Water Supply Systems: Materials, Installation, and Testing
What the exam tests
This domain covers approved potable-water materials, joining methods, support and protection, pressure testing, and disinfection. The exam expects you to protect water quality from the meter to the fixture.
Core rules
- Use approved materials for potable water: copper, PEX, CPVC, and galvanized steel where allowed. Solder and flux must be lead-free.
- Join dissimilar metals with dielectric unions or approved isolation fittings to limit galvanic corrosion.
- Protect PEX from UV, freezing, and physical damage; support pipe at code spacing and allow for expansion.
- Keep water lines separated from sewer lines and protect them from contamination during repair.
- Test before concealment. Hydrostatic testing uses potable water at the code-required pressure and duration; air testing only where approved.
- Disinfect new or repaired potable lines. A common method is 50 ppm chlorine for 24 hours or 200 ppm for 1 hour, followed by flushing.
Worked example
A water line is tested at the top of a 24-ft rise. To hold 100 psi at that high point, the gauge at the low point must read 100 + (24 / 2.31) = 100 + 10.4 = 110.4 psi. If the tester reads only 100 psi at the bottom, the high point has about 89.6 psi and the test does not prove 100 psi throughout.
Traps that cost marks
Using air when water is required; failing to disinfect after a repair; connecting copper directly to steel; supporting PEX too far apart; leaving a test gauge at the low point and assuming the high point is the same.