Uniform Plumbing Code - Plumbing Systems and Fixtures
What this domain covers
This domain tests fixture requirements: minimum facilities by occupancy, clearances, trap and drain connections, indirect waste, backflow protection at fixtures, and water heater installation. Fixture questions often combine a layout sketch with a code rule, so identify the fixture type and occupancy first.
Core rules
- Provide the minimum fixtures for the occupancy. A single-family dwelling needs at least one water closet, one lavatory, one bathtub or shower, and one kitchen sink.
- Respect fixture clearances and installation dimensions: water closets need side clearance and center-to-center spacing; lavatories, bathtubs and showers need usable space and protective surfaces.
- Each fixture must be trapped. Traps must be self-cleaning with a proper water seal; trap arms are limited by pipe size and must be vented. S-traps, double trapping and crown-vented traps are prohibited.
- Food equipment, ice machines, dish sinks and similar fixtures receive indirect waste through an air gap or air break to a receptor, not a direct connection.
- Water heaters need a temperature-and-pressure relief valve, a discharge pipe to a safe place, a drain pan where leakage would cause damage, seismic restraint where required, and thermal expansion control on a closed system.
Worked example
An ice machine in a restaurant has a 1-inch drain piped directly into a floor drain receptor. That direct connection is wrong. Potable ice equipment is a contamination risk, so the drain must discharge indirectly through an air gap or air break to the receptor. The inspector should require the indirect connection before approving the fixture.
Traps that cost marks
Measuring clearance from the wall face instead of the fixture centerline; using one trap for two fixtures; omitting a trap primer for a floor drain; confusing an air gap with an air break; and installing a water heater without a drain pan or relief discharge.