Plumbing Fixtures, Appliances, and Specialty Systems
Fixtures: spacing, seals, and flow
Fixture questions reward memorized dimensions. Water closets need roughly 15 in. from the centerline to a side wall and about 30 in. of clear width, with front clearance in front of the bowl. Lavatories follow similar side-wall logic. Every fixture except a few listed exceptions must be trapped, with a 2–4 in. water seal.
Water efficiency is a reliable exam topic: water closets at 1.6 gallons per flush or less, urinals around 1.0 gpf, showerheads about 2.5 gpm at 80 psi, and faucets around 2.2 gpm. Accessible fixtures add height, clear-floor, and pipe-protection requirements.
Appliances
Water heaters need a temperature-and-pressure relief valve with a full-size discharge terminating safely - not capped, not trapped, not reduced, and not discharging where it can scald. Closed systems require an expansion tank. Know the air gap or air-gap-style backflow protection for dishwashers and the indirect waste arrangements for food service equipment, sterilizers, and ice machines.
Specialty systems
Grease interceptors sized for the fixtures served, floor drains with trap primers in dead areas, sump and sewage ejectors with proper venting, backwater valves, and drinking fountains. Fixtures that receive indirect waste must discharge through an air gap or air break into a properly trapped receptor - never directly connected.
Worked example
An inspector rejects a water heater install where the T&P relief discharges 6 in. above the floor through a reducing bushing. Two violations: the discharge line must be the full size of the valve outlet, and it must terminate in a safe, non-scalding location. Re-pipe in full size with a gravity drain to a safe point.