Planning Design Criteria

8/22/2019 Planning Design Criteria

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PLANNING DESIGN CRITERIA: WATER SUPPLY

All buildings shall conform to the general requirements

Rate of Flow

One of the important items that needs to be determined before the sizes

of pipes andfittings for any part of the water piping system may be

decided upon, is the rate of flow in the service pipe which, in turn

depends upon the number of hours for whichthe supply is available at

sufficiently high pressure. If the number of hours for whichthe supply is

available is less, there will be large number of fittings in

usesimultaneously and the rate of flow will be correspondingly large.

The data required for determining the size of the communication and

service pipes are:-the maximum rate of discharge required;-the length of the pipe; and- The head loss by friction in pipes, fittings and meters.Discharge

Computation The design of the consumers pipes or the supply pipe to

the fixtures is based on:the number and kind of fixtures installed;the fixture unit flow rate; andThe probable simultaneous use of these fixtures.


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The rates at which water is desirably drawn into different types of

fixtures are known. These rates become whole numbers of small size

when they are expressed in fixture unit. Probable simultaneous

demand The possibility that all water supply taps in any systemin domestic and commercial use will draw water at the same time is

extremely remote. Designing the water mains for the gross flow will

result in bigger and uneconomical pipe mains and is not necessary.

Pipe Size ComputationCommercially available standard sizes of pipes are only to be usedagainst the sizesarrived at by actual design. Basic Principles Wholesome

water supply provided for drinking and culinary purposes shall not be

liable to contamination from any less satisfactory water. There shall,

therefore, be no cross-connection whatsoever between the distribution

system for wholesome water and any pipe or fitting containing

unwholesome water, or water liable to contamination, or of uncertain

quality, or water which has been used for any other purpose. Theprovision of reflux or non-return valves or closed and sealed stop valves

shall not be construed as a permissible substitute for complete absence

of cross connection.The design of the pipe work shall be such that there is no possibility of

backflow towards the source of supply from any cistern or appliance,

whether by siphonage or otherwise. Reflux non-return valves shall not

be relied upon to prevent such backflow.


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Where a supply of less satisfactory water than wholesome water

becomesinevitable as an alternative or is required to be mixed with the

latter, it shall bedelivered only into a cistern and by a pipe or fitting

discharging into the air gapat a height above the top edge of the cisternequal to twice its nominal bore andin no case less than 150 mm. It is

necessary to maintain a definite air gap in allappliances or taps used

in water closets.All pipe work shall be so designed, laid or fixed and maintained as to

remaincompletely water-tight, thereby avoiding wastage, damage to

property and therisk of contamination.

No water supply line shall be laid or fixed so as to pass into or through

anysewer, scour outlet or drain or any manhole connected therewith

nor throughany ash pit or manure pit or any material of such nature

that is likely to causeundue deterioration of the pipe, except where it is

unavoidable.Where the laying of any pipe through corrosive soil or previous material

isunavoidable, the piping shall be properly protected from contact with

such soilor material by being carried through an exterior cast iron tube

or by some othersuitable means as approved by the Authority. Any

existing piping or fitting laidor fixed which does not comply with theabove requirements, shall be removedimmediately by the consumer and

re-laid by him in conformity with the aboverequirements and to the

satisfaction of the Authority.


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Where lines have to be laid in close proximity to electric cables or in

corrosive soils, adequate precautions/protection should be taken to avoid

corrosion.Underground piping shall be laid at such a depth that it is unlikely to be

damaged by frost or traffic loads and vibrations. It shall not be laid in

ground liable to subsidence, but where such ground cannot be avoided;

special precautions shall be taken to avoid damage to the piping. Where

piping has to

be laid across recently disturbed ground, the ground shall be thoroughly

consolidated so as to provide a continuous and even support.Undesigning and planning the layout of the pipe work,due attention shall be given to the maximum rate of discharge required,

economy in labour and materials, protection against damage and

corrosion, water hammer, protection from frost, if required, and to

avoidance of airlocks, noise transmission and unsightly arrangement.To reduce frictional losses, piping shall be as smooth as possible inside.Methods of jointing shall be such as to avoid internal roughness

and projection at the joints, whether of the jointing materials or

otherwise.


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Change in diameter and in direction shall preferably be gradual rather

than abrupt to avoid undue loss of head. No bend or curve in piping shall

be made which is likely to materially diminish or alter the cross-section.

No boilers for generating steam or closed boilers of any description or

any machinery shall be supplied direct from a service or supply pipe.

Every such boiler or machinery shall be supplied from a feed cistern.

PLANNING DESIGN CRITERIA: DRAINAGETo achieve this aim a drainage system shall satisfy the following

requirements:rapid and efficient removal of liquid wastes without leakage;

prevention of access of foul gases to the building and provision for their

escape from the system,adequate and easy access for clearing obstructions;

prevention of undue external or internal corrosion, or erosion of jointsandprotection of materials of construction; and


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Avoidance of air locks, siphonage, proneness to obstruction, deposit and

damage. The realization of an economical drainage system is added by

compact grouping of fitments in both horizontal and vertical directions.

This implies that if care is taken and ingenuity brought into playwhen designing the original building or buildings to bedrained, it is

possible to group the sanitary fittings and other equipment requiring

drainage; both in vertical and horizontal planes, as to simplify the

drainage system and make it most economical. Efficient and an

economical plumbing system can be achieved by planning the toilets in

compact grouping with the layout of the bathrooms and observing the

following guidelines:Placing of plumbing fixtures around an easily accessible pipe shaft; in

high rise buildings the pipe shafts may have to be within the building

envelope and easy provision for access panels and doors should be

planned in advance, in such cases.Adopting repetitive layout of toilets in the horizontal and vertical

directions.Avoiding any conflict with the reinforced cement concrete structure by

avoidingembedding pipes in it, avoiding pipe crossings in beams,

columns and majorstructural elements.


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Identifying open terraces and areas subject to ingress of rainwater

directly orindirectly and providing for location of inlets at each level for

down takes fordisposal at ground levels.

PLANNING DESIGN CRITERIA: RAIN WATER DRAINAGERain-water should preferably be dealt separately from sewage

and sullage. Sewage and sullage shall be connected to sewers. However,

storm water from the courtyard may be connected to the sewer where it

is not possible to drain otherwise; after obtaining permission of

the Authority.The following requirements are suggested to be considered in the design

of drainage system:The layout shall be as simple and direct as practicable.The pipes should be laid in straight lines, as far as possible, in both

vertical andhorizontal planes.Anything that is likely to cause irregularity of flow, as abrupt changes

of direction, shall be avoided.The pipes should be non-absorbent, durable, and smooth in bore and

of adequate strength.


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The pipes should be adequately supported without restricting

movement.Drains should be well ventilated, to prevent the accumulation of foul

gases and fluctuation of air pressure within the pipe, which could lead

to unsealing of gully or water-closet traps.All the parts of the drainage system should be accessible for feasibilityof inspection and practical maintenance.

No bends and junctions whatsoever shall be permitted in sewers except

at manholes and inspection chambers.Sewer drain shall be laid for self-cleaning velocity of 0.75,m/s

and generally should not flow more than half-full.Pipes crossing in walls and floors shall be through mild steel sleeves of

diameter leaving an annular space of 5 mm around the outer diameter of

the pipe crossing the wall.Pipes should not be laid close to building foundation.Pipes should not pass near large trees because of possibility of damage

by theroots.


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Branch connections should be swept in the direction of flow.

Planning Design Criteria

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