Plumbing Works and Pipe Fitting
Plumbing Works and Pipe Fitting tests jointing, bending, support and testing of pipework. The exam expects you to know why a joint fails and how to sequence work so that a line can be tested and commissioned.
Jointing methods
- GI: cut, ream, thread with a BSP die, apply jointing compound or PTFE tape, tighten with a pipe wrench; avoid over-tightening.
- PVC-U/CPVC: clean, apply primer, apply solvent cement, push fully, hold, and cure before pressure.
- Copper: solder with flux and lead-free solder; braze for higher temperatures.
- CI: caulk lead or cement, or use a mechanical coupling.
Support, slope and expansion
Support horizontal runs at approved intervals; allow expansion loops or sockets on hot-water lines; keep bends sweeping. Drainage needs a steady fall, typically 1:60 to 1:100 for small branches, and vents to protect trap seals.
Worked example
A 6 m drainage branch must fall at 1:60. Fall = length ÷ slope denominator = 6 m ÷ 60 = 0.10 m = 100 mm. Set the upstream invert, then lower the downstream invert by 100 mm; do not use a steeper random slope.
Traps
Threading PVC; failing to ream GI; not allowing for expansion; jointing and immediately pressure-testing solvent-welded pipe; and using a reducing fitting where a proper reducer is needed.