Fixtures, Fixture Fittings and Trim
What the code requires of a fixture
Fixtures must be of an approved type, have a smooth nonabsorbent surface, be supplied with hot and/or cold water as intended, be set level and secure, and be trapped unless they have an integral trap. Water closets are limited to 1.6 gallons per flush (1.28 for high-efficiency); urinals to 1.0 gpf. Access and clearance matter: a water closet needs about 15 in. from centerline to a side wall and 21 in. of clear space in front; accessible fixture heights and knee space are tested.
Connections
Supply connections use fixture stops, escutcheons at finished walls, and a trap with a water seal. A water closet sits on a closet flange fastened to the floor and sealed with a wax or elastomer gasket. Shower receptors require a sloped, watertight pan and a drain with a clamping ring; the pan is flood-tested before tile. Fixtures must be vented, and trap-arm limits from the vent tables still apply.
Traps
- Assuming a tub and shower, or a double sink, can share one trap. Each fixture gets its own trap; a continuous waste is allowed only within defined limits.
- Believing a floor drain needs no trap - it does, and it needs a trap primer if it can dry out.
- Forgetting the closet flange or the shower pan test.
- Overlooking that the flood level rim must be above any point where backflow could occur.
Rule of thumb
One fixture, one trap, one trap seal. If a fixture has an integral trap, it does not need a separate one - but the venting still must be correct.
Example: a double-compartment sink drains through a continuous waste to a single trap sized for the combined load, with the trap vented within the allowed trap-arm distance.