Pipe Joining, Fabrication and Installation
Scope
This domain tests threaded, solvent-welded, compression, flanged, welded and push-fit joints, plus cutting, bending, support and pressure testing. The exam focuses on joint preparation and cure times.
Core rules
- Cut square, deburr and clean the pipe end before joining.
- Threaded joints: use the correct die, apply PTFE tape 3–4 turns in the thread direction or an approved sealant, and do not over-tighten.
- Solvent-welded UPVC: clean, apply primer, apply cement evenly, push fully, quarter-turn and hold; allow the specified cure before testing.
- Flanged joints: use a matching gasket, align the flanges and tighten bolts in a star pattern.
- Support pipes at specified spacing; allow expansion and contraction.
- Pressure-test the completed section before concealment.
Worked example
Join two 50 mm UPVC pipes. Cut square, chamfer and clean the ends; mark insertion depth; apply primer to both surfaces; apply cement while wet; push fully and quarter-turn; hold about 30 seconds; wipe excess; allow the recommended cure before filling. Reason: primer softens the surface, cement fuses it, and the quarter-turn spreads cement without trapping air.
Traps
Skipping primer; too much cement; testing immediately; misaligned flanges; over-tightening plastic threads; no support.