Plumbing, Sanitary and Water Supply Works
This domain tests pipe materials, fittings, slopes, traps, fixtures and the tests that prove a system is watertight and safe.
Pipes and fittings
GI for exposed supply, PVC for drainage, CPVC and UPVC for hot and cold supply, HDPE for underground mains. Fittings include elbow, tee, reducer, union, bend, cap, coupler and valve. The soil pipe of 100 to 110 mm carries WC discharge; waste pipes of 32 to 50 mm carry sink and basin waste; the vent pipe equalises pressure and protects the water seal.
Water seal and slope
Every fixture needs a trap with a water seal of about 50 mm to stop sewer gas entering the building. Drainage falls by gravity, about 1:60 to 1:100 for small-bore pipe. Lay pipes in the direction of flow, use 45 degree junctions rather than 90 degree tees, and provide rodding eyes at changes of direction.
Worked example
A 12 m drain run at a 1:80 gradient. Fall = 12 divided by 80 = 0.15 m, that is 150 mm. If the invert at the start is 0.60 m below floor level, the invert at the end is 0.75 m below. Check that the run still connects above the public sewer and below the lowest fixture.
Fixtures and testing
WC, wash basin, sink, floor trap, kitchen waste and rainwater downpipe. Test supply pipes hydraulically at about 1.5 times working pressure, and test drains with water or air before covering. Support pipes at recommended spacing and protect them from traffic load.
Traps
Using a 90 degree elbow where a 45 degree bend with access is needed, forgetting the vent pipe, laying drains level, and confusing soil and waste pipe sizes.