Fixtures, Appliances, and Safety
Fixtures, Appliances, and Safety tests installation clearances, fixture selection, appliance connections, relief-valve discharge, and combustion safety. Expect practical scenarios about water closets, lavatories, shower valves, dishwashers, water heaters, and gas appliances.
Core rules
- Water closets need the code-required clearance from walls and adjacent fixtures; lavatories and showers have minimum spacing and height rules.
- Shower and tub-shower valves must be pressure-balanced or thermostatic and must limit hot-water temperature to prevent scald.
- A T&P relief valve discharge pipe must be the same size as the valve outlet, not reduced, terminate 6 to 24 inches above the floor or receptor, flow by gravity, have no trap, and not be threaded at the end.
- Appliances need backflow protection. A dishwasher drain needs a high loop or air gap; a clothes washer standpipe needs a trap and vent.
- Gas appliances require proper venting and combustion air; carbon monoxide alarms are a safety item.
Worked example
A 3/4-inch T&P valve on a water heater is piped with 1/2-inch copper to a floor drain. That is wrong twice: the discharge pipe is reduced, and the termination is not a proper air gap above a receptor. The correction is 3/4-inch pipe, full-size throughout, terminating 6 to 24 inches above the floor or receptor with an air gap, no trap, and no threaded end. Reasoning: the relief valve must discharge at full capacity without backpressure or blockage.
Traps that cost marks
- Reducing the T&P discharge pipe to fit an existing hole.
- Threading or capping the T&P discharge outlet.
- Omitting a trap or vent on a clothes-washer standpipe.
- Installing a shower valve without scald protection.
- Ignoring clearance dimensions around fixtures.