Plumbing Materials, Pipes, Fittings, and Joints
What the domain covers
Plumbing Materials, Pipes, Fittings, and Joints tests identification, suitability and joining of common pipes and fittings. You must know why GI, PVC, CPVC, PPR, CI and copper are used in different locations.
Core rules
- GI pipe is threaded and used for cold-water supply and some fire lines; it can corrode.
- PVC and uPVC are common for drainage and cold water; CPVC and PPR suit hot-water lines; CI is used for soil and heavy drainage; copper resists heat but needs specific joining.
- Fittings change direction, size or connection: 90° and 45° elbows, tees, reducers, couplings, unions, caps, bends, P-traps, floor traps and cowls.
- Joint methods include threaded, solvent-cement, compression, flanged, rubber-ring push-fit and welding. The method must match material and pressure.
- Deburr and clean before joining; support horizontal runs; allow expansion where required.
Worked example
Choose a pipe for a bathroom hot-water branch and a separate soil pipe. The hot branch should be CPVC or PPR because uPVC softens at hot-water temperature; the soil pipe should be PVC soil/waste or CI because it carries solids and needs durable drainage fittings. The hot joint uses solvent cement suitable for CPVC or a push-fit/compression system rated for temperature; the soil joint uses solvent cement or rubber-ring push-fit as specified. The reasoning is temperature, pressure and waste load, not price alone.
Traps that cost marks
Using PVC solvent cement on CPVC, cementing a threaded GI joint, mixing materials without an adapter, forgetting primer, applying excess cement inside the socket, and omitting expansion gaps or supports.