Plumbing Fixtures, Appliances, and Specialty Systems
Fixture requirements and clearances
Codes set minimum fixture counts by occupancy, minimum spacing, and installation height. Water closets need roughly 15 inches clear from the centerline to a side wall and 21 inches in front; lavatories and sinks must be sealed to the wall or countertop. Water closets today are low-flow, and the fixture must be listed and installed per its listing and the manufacturer's instructions - instructions are part of the code.
Accessibility (ADA) traps
Accessibility questions test reach ranges and clearances: lavatory rims generally not more than 34 inches above the floor, water closet seats 17 to 19 inches high, grab bars at 33 to 36 inches, knee and toe clearance under sinks with insulated drain pipes, and controls operable without tight grasping. Distinguish ADA from plumbing-code clearances - a question may offer a plumbing-code number as a distractor for an accessible fixture.
Appliances and specialty systems
Water heaters: T&P relief valve piped full-size, gravity-drained, terminating not more than 6 inches above the floor or receptor, with no threads or valves on the discharge and no trapping. A drain pan at least 1½ inches deep is required where leakage would cause damage. Know dishwasher air gaps or high loops, clothes washer standpipes with trap and vent, floor drains with trap primers, drinking fountains, hose bibbs with vacuum breakers, grease interceptors, and medical gas or fuel gas as separately regulated systems.
Traps
Reduced-size relief discharge piping, a plugged or capped T&P outlet, missing trap primers, and fixtures installed without access for repair. Worked example: a roof-level water heater in a Florida condo needs a pan with a drain to a safe location, a T&P piped to within 6 inches of the pan, and an expansion tank if a backflow preventer closes the system.