Plumbing Fixtures and Appliances
Fixture questions blend code tables, clearances, and water conservation limits. Know the standard maxima: 1.6 gallons per flush for water closets (1.28 for WaterSense-labeled units, frequently required by local amendment), 1.0 gpf urinals, 2.2 gpm lavatory and kitchen faucets, and 2.5 gpm showerheads at 80 psi. A question showing a fixture that exceeds these limits is asking you to flag a violation.
Each fixture needs a trap, a trap seal of 2 to 4 in, and protection from backflow, either an air gap of at least twice the effective pipe diameter at a receptor or an indirect waste where food or sterilized equipment is involved. Floor drains in mechanical rooms and kitchens need trap primers so the seal does not evaporate.
Clearances and accessibility are high-yield. A water closet needs 15 in from centerline to any side wall and a 30 in wide space, with roughly 21 to 24 in clear in front. ADA work sets the lavatory rim at 34 in maximum, knee clearance 27 in high by 30 in wide, grab bars 33 to 36 in above the floor, and controls within a 15 to 48 in reach range.
Fixture counts come from occupant load and occupancy classification: compute total occupants, split by sex where required, then divide by the ratio in the table and round up.
Worked example: a 100-occupant assembly space with a 50/50 split and a ratio of 1 water closet per 25 women needs 50 divided by 25 = 2 water closets. A fraction of a fixture is always a whole fixture.