Sanitary Fixtures
What this domain tests
Sanitary Fixtures covers water closets, wash basins, sinks, urinals, showers, floor drains and their traps. The exam tests installation heights, clearances, flushing, trap seals and the connection between fixture and drainage.
Core rules
- Every fixture that discharges to drainage needs a trap; the trap seal must be maintained and protected from siphonage.
- A water closet needs a flushing cistern or flush valve with the correct discharge and an accessible isolation valve.
- Wash basins and sinks need an overflow and a trap; the waste pipe must be sized to the fixture outlet.
- Urinals need flush control and a trap; floor drains need a removable strainer and a trap.
- Keep fixture clearances and heights usable: basins usually around 800 mm rim height, WCs with adequate side clearance and door swing.
- Support fixtures securely; seal wall joints with a flexible sanitary sealant, not grout that cracks.
Worked example
A rarely used basin smells of sewer. It has a bottle trap, but the trap seal has evaporated because no water has run for weeks. The reasoning is seal loss by evaporation, not necessarily a blocked vent. Run water to refill the trap, check for leaks, and fit a trap primer or choose a fixture/trap arrangement that keeps the seal wet.
Traps
Double-trapping a fixture, connecting a basin waste to a soil stack without a trap, using a shallow trap on a WC, and sealing a trap access plug permanently are common errors.