Plumbing Fixtures, Fixture Fittings, and Fixture Traps
Fixture Requirements
Fixtures must be approved, have smooth and impervious surfaces, and be installed with proper clearance and access. Every fixture that discharges to the drainage system needs a trap, with limited exceptions (some fixtures with integral traps or those discharging to a floor drain). Questions test which fixtures require traps, minimum clearances, and accessibility requirements.
Fixture Fittings and Flow
Faucets, flush valves, and shower valves must meet flow and temperature limits. Shower valves must be pressure-balancing or thermostatic to prevent scald. Water closets have defined flush volumes. Traps in questions include confusing a fixture fitting with a trap, and forgetting that a fixture's trap must be accessible for cleaning.
Fixture Traps and Trap Seals
A fixture trap holds a water seal that blocks sewer gas. The seal depth is defined by code (commonly 2 to 4 inches). Traps must be self-cleaning and installed level. Questions test trap seal loss from siphonage, evaporation, or back pressure, and the prohibition on double-trapping and on trap arms that are too long.
Rule of Thumb
If a fixture connects to the drainage system and does not have an integral trap, it needs a trap. If a question describes sewer odor, think trap seal loss first: check for a dry trap, an improperly vented trap arm, or a double trap.
Worked Example
A rarely used floor drain in a mechanical room emits odor. The trap has dried out. The fix is to restore the seal by priming the trap, often with a trap primer, rather than adding a second trap.