Plumbing, Sanitary and Electrical Fittings
What this domain tests
The exam covers pipe materials and fittings, drainage systems and traps, sanitary fixtures, and basic domestic wiring with protection and earthing.
Core rules and concepts
- Pipes: GI (IS 1239), CPVC for hot and cold water, PVC SWR for soil, PVC for waste, HDPE underground; common sizes 15, 20, 25 and 32 mm.
- Fittings: elbow, tee, reducer, union, bend, cowl, bib cock, stop cock, ferrule.
- Traps: a P-trap or S-trap holds a water seal of 40–50 mm that blocks sewer gas; nahani trap at floor level; gully trap receives waste water; inspection chamber at junctions and changes of direction.
- Systems: two-pipe system separates soil and waste; one-pipe system uses a single stack with a vent pipe.
- Electrical: 230 V single phase, 415 V three phase; concealed conduit wiring; MCB distribution board; lighting circuits in 1.5 mm² cable, 6 A sockets in 2.5 mm², 16 A power points in 4 mm².
- Earthing: pipe or plate earthing; earth resistance kept as low as practicable, typically under 5 Ω for domestic installations; earth wire is green.
Worked example
A house for 4 persons at 135 litres per head per day = 540 litres daily demand. For one day of storage plus about half a day standby, provide a 1000-litre overhead tank. The reasoning - demand, then storage, then the next standard tank size - is what the examiner wants.
Traps that cost marks
Omitting the water seal; connecting soil and waste into one pipe without a vent; confusing live (brown/red), neutral (black/blue) and earth (green); sizing a tank from pipe diameter instead of daily demand.