Layout .1 General

Rain-water should preferably be dealt separately from sewage and sullage. Sewage and sullage shall be connected to sewers. However, Storm water from the courtyard

a) The layout shall be as simple and direct as practicable.

b) The pipes should be laid in straight lines, as far as possible, in both

e) The pipes should be adequately supported without restricting movement.

f) Drains should be well ventilated, to prevent the accumulation of fowl gases and fluctuation of air pressure within the pipe, which could lead to unsealing (siphoning) of gully or water-closet traps.

g) All the parts of the drainage system should be accessible for feasibility of inspection and practical maintenance.

h) No bends and junctions whatsoever shall be permitted in sewers except at manholes and inspection chambers.

j) Sewer drain shall be laid for self-cleaning velocity of 0.75 m/s and generally should not flow more than half-full.

k) 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.

m) Pipes should not be laid close to building foundation.

n) Pipes should not pass near large trees because of possibility of damage by the roots.

p) Branch connections should be swept in the direction of flow.

q) Sewer pipes should be at least 900 mm below road and at least 600 mm below fields and gardens.

r) Pipes should not pass under a building unless absolutely necessary.

56

Where it is necessary to lay pipes under a building, the following conditions shall be observed:

1) Pipes shall be Centrifugally cast (spun) iron pressure pipe as per good practice [9-2(9)];

2) The pipe shall be laid in straight line and at uniform gradient;

3) Means of access in form of manholes/inspection chamber shall be provided at each end, immediately outside the building;

4) In case the pipe or any part of it is laid above the natural surface of the ground, it shall be laid on concrete supports, the bottom of which goes at least 150 mm below the ground surface.

NOTE – It is desirable that pipe/drains should not be taken through a living room or kitchen and shall preferably be taken under a staircase room or passage.

s) Consideration shall be given to alternative layouts so as to ensure that the most economical and practical solution is adopted. The possibility of alterations shall be avoided by exercising due care and forethought.

4.5.2.3 Protection against vermin and dirt

The installation of sanitary fittings shall not introduce crevices which are not possible to inspect and clean readily.

Pipes, if not embedded, shall be run well clear of the wall. Holes through walls to lay pipes shall be made good on both sides to prevent entry of insects. Materials used for embedding pipes shall be rodent-proof. Passage of rodents from room-to-room or from floor-to-floor shall be prevented by suitable sealing. The intermediate lengths of ducts and chases shall be capable of easy inspection. Any unused drains, sewers, etc, shall be demolished or filled in to keep them free from rodents.

All pipe shafts shall be plastered before any pipes are installed in the shaft. It is advisable to lay pipes on the steel supports with adequate gap between plastered wall and support structure. This will provide a smooth surface and prevent location for survival of insects and vermins.

4.5.2.4 Choice of plumbing system

In selecting one or more of the type of piping systems, the building and the layout of toilets; relationship with other services; acceptability to the Authority; and any special requirements of users, shall be studied.

a) Two stack system

1) Two stack System with Common Vent – A system in which there is one soil pipe into which all water closets, urinals and any other soil appliances discharge. Additionally there is one waste stack into

57

which all non-soil waste such as baths, sinks, and basins are discharged through deep seal trap. In addition, there is a relief vent, which ventilates traps of water closets/ soil stack and also vents connection from waste appliances/ stack.

2) Two Stack System with Independent Vents - The system of plumbing in which soil and waste pipes are distinct and separate. Soil stack shall have discharge from water closets, urinals and any other soil appliances. Waste stack shall have discharge of non-soil waste such as baths, sinks, and basins through deep seal trap. Each soil and waste pipe shall have independent vents.

i) This system is ideal when the location of toilets and stacks for the WCs and waste fittings is not uniform or repetitive.

ii) In large buildings and houses with open ground and gardens the sullage water from the waste system can be usefully utilized for gardening and agriculture.

iii) In larger and multi storied buildings, the sullage is treated within the building for reuse as makeup water for cooling towers for air conditioning system and is also used for flushing water-closets provided it has absolutely no connection with any water supply line, tank or system used for domestic and drinking supply.

b) Single stack system

The one-pipe system in which there is no trap ventilation, the stack itself acts as vent through roof. In this system care shall be taken for proper sizing of the pipes and the trap arm distance. This system is restricted to residential occupancy up to 2 to 3 stories

1) This system is suitable for buildings where the toilet layouts and the shafts are repetitive. It requires less space, and is economical.

2) Continuous flow of water in the pipe from waste appliances makes it less prone to blockage and makes the system more efficient.

3) The system eliminates the need for a gully trap which requires constant cleaning.

4) The system is ideal when the main pipes run at the ceiling of the lowest floor or in a service floor. Two pipes system may; present space and crossing problems which this system eliminates.

c) Single Stack System Fully Ventilated

The system of plumbing in which the wastes from the sinks, baths and wash basins, and the soil pipe branches are all collected into one main pipe, which is connected, directly to the drainage system. The traps of the water closets, waste appliances etc., are completely ventilated with a separate pipe to preserve the water seal

58

1) The single stack system fully ventilated is ideal when the toilet layouts are repetitive and there is less space for pipes on the wall.

2) In any system so selected there should be not more than two toilet connections per floor.

3) The system requires minimum 100 mm diameter stack.

4) All the safeguards for the use of this system given in 4.5.2.4.1 shall be