Plumbing Fixtures and Fixture Fittings
Plumbing Fixtures and Fixture Fittings
This domain tests fixture selection, rough-in dimensions, flow rates, and fittings. Expect questions on water closets, lavatories, sinks, showers, and accessible installations.
Core rules
- Water closets commonly require a 12 in rough-in from the finished wall, 15 in from center to side wall, and 30 in of clear width.
- Lavatory faucets are limited to about 1.5 gpm, showerheads to about 2.0 gpm at 80 psi, and water closets to 1.28 gpf in current high-efficiency designs.
- Fixture fittings include stops, supply tubes, tailpieces, traps, escutcheons, and carriers; access must be maintained for repair.
- Install fixtures level, secure, and sealed to the finished surface; use a closet flange and wax or waxless seal for water closets.
- Accessible fixtures require clear floor space, insulated supply and drain pipes under lavatories, and controls within reach.
Worked example
A lavatory is set in a 30 in vanity. The drain is 1-1/2 in and the trap is a P-trap. The faucet is rated 1.5 gpm. The installation is acceptable if the trap arm is vented within 6 ft, the stop is accessible, and the drain opening is sealed. If the faucet were 2.2 gpm, it would fail the current flow limit for a residential lavatory.
Traps that cost marks
Using the wrong closet rough-in, installing a fixture without a shutoff stop, connecting a dishwasher without a high-loop or air gap, and leaving a trap union inaccessible behind a finished wall.