Pipe Materials and Fittings
Pipe Materials and Fittings tests joining methods, material compatibility, pressure ratings, and corrosion control. The exam expects you to choose the right fitting and method for copper, PEX, CPVC, PVC, ABS, cast iron, and steel without mixing incompatible systems.
Core rules and concepts
- Copper to steel connections need a dielectric union or approved isolation to reduce galvanic corrosion.
- PVC and ABS use solvent cement and primer appropriate to the material; do not mix PVC cement with ABS fittings.
- PEX requires approved insert or crimp fittings and must be protected from UV, freezing, and physical damage where required.
- Soldered copper joints must be clean, fluxed correctly, and heated evenly; lead-free solder is required for potable water.
- Fittings must match the pipe material, size, and pressure rating; reducing fittings and direction changes must be approved for the application.
Worked example
A copper water line is connected directly to a galvanized steel nipple. The dissimilar metals create a galvanic cell, and the steel will corrode. The correct detail is a dielectric union or approved dielectric nipple between them, installed so the metals do not touch. Simply wrapping the joint with tape does not replace an approved dielectric fitting.
Traps that cost marks
Do not assume all plastic pipe uses the same cement. Do not use a drain fitting on a pressurized water line. Do not solder near flammable material without protection. Do not ignore manufacturer crimp-tool calibration for PEX.
Exam focus
Know the common joining methods and the corrosion risk from dissimilar metals. Material questions usually hinge on compatibility, not brand names.