Water Supply Systems and Plumbing Layouts
Domain 8 tests how water reaches a fixture: sources and storage, direct and indirect systems, distribution layouts, valves, backflow protection, and demand calculation.
Systems and layouts
- Direct supply from the mains, indirect through a sump and overhead tank, or boosted with a pump and pressure vessel.
- Layouts: trunk and branch, manifold, and loop; dead legs are avoided because water stagnates in them.
- Fittings: ferrule, water meter, stop cock, gate valve, float valve, NRV, pressure-reducing valve, bib cock, angle valve.
Design rules
- IS 1172 uses 135 litres per capita per day for domestic supply; provide at least one day of storage.
- Fit a float valve and an overflow with an air gap; never cross-connect potable and non-potable lines.
- An NRV on the pump discharge prevents backflow; support pipes and allow for expansion on hot lines.
- Water hammer is reduced with slow-closing valves and air chambers.
Worked example
Size an overhead tank for five people with two days of storage. Reasoning: 135 litres per person per day × 5 = 675 litres per day; two days gives 1,350 litres, so the next standard tank is 1,500 litres. Check that the tank gives working pressure at the topmost tap and that the slab can carry the filled weight, about 1,500 kg of water plus the tank.
Traps
Guessing tank size; omitting the overflow air gap; fitting a gate valve where a stop cock is wanted; leaving dead legs behind unused fittings.