Plumbing, Water, and Sanitation Systems
This domain covers fresh water supply, waste water, and everything between: pumps, heaters, tanks, valves, vents, and winterizing. Exam items focus on how each subsystem behaves under pressure, what happens when it is neglected, and the correct sequence for service and storage.
Fresh water
- PEX is the standard pipe, joined with crimp rings or expansion fittings. Support it about every 32 inches.
- A demand pump holds roughly 45 to 55 psi with a pressure switch and an accumulator to stop rapid cycling.
- The city water inlet has a check valve that prevents backflow into the tank and pump.
- Water heaters hold 6 or 10 gallons, use a bypass kit for winterizing, and carry a TPR valve. Suburban units have a sacrificial anode rod to check yearly; Atwood units use a nylon drain plug.
- Winterizing uses propylene glycol RV antifreeze with burst protection near minus 50 degrees F. Drain low points, bypass and drain the heater, run antifreeze through every fixture, and leave it in the traps.
Waste
- The black tank valve is 3 inch, the grey valve 1.5 inch. Dump black first, then grey to rinse the hose.
- Never leave the black valve open at a full hookup. Liquids drain away, solids stack up, and the tank pyramids.
- Holding tank vents exit the roof. A mud dauber nest in the vent causes slow draining and odour; air admittance valves under sinks let traps breathe.
- Tank sensors are conductance probes. Paper and sludge bridge them and produce false readings.
Worked example
How much antifreeze does a winterizing job need? Half-inch PEX has an ID near 0.485 in, so each foot holds about 2.2 cubic inches, or roughly 0.01 gallon. A 40 ft run is 0.4 gallon. Add three P-traps at about 0.1 gallon each, the toilet valve, and the pump head, and the job needs about 1.5 to 2 gallons with margin. The heater, being bypassed and drained, contributes almost nothing.
Traps
- Dumping grey before black, leaving solids in the hose.
- Using automotive antifreeze, which is toxic, or watering down RV antifreeze.
- Pressurizing the system before closing the low-point drains.
- Forcing a toilet seal onto a damaged flange instead of replacing the flange.