Plumbing, Sanitation and Electrical Services
Plumbing, Sanitation and Electrical Services tests the design and installation of water supply, drainage, sanitary fixtures and basic electrical circuits in buildings. Expect questions on pipe sizes, traps, ventilation, septic tanks, earthing, protective devices and IS/NBC requirements.
Water supply and drainage
- Water supply: estimate demand from occupancy and per-capita allowance; provide storage and distribute through appropriate pipe sizes. IS 1172 gives basic requirements for water supply, drainage and sanitation.
- Drainage: soil and waste pipes discharge to a gully or inspection chamber. Every fixture needs a water seal trap; provide ventilation pipes to protect seals.
- Septic tank: receives sewage, retains solids and discharges clarified liquid to a soak pit or drain field; sludge must be removed periodically.
Electrical services
- Wiring: IS 732 covers wiring installations; use proper circuit protection, conduit and earthing.
- Earthing: IS 3043 covers earthing; earth resistance should be low, commonly not more than about 5 Ω for domestic installations, and must be tested.
- Protection: MCB protects against overload and short circuit; RCCB/ELCB protects people against earth leakage.
Worked example
A hostel has 20 occupants at 135 litres per capita per day. Daily demand = 20 × 135 = 2,700 litres = 2.7 m³. If one day's storage is required, provide an overhead tank of at least 2.7 m³ plus a small freeboard; a 3,000-litre tank is a practical selection.
Traps
Do not omit trap seals or vent pipes; do not size a septic tank only by user count without checking retention and sludge volume; do not confuse MCB and RCCB functions; and never rely on a pipe or metallic conduit as the sole earth path.