Sanitary Fittings, Fixtures and Appliances
What the exam tests
This domain covers water closets, wash basins, sinks, urinals, baths, traps, taps, valves and flushing appliances. The exam tests correct selection, outlet sizes, trap protection and installation checks.
Core rules
- Typical fixture outlets: WC 100 mm, wash basin 32 mm, sink 40 mm, urinal 50 mm; confirm the manufacturer’s data.
- Every fixture must have a water seal, commonly at least 50 mm, to stop sewer gas.
- Use a P-trap or bottle trap with a cleaning eye; avoid an S-trap because it is more prone to siphonage.
- A flush valve needs adequate pressure; a cistern suits low-pressure areas.
- Provide an air gap or backflow device where a hose or appliance could contaminate potable water.
- Keep access for cleaning and maintenance; do not bury traps in masonry.
Worked example
A wash basin wastes slowly and smells. The existing trap is a shallow, badly aligned fitting. Replace it with a 32 mm bottle or P-trap with a 50 mm seal, align the outlet, slope the waste branch toward the stack, hand-tighten the unions and fill-test for leaks. Reason: the seal blocks gas, the slope carries waste, and the access nut allows cleaning.
Traps
No trap or a dry trap; too small a waste; a trap buried without access; using a WC outlet for a basin; ignoring flush-valve pressure requirements.