressure pipes for water, gas andsewage ( second revision ).JSpecification for vertically cast iron pressure pipes for water, gas and sewage

( first rcuision ).13


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4.3.4.5 Surcharge of sewers (precautzons ) -Where there is a risk ofthe sewer becoming surcharged under storm conditions all gullies andsanitary fittings shall be located above the level of maximum surchargeof the sewer. Where this is not practicable, an anti-flood valve shall beprovided in the manhole nearest to the junction of the drain and sewer.Parts exposed to wear in anti-flood valves shall be of non-corrodablemetal and easily accessible. The cross-sectional area of flow through thevalve shall not be less than that of the pipe connected. In extreme cases,pumping may have to be considered.

4.3.4.6 The distance between inspection chamber and gully chambershall not exceed 6 m.4.4 P r e p a r a t i o n a n d S u b m i ss io n o f P la n s

4.4.1 No person shall install or carry out any water-borne sanitaryinstallation or drainage installation or any works in connection with any-thing existing or new building or any other premises without obtainingthe previous sanction of the authority.4.4.2 Before the drainage work of any building is undertaken, adrainage plan drawn to a scale of not smaller than 1 : 200 shall be prepa-red and furnished along with the building plan. The plans shall showthe following:

a) Every floor of the building in which the pipes or drains are to beused;b) The position, forms, level and arrangement of the various partsof such building including the roof thereof;c) All new drains as proposed with their sizes and gradients;d) Invert levels of the proposed drains with corresponding groundlevels; ande) The position of every manhole, gully, soil and waste pipe, venti-lating pipe, rain-water pipe, water closet, urinal, latrine, bath,lavatory, sink, trap or other appliances in the premises proposedto be connected to any drains and the following colours arerecommended for indicating sewers, waste water pipes, rainwaterpipes and existing work:

ColouY

SewersWaste water pipes andrain-water pipesExisting work

RedBlue

Black14


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Provided that in the case of an alteration or addition to an exis-ting building this clause shall be deemed to be satisfied if theplans as furnished convey suff icient information for the proposalsto be readily identified with the previous sanctioned plans andprovided that the location of tanks and other fittings are consis-tent with the structural safety of the building.

4.4.3 In addition, a site plan of the premises on which the buildingis to be situated or any such work is to be carried out shall be prepareddrawn to a scale not smaller than 1 : 500.4.4.3.1 The site plan of the building premises shall show:4b)c34e>A

the adjoining plots and streets with their names;the position of the municipal sewer and the directions of flowin it;the invert level of the municipal sewer, the road level, and theconnection level of the proposed drain connecting the building inrelation to the sewer;the angle at which the drain from the building joins the sewer;andthe alignment, sizes, and gradients of all drains and also ofsurface drains; if any.separate site plan is not necessary if the necessary particulars tobe shown on such a site plan are already shown in the details plan.

4.4.4 In respect of open drains, cross-sectional detail shall be preparedto a scale not smaller than 1 : 50 showing the ground and invert levels,level of outfall and any arrangement already existing or proposed for theinclusion of any or exclusion of all storm water from the sewers.4.4.5 The plans for the building drainage shall in every case beaccompanied by specifications for the various items of work involved.

4.5 E s t i ma t i o n o f M a x imu m F l o w o f D o me s t i c S e w a g e4.5.1 The maximum flow in a building drain or a stack depends on theprobable maximum number of simultaneously discharging appliances. Forthe calculation of this peak flow certain loading factors have been assig-ned to appliances in terms of fixture units,and frequency of use. considering their probabilityThese fixture unit values are given in Table 1.

4.5.1.1 For any fixtures not covered under Table 1, Table 2 may bereferred to for deciding their fixture unit rating depending on their drainor trap size.15


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TABLE 1 FIXTURE UNITS Fgg;RzENT SANITARY APPLIANCE( ckruss4.5.1 )

TYPE. or FIXTVFGOne bath room group consisting of water closet, wash basin

and bath tub or shower stall:a) Tank water closetb) Flush-valve water closet

Bath tub*BidetCombination sink-and-tray ( drain board )Drinking fountainFloor trapstKitchen sink, domesticWash basin, ordinaryfWash basin, surgeonsShower stall, domesticShowers ( group ) per headUrinal wall lipUrinal stallWater closet, tank-operatedWater closet, valve-operated

FIXTURE UNIT VALUEAS LOAD FACTORS

6a3334121223444a

*A shower head over a bath tub does not increase the fixture value.tSize of floor trap shall be determined by the area of surface water to be drained.XWash basins with 32 mm and 40 mm trap have the same load value.TABLE 2 FIXTURE UNIT VALUES FOR FIXTURES BASED ONFIXTURE DRAIN OR TRAP SIZE

( CImua 4.5.1.1 )FIXTURE DRAIN OR TRAP &BE FIXTURE NITVALUE

( m m )3 0 a n d s m a l l e r 140 250 365 475 5

100 64.5.1.2 F r o m T a b l es 1 a n d 2, tk t o t a l l oa d o n a n y p i p e i n t e r m s o ffi xt u r e u n i t s m a y b e c a lc u la t e d k n o w i n g t h e n u m b e r a n d t y p e of a p p l ia n c e sc o n n e c t e d t o t h i s p i p e .

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CSl.3 For convertin4 t h e total load in fixture units to the peak flowin Iitres per minute, Fig. 1 M to be used.

1A Estimate Curves

FIXlURE UNITS- For system predominantly for flush valves___---_- For system predominantly for flush tanks

1B Enlarged Scale CurvesFrc. 1 PEAK FLOW LOAD CURVES4.5.1.4 The maximum load in fixture units permissible on variousrecommended pipe sizes in the drainage system are given in Tables 3and 4.4.5.1.5 Results should be checked to see that the soil, waste andbuilding sewer pipes are not reduced in diameter in the direction of flow.Where appliances are to be added in fixture unit, these should be takeninto account in assessing the pipe sizes by using the fixture units givenin Tables 1 and 2.

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TABLE 3 MAXIMUM NUMBE R OF FIXTURE UNITS THAT CAN BECONNECTED TO BRANCHES AND STACKS( Cha su 4.5. I .4 )

DI~TEB or M~xrBua r NUYBEB OB FIXTURE UNI TS* THAT BAY BE CONNECTED TOPIPE r------- _--- A______________~mm Any Horizon- One Sta ck of More Than 3 Storeys in Heighttal Fixture 3 Storeys in C----- - -4-_____~Bran&t Height or 3 Total for Total at oneInt ervals stack storey on bra nchinterval(1) (2) (3) (4) (5)30 1 2 2 140 3 4 8 250 6 10 24 665 12 20 42 975 20 30 60 16

100 160 240 500 90125 360 540 1 100 200150 620 960 1 900 350200 1400 2 200 3600 600250 . 2 500 3800 5 600 1 000300 3 900 6000 8400 1500375 7 000 - -

*Depending up on th e probability of simulta neous use of appliances considerin g th efrequency of use an d peak discha rge ra te.iDoes not include bran ches of th e building sewer.

TABLE 4 MAXIMUM NUMBE R OF FIXTURE UNITS THAT CAN BECONNECTED TO BUILDING DRAINS AND SEWERS( CImrsc4.5.1.4 )

DIAMETER GRADIENTOr PIPE ~~~~_~~_~~~~~~ _--h-_-__--__-_____-~mm l/200 l/100 l/50 l/25100 - 180 216 250150 - 700 840 1 000200 1 400 1 600 1 920 2 300250 2 500 2 900 3 500 4200300 3 900 4 600 5 600 6 700375 7 000 8 300 10 000 12 000

NOTE 1 - Maximum nu mber of fixtur e units that may be connected to anyportion ( see Note 2 ) of th e building dra in or the building sewer is given.NOTE 2 - Includes bran ches of th e building sewer.


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IS t 1742 - 19834.6 Gradients and Pipe Sizes

4.6.1 Gradients4.6.1.1 The discharge of water through a domestie drain is inter-

mittent and limited in quantity and, therefore, small accumulations of solidmatter are liable to form in the drains between the building and thepublic sewer. There is usually a gradual shifting of these deposits asdischarges take place. Gradients shall be sufficient to prevent thesetemporary building up and blocking the drains.4.6.1.2 Normaliy, the sewer shall be designed for discharging threetimes the dry-weather flow flowing half-full with a minimum self-cleansingvelocity of 0.75 m/s. The approximate gradients which give this velocityfor the sizes of pipes likely to be used in building drainage and the corres-ponding discharges when flowing half-full are as follows:

Diameter Gradients Dischargemm ms/min100 1 in 57 0.18150 1 in 100 0.42200 1 in 145 0.73230 1 in 175 0.93250 1 in 195 1.103co 1 in250 l.iO

4.6.1.3 In cases, where it is practically not possible to conform tothe ruling gradients, a flatter gradient may be used but the minimumvelocity in such cases shall on no account be less than 0.61 m/s.

NOTE - Where gradients are restricted, the practice of using pipes of largerdiameter than is required by the normal flow in order to justify laying at a flattergradient does not result in increasing the velocity of flow but reduces the depth offlow and for this reason is to be deprecated.4.6.1.4 On the other hand, it is undesirable to employ gradientsgiving a velocity of flow greater than 2.4 m/s. Where it is unavoidable,cast-iron pipes shall be used. The approximate gradients which give avelocity of 2.4 m/s for the various sizes of pipes and the correspondingdischarge when flowing half-full are as follows:

Diameter Gradient Dischargemm ms/min100 1 in 5.6 0.59150 1 in 9.7 1.32200 1 in 14 2.4230 1 in 17 2.98250 I in 19 3.60300 1 in 24.5 5.30

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IS: 1742-19834.6.1.5 The discharge values corresponding to nominal diameter andgradient given in 4.6.1.2 and 4.6.1.4 are based on Mannings formula( n = 0.015 ).

4.6.2 P;Pe S izes - Subject to the minimum size of 100 mm the sizes ofpipes shall be decided in relation to the estimated quantity of f low andthe available gradient.4.7 Choice of Materials

4.7.1 S alt Glazed S toneware Pies - For all sewers and drains in all solids,except where supports are required as in made-up ground, glazed stone-ware pipe shall be used as far as possible in preference to other type ofpipes, they are particularly suitable where acid effluents or acid subsoilconditions are likely to be encounterd. Salt glazed stoneware pipes shallconform to IS : 651-1980* or IS : 30C6-1979t.4.7.2 Cement Concrete Pipes - When properly ventilated, cement concretepipes with spigot and socket or collar joints present as alternative toglazed ware sewers over 150 mm diameter. These shall not be used tocarry acid effluents or sewage under condition favourable for the produc-tion of hydrogen sulphide and shall not be laid in those subsoils which arel;kely to affect adversely the quality or strength of concrete. Cementconcrete pipes may be used for surface water drains in all diameters.These pipes shall conform to IS : 45&1971$. Where so desired the life ofcement concrete pipe may be increased by lining inside of the pipe bysuitable coatings like epoxy/polyester resin, etc.4.7.3 Cast Iron Pipes - Cast iron pipes ( see IS : 1536-19769 and +S :1537-19767 ) shall b e used in the following situations:

a) In bad or unstable ground where soil movement is expected;b) In made-up or tipped ground;c) To provide for increased strength where a sewer is laid at insuffi-cient depth, where it is exposed or where it has to be carried onpiers or above ground;d) Under buildings and where pipes are suspended in basements andlike situations;e) In reaches where the velocity is more than 2.4 m/set; andf) For crossings of water courses.-- *S pecification for salt-glazed stoneware pipes and fittings (fourth rmision ).tspecification for chemically resistant glazed stoneware pipes and fittings (ji rstrevision tfspecification for concrete pipes ( with and without reinforcements ) ( sccnnd rcuikm).$Specifi cation for centrifugally cast ( spun ) iron pressllre pipes for water, gas andsewage ( second reuision .aSpecif ication for vertically cast iron presstIre pipes for water, gas and sewage (first.evision).

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Is:174!2-f98!3473.1 It hU be noted that cast iron pipes even when given asprotective aintsR are liable to severe external cdrrosion in certain soils.Among sue soils are:a) soils permeated by py waters; andb) soils in which the subsoil contains appreciable concentrationsof sulphates. Local experiences shall be ascertained before castiron pipes are used where corrosive soil conditions are suspected.Where SO used, suitable measures for the protection of the pipesmay be restpred to as an adequate safeguard.

4.7.4 Asbestos Cement Pijes - Asbestos cement pipes are commonly usedfor house drainage systems and they shall conform to the requirementsspecified in IS: 1626 (Part 1 )-1980*. They are not recommended forunderground situations. However, asbestos cement pressure pipes conrormingto the requirements specified in IS : 1592-1980t may be used in undergroundsituations also, provided they are not subjected to heavy superimposedloads. These shall not be used to carry acid effluents or sewage underconditions favourable for the production of hydrogen sulphide and shall notbe laid in those subsoils which are likely to effect adversely the quality orstrength of asbestos cement pipes. Where so desired, the life -of asbestoscement pipes may be increased by lining inside of the pipe by suitablecoatings like epoxy/polyester resins, etc.

4.7.5 Lead Pipes - Branch soil Fipes from fittings to main soil pipes andbranch waste pipes from fittings to main stack and branch anti-siphonagepipes may be of lead and shall conform to IS : 404 ( Part I )-1977f.4.7.6 PVC Pipes - Unplasticized PVC pipes may be used for drainagepurposes; however where hot water discharge is anticipated, the wallthickness should be at least 3 mm irrespective of the size and flow load.UPVC pipe shall conform to IS : 4985-1981.

NOTE - Where possihlr>, high density polyethylene pipes ( HDPE ) and UPVCpipes may be used for drainage and sanitation purposes, depending upon suitabili ty.HDPE pipes shall conform to IS : 4984-197811.4.8 D r a i n a g e P i p e s - Drainage pipes shall be kept clear of all otherservices. Provisions shall be made during the construction of the buildingfor the entry of the drainage pipes. In most cases this may be doneconveniently by building sleeves or conduit pipes into or under the structurein appropriate positions. Th is will facilitate the installation and mainte-nance of the services.

*Specification for asbestos cement building pipes and pipe fittings, gutters andgutter fittings and roofing fittings: Part 1 Pipes and pipe f ittings (,firsf revision ).tspecif ication for asbestos cement pressure pipe ( second mi sion ).SSpecification for Lead pipes: Part 1 for other than chemical purposes ( secondrrvision ) .$Spe&fication for unplasticized PVC pipes for potable water supplies (first revision ).IlSpecificationfor high density polythylene pipes for potable water,supplies sewageand industrial effluents ( secondrevision ).21


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i&:1742-19834.8.1 Where soil and ventilating pipeti tit a&ommodated in duck,

access to cleaning eyes shall be provided. Any connection to a drain shallbe through a gully with sealed cover to guard against ingress of sewergas, vermin or backflow. Trenches and subway shall be ventilated,preferably to the open air.

4.8.2 All vertical soil, waste ventilating and anti-siphonage pipes shallbe covered on top with a copper or heavily galvanized iron wire dome OTcast iron terminal guards. All cast iron pipes which are to be paintedperiodically shall be fixed suitably to the wall to give a minimum clearanceof 50 mm.

NOTE - Asbestos cement cowls may be used in case asbestos cement pipes areused as soil pipes.4.83 Drainage pipes shall be carried to a height above the buildings asspecified for ventilating pipe ( see IS : 5329-1983* ).

4.9 Manholes - At every change of alignment, gradient or diameter ofa drain, there shall be a manhole or inspection chamber. Bends andjunctions in the drains shall be grouped together in manholes as far aspossible. The spacing of manhole pipe may be in accordance with IS :4111 ( Part 1 )-1967t.4.9.1 Where the diameter of the drain is increased, the crown of thepipe shall be fixed at the same level and necessary slope given in the invert

of the manhole chamber. In exceptional cases and where unavoidable, thecrown of the branch sewer may be fixed at a lower level but in such casesthe peak flow level of the two sewers should be kept the same.4.9.2 Chambers shall be of such size as will allow necessary examinationor clearance of drains. The sizes of manholes shall be adjusted to take intoaccount any increase in the number of entries to the manhole. Theminimum internal sizes of chambers ( between faces of masonary ) shall beas follows:

a) For depths of 1 m or lessb) For depths between 1 m and 1.5 mc ) For depths more than 1.5 m

O-8 x O-8 m1.2 x O-9 mCircular chambers with aminimum diameter of 1.4 mor rectangular chamberswith minimum internaldimensions of 1.2 x 0.9 mare recommended.

*Code of practice for sanitary pipe work above ground for buildings (Jirsf revision.$&cle of practice for ancillary structures in sewerage system: Par t 1 Manholes. _


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rs:r74!2-1983NOTE l- In adopting the above sizes of chambers, it should be ensured thatthese sizes accord with full or half bricks with standar d thickness of mortar joints soas to avoid wasteful cutting of brick .NATE 2 - The sizes of the chamber s may be adjusted to suit the availability oflocal building materials and economies of construction.

4.9.3 The access shaft shall be corbelled inwards on three sides at thetop to reduce its size to that of the cover frame to be fitted or alternativelythe access shaft shall be covered over by a reinforced concrete slab ofsuitable dimensions with an opening for manhole cover, and frame.4.9.4 The manhole shall be built on a base of concrete of a thickness ofat least 150 mm for manholes up to 1 m depth, at least 200 mm for man-holes from 1 to 2 m in depth and at least 300 mm for manholes of greaterdepth unless the structural design demands higher thickness.4.9.5 Thet hickness of walls shall not be less than 200 mm (.or one brick )

up to l-5 m in depth and 300 mm ( or one and a halF brick ) for depthsgreater than 1.5 m. The actual thickness in any case shah be calculatedon the basis of engineering design. Typical sections of the manholes areillustrated in Fig. 2, 3 and 4.4.9.6 Drop Manholes - Where it is uneconomic or impracticable toarrange the connection with 600 mm height above the invert of the man-hole, the connection shall be made by constructing a vertical shaft outsidethe manhole chamber as shown in Fig. 5. If the difference in level betweenthe incoming drain and the sewer does not exceed 600 mm and there issuff icient room in the manhole, the connecting pipe may be directlybrought through the manhole wall and the fall accommodated byconstructing a ramp m the benching of the manhole.4.9.7 Channels - These shall be semi-circular in the bottom half and ofdiameter equal to that of the sewer. Above the horizontal diameter, thesides shall be extended vertically to the same level as the crown of the out-going pipe and the top edge shall be suitably rounded off. The branchchannel shall also be similarly constructed with respect to the benching butat their junction with the main channel an appropriate fall suitably roundedoff in the direction of flow in the main channel shall be given.4.9.8 Rungs shall be provided in all manholes over O-8 m in depth andshall be of cast iron conforming to IS : 5455-1-969*. These rungs may be set

staggered in two vertical runs which may be 380 mm apart horizontally.The top rung shall be 450 mm below the manhole cover and the lowest notmore than 300 mm above the benching. The size of manhole cover shallbe such that,there shall be a clear opening of at least 500 mm in diameterfor manholes exceeding 0.9 m in depth. Circular cover are considereddesirable. Manhole covers and frames shall conform to the requirementsgiven in IS : 1726-1967t.*Specification for cast iron steps for manholes.tspecification for cast iron manhole covers and frames,

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IS t 1742 1989

RENDERING WITHCEMENT MORTAR I:2rSLOPE J IN 6

DETAIL OF BENCHING

SECTION XX SECTION YY

NOTE - Wal l th ickn esse sh a v e been inalcated in brick lengths to provide for useof modular bricks [ see IS : 1077-1966 Specification for common burnt clay buildingbricks (first revision ). ] or traditional bricks.15 B = one and a half brick length, etc. In the figure, B = one brick length,

FOG. 2 DETAILS OF MANHOLE ( DEP THS 1 m AND BELO W )


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IS: 1742-1983

i*_-__ ____________JI---SECTIONAL PLAN AT ZZ.-_CIOcmi-

SECTION XX

RENDERING WITHCEMENT MORTAR I:2SLOPE I IN 6

IDETAIL OF BENCHING

SECTION YYNOTE Wall thicknesses have been indicated in brick lengths to provide for use

of modular bricks [ see IS : 1077- 1966 Specif ication for common burnt clay buildingbricks (Jirst revision ) ] or traditional bricks. In the figure, B = one brick length,15 B = one and a half brick length, etc.

FIG. 3 DETAILSOF MANHOLE ( DEPTHSBETWEEN1 AND l-5 m )

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its:1742-1983

I-YSECTIONAL PLAN AT ZZ

SECTION XX

RENDERING WITHCEMENT MORTAR 1:2

DETAIL OF BENCHING

SECTION YY

NOTE Wall thicknesses have been indicated in brick lengths to provide for useof modular bricks [ SCL S : 1077-1966 Specification for common burnt clay buildingbricks (prst w&ion ) ] or traditional bricks.1.5 B = on; and a half brick length, etc.

In the figure, B = one brick length,

F1c.4 DETAILS OE MANHOLE (DEPTHS l-5 m AND ABOVE)

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L ______ ________ _______ Jt - YSECTIONAL PLAN AT ZZ

SECTION XX ECTION YY NOTE - Wall thicknesses have been indicated in brick lengths to provide for useof modular bricks [ JCL S : 1077-1966 Specif ication for common burnt clay buildingbricka (jrst revision ] o r traditional bricks. In the figure, B = one brick length,15 B = one and a half brick length, etc.

FIG. 5 DROP MANHO LE27


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i$ I 1942 19834.9.8.1 All manholes shall be constructed so as to be watertight undertest. No manhole or inspection chamber shall be permitted inside a build-ing or in any passage therein. Ventilating covers &all not be used for

domestic drains.4.9.9 All brick work in manhole chamber and shaft shall be carefullybuilt in English bond. The jointing face of each brick being well butteredwith cement mortar before laying, so as to ensure a full joint. Theconstruction of walls in brick work shall be done in accordance withIS : 2212-1962*. The.cement mortar used shall not be weaker than 1 partof cement to 3 parts of sand ( sue IS : 2250-1981t ).4.9.10 The wall shall be plastered ( 15 mm, Ma ) both inside and out-side with cement mortar 1 : 3; where sub-soil water conditions exist, a

richer mix may be used for both masonry and plaster. All angles shall berounded to 7.5 cm radius and all rendered internal surfaces shall have hardimpervious finish obtained by using a steel trowel.4.9.11 The channel or drain at the bottom of the chamber shall beplastered with cement mortar of 1 : 2 proportion and finished smooth, tothe grade ( where required ). The benching at the side shall be carriedout in such a manner as to provide no lodgement for any splashings in caseof accidental flooding of the chamber.

4.10 S t o r m Wa t e r D r a i n a g e - The object of the storm water drainageis to collect and carry, for suitable disposal, the rain water collected withinthe premises of the building.

4.10.1 W ater Precipitat ion and Run-of--. Rainfall statistics for the areasunder consideration shall be studied to arrive at a suitable figure on thebasis of whic.h the storm water drains could be designed. Considerationshall be given to the effects of special local conditions and to the intensityand duration of rainfall.4.10.2 Permeabilityof Suz face - The impermeability factor, that is, theproportion of the total rainfall discharging to a surface water drain afterallowing for soakage, evaporation and other losses, varies with thefrequency and duration of rainfall. These factors shall be taken intoaccount in design.

4.10.2.1 The whole of the rainfall on impervious areas shall beassumed to reach the drains, no allowance for evaporation or time ofconcentration being made in domestic drainage work. The roof area shallbe taken as the horizontal projection of the area.*Code of practice for brickwork.*Code of practice fol preparation and use of masonry mortars (@t revision ).

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IS : 1742 - 19834.10.3 ain Water Pipes for Drainnge of Roofs

4.10.3.1he roofs of a building shall be so constructed or framed asto permit effectual drainage of the rain water therefrom by means of asufficient number of rain-water pipes of adequate size so arranged, jointedand ftxed as to ensure that the rain-water is carried away from the buildingwithout causing dampness in any part of the walls or foundations of thebuilding or those of an adjacent building.

4.10.3.2 The rain-water pipes shall be 6xed to the outside of theexternal walls of the building or in recesses or chases cut or frame in suchexternal wall or in such other manner as may be approved by theauthority.4.10.3.3 A rain-water pipe conveying rain water shall discharge

directly or by means of a channel into or over an inlet to a surface drain orshall discharge freely in a compound, drained to surface drain but in nocase shall it discharge directly into any closed drain.4.10.3.4 Whenever it is not possible to discharge a rain-water pipeinto or over an inlet to a surface drain or in a compound, drained to asurface drain or in a street drain within 30 m from the boundary of thepremises, such rain-water pipe shall discharge into a gully trap which shallbe connected with the street drain; such a gully trap shall have a screenand a silt catcher incorporated in its design.4.X0.3.5 If such street drain is not available within 30 m of theboundary of the premises, a rain-water pipe may discharge directly intothe kerb drain and shall be taken through a pipe outlet across the foothpathif any, without obstructing the path.4.10.3.6 A rain-water pipe shall not discharge into or connect withany soil pipe or its ventilating pipe or any waste pipe or its ventilating pipenor shall it discharge into a sewer unless specifically permitted to do so bythe authority in which case such discharge into a sewer shall be interceptedby means of gully trap.4.10.3.7 Rain-water pipes shall be constructed of cast iron. asbestoscement, galvanized sheet or other equally suitable material and shall besecurely fixed.4.10.3.8 Rain-water pipes shall be normally sized on the basis ofroof areas according to Table 5. A bell mouth inlet at the roof snrface isfound to give better drainage effect provided proper slopes are given tothe roof surface. The spacing of pipes depends on the position of thewindows and arch openings but 6 m apart is a convenient distance. Thestrainer area shall be I+ to 2 times the area of pipe to which it connects,

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fS:1742- 19834.10.3.9 The storm water shall be led off in a suitable open drain toa water course. The open drain, if not of pucca masonry throughout,shall be constructed in pucca masonry as at least where there is either achange in direction or gradient.TABLE 5 S IZI NG OF RAIN-WATER PI PES FOR ROO F DRAINAGE

SL DIA opNo. Avmsn on RATE OF RAINFALL N mm/hPIpa ~------~--_---h-------~~~-~mm 50 75 100 125 150 200Roof Area, Squar e Metr esi) 50 13,4 8.9 6.6 5.3 44 3.3

ii) 65 241 16.0 12.0 9.6 8-O 60iii) 75 4x3 27.0 204 16.3 13.6 102iv) 100 85.4 57.0 42.7 34.2 28.5 21.3v) 125 - - 805 64.3 53.5 40.0

vi) 150 - - - - 83.6 62.7

4.10.4 Size and Gradients of Pik es - The pipes shall be so designed asto give a velocity of flow of not less than 1 m/s when running half-full.The maximum velocity shall not exceed 2.5 m/s.4.10.5 Disposal - Sur face water may be disposed of in one or moreways specified in 4.10.5.1 to 4.10.5.5 but preferably by the method given

in 4.10.5.1.4.10.5.1 Separate system - All courtyards shall be provided with oneor more outlets through which rain-water shall be diverted into the stormwater drains and away from any opening connecting with any sewer.Where storm water drains are necessary for the discharge of rain-water to a public storm water drain, such drains shalt be designed for theintensity of rain based on local conditions but in no case they shall bedesigned for intensity of rainfall of less than 13 mm/h. Usually, eachseparate plot shall have a separate drain connection made to a covered or

open public drain. Such connection to a covered drain shall be madethrough a pipe at least 3.5 m in length, laid at a gradient of not less thanthat of the connecting drain. The storm water from the plot shoulddischarge into the storm water drain directly and not through a trap.4.10.5.2 Combined OY partial& separate sy stem - Where levels do notpermit connection to a public storm water drain, storm water fromcourtyard may be connected to the public sewer provided it is designed toconvey combined discharge. In such cases, the surface water shall beadmitted to the soil sewer through trapped gullies in order to prevent theescape of sewer air.

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I$ : 1742 - 19834.10.5.3 To a w ater course - It may often be convenient to dischargesurface water to a nearby stream or a water course. The invert Lvel of theout-fall shall be about the same as the normal water level in the watercourse. The out-fall shall be protected against floating debris by a screen.4.10.5.4 70 storage tank s - Water from the roof of a building maybe led straight from the down pipes to one or more watertight storagetanks. Such storage tanks shall be raised to a convenient height aboveground and shall always be provided with ventilating covers, and havedraw-off taps suitably placed so that the rain water may be drawn off fordomestic washing purposes or for garden water. A large imperviousstorage tank is sometimes constructed underground, from which rain wateris pumped as required to the house. All storage tanks shall be providedwith an overflow.4.10.5.5 An arrangement shall be provided in an ram-water leaderto divert the first washings from the roof or terrace catchment as theywould contain much undesirable material. The mouth of all pipes andopenings shall be covered with mosquito-insect proof wire net.4.10.5.6 French drains may be employed as surface water drains andare useful in the drainage of unpaved surface, such as playfields andcertain types of roads. When used for this purpose in addition to thedrainage being filled with rubble, it 1s &en advisable to include a fielddrain in the trench bottom.

4.11 Subsoil W a t e r D r a i n a g e4.11.1 General - Subsoil water is that portion of the rainfall which isabsorbed into the ground and the drainage of subsoil water may benecessary for the following reasons:

a) To increase the stability of the surface;b) To avoid surface flooding;c) To alleviate or to avoid causing dampness in the building,especially in the cellars;d) To reduce the humidity in the immediate vicinity of the building;

ande) To increase the workability of soil.4.11.2 Deph of W ater Table - The standing level of the subsoil waterwill vary with the season, the amount of rainfall and the proximity andlevel of drainage channels. Information shall be obtained regarding thislevel by means of boreholes or trial pits preferably the latter. It i sdesirable though not always practicable to ascertain the level of thestanding water over a considerable period so as to enable the seasonalvariation to be recorded and in particular the high water level. The


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IS I 1142 - 1983direction of the flow of subsoil wat er ma y usu ally be judged by the generalinclination of the land surface, and the main lines of the subsoil drains shallf&x+ the natural falls wherever possible.

4.11.3 P7ecaution.f - Subsoil drains shall be sitted so as not to endangerthe stability of the buildings or earthwork. In some portions of the drain,it may be necessary to use non-porous jointed pipes.4.11.3.1 No field pipe shall be laid in such a manner or in such aposition as to communicate directly with any drain constructed or adaptedto be cased for conveying sewage except where absolutely unavoidable andin that case a suitable efficient trap shall be provided between subsoil drainand such sewer.

4.11.4 Systems OJSubsoil D7ainage4.11.4.1 Field drain @es - Clay or concrete porous pipes may beused and shall be laid in one of the following ways:4b)

4

Natural - The pipes are laid to follow the natural depressionsor valleys of the site, branches discharging into the main astributaries into a river.Harringbone - A system consisting of a number of main drainsinto which discharge, from both sides, smaller subsidiary branchesparallel to each other but at an angle to the mains forming aseries of herringbone patterns.Grid - A main or mains near the boundaries of a site into whichbranches discharge from one side only.

d) Fan shaped - The drains are laid converging to a single outletat one point on the boundary of a site, without use of main orcoilecting drains.e) Moat 07 cut-of system - Sometimes drams are laid on one or moresides of a building to intercept the flow of subsoil water and therebyprotect the foundations.4.11.4.2 The choice of one or more of these systems will naturallydepend on the local conditions of the site. For building sites the mainsshall be not less than 75 mm in diameter and the branches not less than65 mm in diameter but normal practice tends towards the use of 100 mmand 75 mm respectively. The pipes shall generally be laid at 600 to 900 mmdepth or to such a depth to which it is desirable to lower water table andthe gradients are determined rather by the fall of the land than by consi-derations of self-cleansing velocity. The connection of the subsidiary drainto main drain is best made by means of a clayware or concrete junctionpipe. The outlet of a subsoil system may discharge into a soakaway orthrough a catchpit into the nearest ditch or water course. Where these are

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fS : 1742 - 1983not available the subsoil drains may be connected, with the approval ofthe authority, through an intercepting trap to the surface water drainagesystem.

Nom - Care shall be taken that there i s no backilow from subsurface drainsduring heavy rains.5. CONSTRUCTIONS RELATING TO CONVEYANCE OFSANITARY WASTES5.1 P i p e L in e s a n d J o in t i n g - All soil pipes, waste pipes, ventilatingpipes and all other pipes, when above ground, shall be gas-tight. All sewersand drains laid below ground shall be watertight.5.2 J o in t i n g L e a d a n d I r o n P i p e s - Where any lead waste pipe, ventil-ating pipe or trap is connected with an iron pipe or drain communicatingwith a sewer these shall be inserted between such lead waste pipe and suchiron pipe or drain an ordinary thimble of copper or brass, which shall beconnected to such lead waste pipe by means of a wiped joint. The thimbleshall be connected with such cast iron pipe by means of a joint ( see Fig. 6 )made with molten lead, properly caulked, a sufficient quantity of lead beingmelted at a time to finish each joint at one pouring.

/

LEAD PIPE

f-WIPEDSOLDERJOINT

BRASS ORCOPPER/ THIMBLE

MOLTEN LEJOINT WELLCAULKEDYARN

Cl PIPE

AD

FIG. 6 J OINTING LEAD P IP E TO CAST-IRONP I P E

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IS:1742 -19835 .3 J o i n t i n g S t o n e w a r e w i t h Le a d P i p e s - Where any stoneware orsemi-vitrified ware trap or pipe is connected with a lead soil pipe, wastepipe or trap communicating ith a sewer, these shall be inserted betweensuch stoneware or semi-Gtrifie ware trap or pipe and such lead soil pipe,waste pipe, or trap a socket of copper, cast brass or other suitable alloy,which shall be connected with such stoneware or semi-vitrified ware trapor pipe by means of a joint made with mortar consisting of one part ofcement and one part of coarse sand with the.lead soil- pipe, waste pipe ortrap by means of wiped metallic joint ( see Fig. 7 ).

/-WC TRAP,CEMENT MORTARJOINT(l:l)

-YARN

-BRASS THiMBLEWITH SOCKET

\WIPED SOLDERJOINT

LEAD PIPE

FIQ. 7 J OINTING STONEWAREOR SEMI-VITRI FI EDWARE P IP Z ORTRAP TO LEAD PIP E

5 .4 J o i n t i n g C a s t I ro n P i p e s w i t h S t o n e w a re P i p e s ( s e e F i g . 8 ) -Where any cast iron soil pipe, waste pipe, ventilating pipe or trap is con-nected with a stoneware or semi-vitrified waste pipe or drain communicat-ing with a sewer, the beaded spigot end of such cast iron soil pipe, wastepipe, ventilating pipe, or trap shall be inserted into a socket of such stone-ware of semi-vitrified ware pipe or drain and the joint made with mortarconsisting of one part of cement and one part of clean coarse sand afterplacing a tarred gasket or hemp yarn soaked in neat cement slurry roundthe joint and inserted in it by means of a caulking tool.34


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1s : 1742 - 1983

III /-SW PIPEFIG 8 JOINTING C I PIPE TO STONEWAREPIPE

5.4.1 Jointing Stoneware with Cast Iron Pipes - Where any water closetpan or earthenware trap connected to such pan is to be jointed with acast iron soil pipe, the joint between the stoneware spigot and the cast ironsocket shall always be of a flexible ( non-rigid ) nature. Such joint shall bemade preferably with a mixture of bitumen and chopped asbestos fibre( not dust ).5.5 J o in t i n g L e a d P i p e s - The joints in lead pipes shall be made aswiped solder joints ( see Fig. 9 ). The minimum and the maximum lengthof the wiped solder joints shall be 80 mm and 90 mm respectively. Thesolders shall generally consist of two parts of lead and one part of tin.5.6 J o i n t i n g G la z e d S t o n e w a r e P i p e s ( s e e F i g . 1 0 ) - Tarred gasketor hemp yarn soaked in thick cement slurry shall first be placed round thespigot of each pipe and the spigot shall then be placed well home into thesocket of the pipe previously laid. The pipe shall then be adjusted andfixed in the correct position and the gasket caulked tightly home so as notto fill more than l/4 of the total depth ( or 13 mm in depth ) of the socket.

5.6.1 The remainder of the socket shall be filled with a stiff mixture ofcement mortar in the proportion of one part cement and one part sharpsand, When the socket is filled, a fillet shall be formed round the jointwith a trowel, forming an angle of 45 with the barrel of the pipe.35


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tS : 1742- 1983

WIPEDSOLDER

FIG. 9 JOINTING LEAD P IP E TO LEAD P IP E

CEMENT MORTAR TARRED GASKET ORSPUN YARN SOAKEDIN NEAT CEMENT

FIG . 10 TYP ICAL DET AILSOF CEME NT J OINTS FOR GLAZEDSTONEWARE PIPE S

5.6.2 Mort ar sha !l be mixed as wan ted for imm ediate use an d no morta rshall be beaten up and used before it has begun to set.

5.6.3 After th e joint is ma de, an y extra neous ma terial shall be rem ovedfrom the inside of th e joint with a suita ble scraper or badger . Thenewly made joints shall be protected, un til set, from th e sun , drying winds,ra in or frost. Sacking or other suita ble mat erials, which shall be kept.da mp,may be used for the purpose.

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I6 t 1742 - 19835.7 Jointing Concrete Pipes - Concrete pipes shall be jointed as des-cribed in IS : 7 83-1959*. The spigots and sockets shall be thoroughly wetbefore the joints are made.5.8 Jointing Cast Iron Pipes

5.8.1 Lead Run Joints ( Cart-Lead Joints ) - The spigot shall be centredin the adjoining socket by tightly caulking in sufficient turns of tarred gasketor hemp yarn to leave unfilled half the depth of socket for lead. Whengasket or hemp yarn has been caulked tightly home, a jointing ring shallbe placed round the barrel and against the faces of the socket. Moltenpig lead shall then be poured in to fill the remainder of the socket. Thelead shall then be solidly caulked with suitable tools and hammers of notless than 3 kg weight, right round the joint to make up for the shrinkageof the molten metal on cooling and shall be preferably finished 3 mmbehind the socket face. Lead for caulking shall conform to IS : 782-19781_.5.8.1.1 It is essential that the pipes be perfectly dry before lead runjoints are made, otherwise blow holes may occur in the lead and injurymay result to the pipe jointer. This method, therefore, requires specialcare in wet trenches.

5.8.2 Lead-Wool or Lead-Fibre Joints - These joints are suitable for wetconditions. Special attention is necessary in. caulking. The socket shall becaulked with tarred gasket or hemp yarn as described in 5.8.1 and the leadfibre inserted into the socket and tightly caulked home skein by skein withsuitable tools and hammers of not less than 2 kg weight, until the joint isfilled. Lead-wool used for caulking shall conform to IS : 782-1978t.

5.8.3 Cement Joints - The following procedure is recommended:a) The joint is first yarned with hemp yarn dipped in the cementslurry. The yarn is first inserted to slight depth and well pressedin the same manner as for lead jointing,b) Cement mortar of ratio 1 : 1 with a water cement ratio not exceed-ing one part of water to 5 parts of cement ( by weight ) should berammed into the joint by caulking tools,c) The filling to complete and caulked again,d) Joints should be kept wet for 24 h after making, ande) Use of lead joint at intervals is recommended.

5.8.4 Flanged Joints - If a drain be constructed of flanged pipes, thejoints shall be securely bolted together with a rubber or other suitableinsertion.

*Code of practice for laying of concrete pipes.tSpecification for caulking lead ( third reuision .37


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IS I 1742 - 1983 * .5 .9 C o n c re t e S u p p o r t o r P ro t e c t i o n fo r P i p e s - It may be necessaryto support or surround pipe sewers or drains by means of concrete incertain circumstances and any of the methods given in 5.9.1 to 5.9.7 maybe adopted.5.9.1 Bedding- Bedding ( see Fig. 11 ) shall be rectangular in sectionand shall extend laterally at least 150 mm beyond and on both sides of theprojection of the barrel of the pipe. The thickness of the concrete belowthe barrel of the pipe shall be not less than 100 mm for pipes under 150 mmdiameter and 150 mm for pipes 150 mm and over in diameter. Wherebedding is used alone, the concrete shall be brought up at least to theinvert level of the pipe to form a cradle and to avoid line contact betweenthe pipe and the bed.

5.9.24b)4

.W = D + 30 cm , where D is external diameter of, the pipeT = ( 10 cm for pipes under 150 mm nominal dla,I 15 cm for pipes of 150 mm nominal dii and over.

FIG. 11 BEDDINGHuunching - Concrete haunching ( see Fig. .12 ) shall consist ofiA concrete bed as described for bedding ( ste 5.9.1 ).The full width of the bed carried up to the level of the horizontaldiameter of the pipe; andSplays from this revel carried up on both sides of the pipe, fromthe full width of the bed to meeting the pipe barrel tangentially.

W = D + 30 cm, where D is external diameter ofthe pipeT = c 10 cm for pipes under 150 mm nominal dia. 15 cm for pipes of 150 mm nominal dia and over.I

Flo. 12 HAUNCHING38


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. tS : 1742 19835.9.3 Surround or Encasing - The surround or encasing. ( sei Fig. 13 )shall be similar to haunching up to the hoti_zo_ntal diameter of the pipeand the top portion over this shall be finished in a semi-circular form togive a uniform encasing for the top half of the pipe.

l-l 5cm4

l------w+W = D + 30 cm, where D ishe external diameter of the pipe.

Fro. 13 SURROUND OR ENCASING5.9.4 Piers for Cast Iron Pipes - Where supporting piers are specified forcast iron pipes, they shall be not less than 30 cm in length ( parallel to the

. axis of the pipe ) and at least equal in section to that described for haunch-ing in 5.9.2. Pipes shall be built just behind the pipe sockets, intermediatepiers being provided where necessary.5.9.5 Glazed W are Pipes - The minimum support or protection forglazed stoneware pipes shall be as follows:

a) When cover is less than 1 m below ground level and where pipesare unavoidably exposed above ground surface, the pipes shall becompletely encased or surrounded with concrete;

b) Where the pipes are laid on a soft soil with the maximum watertable lying at the invert of the pipe, the pipe sewer shall be beddedon concrete;c) Where the pipes have to be laid in a soft soil with the maximumwater table rising above the invert of the pipe, but below the topof the barrej, the pipe sewers shall be haunched;d) Where the maximum water table is likely to rise above the top ofthe barrel or wherever the pipe is laid in soft soil, the pipesewers shall be completely encased or surrounded with concrete;and

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1s: 1742A983 .. 0: e) Where the sewers are to be laid adj acent to growing trees, thepipe sew ers shall be encased or surrounded with-concrete to. avoiddamage to the pipes likely to be caused by the roots of the trees.5.9.6 Cast Iron Pipes - In normal ground; no concrete support or

protection to cast iron pipes need be provided. Where concrete haunchingsurrounds or piers are required, these shall be in accordance with thedetails given in 5.9.5.5.9.7 Support of Pipes in Unstable Ground - In certain subsoils, rise andfall of the subsoil water level may be the cause of considerable earthmovement. This and other conditions of unstable ground call foradditional support to the pipes in the form of piles or trestles or othersuitable means.

5.10 Excavation5.10.1 Turf, topsoil or other surface material shall be set aside, turfbeing carefully rolled and stacked for use in reinstatement.5.10.2 Excavated material shall be stacked suff iciently away from theedge of the trench and the size of the spoil bank shall not be allowed tobecome such as to endanger the stability of the excavation. Spoil maybe carried away and used for filling the trench behind the work.5.10.3 Excavation shall proceed to within about 75 mm of the finishedformation level. This final 75 mm being trimmed and removed as aseparate operation immediately prior to the laying of the pipes or their

foundations.5.10.4 The sides of the trench shall be properly propped, wherenecessary.5.10.5 The width of the trench at bottom between faces of sheetingshall be such as to provide not less than 200 mm clearance on either sideof the pipe.5.10.6 Where the subsoil is unstable, a foundation for the pipes shall beformed by piling and bridging, earth consolidation or other efficientmeans.5.10.7 Excavation in roads shall be so arranged, in agreement with theproper authority, as to cause the minimum obstruction to traffic. Themethod to be adopted shall depend on local circumstances.5.10.8 All suitable broken surface material and hard-core shall be seton one side for use in subsequent reinstatement.5.10.9 Adequate warning lights shall be placed at night to indicate ailobstructions in the Iughway. Red flags shall be displayed along thetrenches during day time.

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IS :1742 - 1983'.5.10.10 A sufficient ,nnm&r of-men shall be employed to guard th;work and attend td the lamps.5.10.11 Blasting may be necessary in hard rock. It shall only be

carried out undei thorough .and competent supervision and with thewritten permission of the appropriate authorities, taking .a11 precautionsconnected with blasting operations.5.10.12 All pipes, ducts, cables: mains or other services exposed ,in thetrench shall be effectively supported by timbers and/of chain or ropeslings.5.10.13 Excavations below water table shall be done after dewateringthe trenches.5.10.14 All drainage sumps shall be sunk clear of the work outside thetrench or at the sides of manholes. After the completion of the work, any

pipes or drains leading to such sumps or temporary subsoil drains underpermanent work shall be filled in properly with sand and consolidated.5.11 Concreting - The work shall generally be done according toIS : 456-1978*.5.12 Laying of Pipes - The pipes shall be laid with the sockets leadinguphill and shall rest on solid and even foundations fof the full length ofthe barrel. Socket holes shall be formed in the foundation sufficientlydeep, to allow sufficient space for the pipe jointer to work right round thepipes and as short as is practicable to accommodate the socket in properposition and allow the joint to be made.

5.12.1 Where pipes are not bedded on concrete, the trench floor shallbe left slightly high and carefully bottomed up as pipe laying proceeds sothat the pipe barrels rest on firm 2nd undisturbed ground. If the excava-tion has been carried too low, any packing done shall be in concrete.5.12.2 If the floor of the trench consists of rock or very hard groundthat cannot easily be excavated to a smooth surfaces the pipes shall belaid on a cradle of fine concrete floor or a floor of gravel and crushedstone overlaid with concrete or on a well-consolidated gravel and crushedstone bed only so as to ensure even bearing.5.12.3 Each separate pipe shall be individually set for line and for level

using one of the following methods:a) Where long lengths of sewer or drain are to be constructed intrench with glazed stoneware or concrete pipes, properly paintedsight-rails shall be fixed across the trench at a height, equal thelength of the boning rod to be used, above the required invertlevel of the drain or sewer at the point where the sight rail isfixed. There shall be minimum three sight-rails in position oneach length of sewer or drain under construction at a particulargradient.*Code of practice for plant and reinforced concrete ( third revision ).

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&t 1742 - 1983

b)

4

4

Properly out wooden or iron pegs shall be driven into thefloors of the trenches at intervals of at least one metre less thanthe length of the straight-edge which is to be used. With theaid of a boning rod, equal in length to the height of the sight-railabove the required invert level, each peg shall be driven until itstop is at the exact level required for the invert of the pipeline atthat point; this will have occurred when a true bone is obtainedover boning rod and sight-rails. The underside of a straight-edge resting on the tops of those pegs will give level and gradientof the invert.proceeds. The pegs shall be withdrawn as pipe laying

To obtain a true line along the grade, a sideline shall be usedstrung tautly at half-pipe level between iron pins fnmly drivenin the floor of the excavation for the manhole at each end of theproposed pipe line, and the pipes shall be laid in such a way thatthe sockets are fixed just free of this side line. For long lengthsof drain, the side line may require intermediate support. Thepractice of laying to a top line is not recommended.In the case of short lengths of branch drain where it is inconve- ,nient 10 fix sight-rails, pegs shall be driven in to the floor of thetrench and their tops boned in with the aid of three equal boningr-ods, one of which is used on the pegs to be driven and the othertwo held at the invert level of the pipes or f ittings to be connec-ted. A side line shall be used to obtain a true line in thehorizontal plane.In the case of cast iron pipes, it is impracticable to use a straight-edge and the invert of each pipe shall be fixed to a true bone over the sight-rails by means of a boning rod, which in suchcases shall be provided with a bottom shoe to rest on the invertof the pipe being laid.Where it is necessary to cut pipes, this shall be done with asuitable wheel type pipe cutter so as to leave a clean and squareto the axis of the pipe.

5.13 Connection to an Existing Sewer - The connection to an exist-ing sewer shall, as far as possible, be done at the manholes. Where it isunavoidable to make connection in between two manholes, the work ofbreaking into the existing sewer and forming the connection shall becarried out by the authority or under its supervision.Breaking into the sewer shall be effected by the cautious enlarge-ment of a small hole and every precaution shall be taken to prevent anymaterial f rom entering the sewer. No connection shall be formed in sucha way as to constitute a projection into the sewer or to cause any diminu-tions in its effective size.

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5.14 Back-Filling5.14.1 Filling of the trench shall not be commenced until the length ofpipes therein has been tested and passed ( see 8.2 ).5.14.2 All timber which may be withdrawn with safety shall be removedas filling proceeds.5.14.3 Where the pipes are unprotected by concrete haunching, thefirst operation in filling shall be carefully done to hand-pack and tempselected fine material around the lower half of the pipes so as to buttressthem to the sides of the trench.5.14.4 The filling shall then be continued to 150 mm over the top ofthe pipe using selected fine hand-packed material, watered and rammedon both sides of the pipe with a wooden rammer. On no account shallmaterial be tipped into the trench until the first 150 mm of fill ing has beencompleted. The process of filling and tamping shall proceed evenly so asto maintain an equal pressure on both sides of the pipeline.5.14.5 Filling shall continue in layers not exceeding 150 mm in thickness, each layer being watered and rammed.5.14.6 In roads, surface materials previously excavated shall be replaced as the top layer of the filling, consolidated and maintained satisfactorilytill the permanent reinstatement of the surface is made by the authority.5.14.7 In gardens, the topsoil and turf, if any, shall be carefullyreplaced.

6. CONSTR UCTIO N RELATING TO CONVEYANCE OF RAIN ORSTORM WATER6.1 Roof Gutters - Roof gutters, shall be of galvanized iron sheets notless than l-25 mm in thickness and shall conform to IS : 277-1977*. Thegutter shall be semicircular in section with a width at top about twice thediameter of the down pipe. The gutters shall be fored 25 mm below theedge of the roof.

6.1.1 MS brackets 25 x 6 mm shall be used to support the gutter atabout 1.2 m intervals. A convenient method will be to fix the brackets toevery alternate after with three 50 mm screws.6.1.2 All junctions and joints shall be thoroughly water-tight-riveted,bolted or soldered. All joints between successive length of gutters shallhave an overlap of at least 50 mm. The drop in the overlap shall alwaysbe in the direction of the fall of the gutter. Ends of guttering shall be*Specification for galvanized steel sheets ( plain and corrugated ) ( third rstision ).

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IS : 1742 - 1983closed with galvanized sheets not less than 1.25 mm in thickness, to fit thesection and made water-tight. Junctions with down-fall rain-water pipesor leaders shall be made water-tight. Gutters shall have a generalminimum fall of 1 in 120.6.2 Rain-Water Pipes

6.2.1 -Cast Iron Pipes - Rain-water pipes or leaders if of cast iron shallbe with socketed joints having lugs cast on for fixing and shall conform tothe requirements specified in IS : 1230-1979*. The shoe may be fixed150 mm above ground level. Bends and offsets are to be avoided as far aspossible.42.2 Galvaniz ed Iron Pipes - Galvanized iron pipes shall conformto IS : 1239 ( Part I )-1979t. The work will be similar to cast iron pipes

except that they are fixed with straps or dogs one for each 2-m length ofpipe. Joints between successive lengths of pipes will be by collars at least10 cm deep riveted tightly and securely to the pipes, and the straps ordqgs be riveted or bolted through this collar by 9.5 mm galvanized ironbolts.6.2.3 Asbestos Cement Pipes - Rain-water pipes and gutters shall conform ,,to IS : 1626 (Part 1 )-1980$. Only the pipes will be fixed with strapsor clips.

6.2.3.1 All rain-water leaders from roofs or terraces shall be screenedoff by gratings at the top to prevent leaves, rodents, etc, entering thepipes.

6.2.3.2 The laying of pipes underground and the construction ofchambers and manholes shall be carried out as in the case of sewers forfoul water.7. CONSTRUCTION RELATING TO CONVEYANCE OF SUBSOILWATER7.1 Subsoil Drains

7.1.1 Field Drain Pipes - Suitable pipes for this purpose are plaincylindrical glazed stoneware pipes, or concrete porous pipes though thelatter may prove unsuitable where subsoil water carries sulphates or isacidic owing to the presence of peat. Trenches for. these pipes need bejust wide enough at the bottom to permit laying the pipes, which shall belaid with open joints to proper lines and gradients.*Specification for cast iron rainwater pipes and fittings ( secondeuision .tSpecilication for mild steel tubes, tubulars and other wrought steel fittings: Part 1Mild steel tubes (&fh f#?hion ).ISpecification for asbestos cement building pipes and pipe fittings, gutters and gutterfittings and roof fittings: Part 1 Pipes and pipes fittings.

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IS 8 1742 - 19837.1.1.1 It is advisable to cover the pipes with clinker free from fineash, brick ballast or other suitable rubble, or a layer of inverted turf,brush-wood or straw before refilling the trench, in order to prevent theinfiltration of silt through the open joints. Where the subsoil drain is also

to serve the purpose of collecting surface water, the rubble shall be carriedup to a suitable level and when required for a lawn or playing field, theremainder of the trench shall be filled with previous topsoil. Whenrefilling the trenches, care shall be taken to prevent displacemet of pipesin line of levels. When they pass near trees or through hedges, socketpipes with cement or bitumen joints shall be used to prevent penetrationby roots.7.1.2 French Drains - A shallow trench is excavated, the bottom neatlytrimmed to the gradient and the trench filled with broken stone, gravel orclinker, coarse at the bottom and finer towards the top.

8. INSP ECTIO N AND TESTING8.1 Inspection

8.1.1 All sanitary appliances and fitments shall be carefully examinedfor defects before they are installed and also on completion of the work.8.1.2 Pipes are liable to damage in transit and, not withstanding teststhat may have been made before despatch, each pipe shall be carefullyexamined on arrival on the site. Preferably, each pipe shall be rung witha hammer or mallet and those that do not ring true and clear shall berejected. Sound pipes shall be ca

ibs standards

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