Water Supply and Distribution Systems
Water Supply and Distribution Systems covers pipe selection, jointing, pressure control, and the details that keep potable water potable. The exam's favorite scenario is what happens on the downstream side of a check valve.
Materials and joints
- Copper (soldered, brazed, press), PEX (ASTM F877), CPVC, and galvanized are the usual choices; wetted surfaces must meet the lead-free definition (weighted average no more than 0.25% lead).
- Solder and flux must be lead-free; brazing is used where temperatures or standards demand it.
- PEX needs protection where it penetrates slabs or passes close to the water heater, and must be installed per its listing regarding sunlight exposure.
- Dielectric protection is required wherever copper meets steel.
Pressure control
- Install a pressure-reducing valve where static pressure exceeds 80 psi, and make it accessible.
- A PRV plus a backflow preventer creates a closed system: add a thermal expansion tank, or the water heater's T&P valve becomes the relief.
- Use water hammer arrestors near quick-closing valves, sized, not just installed.
- Booster pumps need a low-level cut-off and a bypass.
Worked example
A 90 psi street, a 1 in service, and a new RPZ: the device drops roughly 10-15 psi, so downstream static may be near 75 psi, still acceptable at the fixture. But the RPZ closes the system. A 50 gal heater raising water from 60 F to 140 F expands the volume about 1.5%, roughly 0.75 gal, which has nowhere to go without an expansion tank sized for that volume and the system pressure.
Traps
Ignoring thermal expansion, burying a PRV without access, using a bushing instead of a proper reducing fitting, and forgetting static head in a tall building.