Installation and Testing of Plumbing Fixtures, Appliances, and Accessories
Fixtures, appliances, and accessories
This domain tests setting out, rough-in, connection, sealing, and testing of water closets, lavatories, sinks, floor drains, and appliances. Correct height and alignment matter as much as a leak-free joint.
Core rules
- Confirm the rough-in before setting a fixture: water closet rough-in is measured from the finished wall to the closet flange center; common sizes are 300 mm and 400 mm.
- Set fixture heights to the specification or accepted standard: lavatory rim around 800 mm, kitchen sink around 900 mm, and floor drains flush with the finished floor at the low point.
- Use the correct gasket, wax ring, or sealant; do not rely on grout or silicone to bridge a gap.
- Provide supply stops and accessible connections; use escutcheons at finished walls.
- Support fixtures independently of the pipe; do not hang a fixture from its supply or drain.
- Test each fixture after connection: fill, flush, and check for leaks at supply, drain, and seal.
Worked example
A closet flange center is 310 mm from the finished wall. A 300 mm rough-in water closet is selected; the 10 mm difference is taken up by the flange and wall finish, not by forcing the bowl. The candidate sets the flange level with the finished floor, installs a new wax ring, sets the bowl, tightens bolts evenly, and connects the supply. The reasoning links the measured rough-in to the fixture's specified rough-in.
Traps
Using the unfinished wall for rough-in, setting a flange below the floor, over-tightening a plastic supply nut, omitting a trap seal, and testing only the drain are common mistakes.