Pipe Materials, Fittings and Jointing
Core concepts
Candidates must match material to service: copper for potable supply (types K, L, M differ in wall thickness, K heaviest), PEX for flexible supply, PVC and ABS for drainage, cast iron for soil and waste where sound or fire performance matters, galvanized steel for older supply, and CPVC for hot water where permitted. Know the fittings: coupling, elbow (90 and 45), tee, wye, reducer, union, cap, and the difference between a sanitary tee and a vent tee. Joint methods matter: soldered copper, press-fit, solvent cement for PVC and ABS, threaded steel, push-fit, and mechanical couplings.
Traps in questions
A frequent trap is confusing PVC and CPVC solvent cements - they are not interchangeable. Another is assuming any copper type can be buried; codes restrict some types in slabs. Watch for questions about dielectric unions between copper and steel to prevent galvanic corrosion, and about transition fittings between plastic and metal. Also expect items on which fitting is legal for a horizontal-to-vertical change of direction - a wye with a bend, not a sanitary tee.
Worked example
Rule of thumb for solvent cementing: cut square, deburr, dry-fit, apply primer, then cement with a full even coat, push and twist a quarter turn, and hold for about 15 seconds before handling. Allow the joint to cure before pressure testing; cure time increases with pipe diameter and decreases with temperature.