Pumps, Hydronics, and Specialty Plumbing Systems
Specialty questions reward hands-on experience: sump and sewage pumps, condensate removal, booster systems, hydronic loops, and California's graywater and rainwater rules.
Pumps and lift stations
- Sewage ejector basins need a gas-tight cover, a dedicated vent (2 inch minimum) run full size to open air, a check valve, a gate valve and an alarm; duplex systems alternate the pumps.
- Size the discharge to the drainage fixture-unit load: a 2 inch discharge handles a 6 DFU basement bathroom at 1/4 inch per foot.
- Condensate drains run 3/4 inch minimum at 1/8 inch per foot to an indirect waste, or through a listed condensate pump.
- Booster and constant-pressure pumps need a low-water cutoff, a bypass, and backflow protection on the suction.
Hydronics
A closed loop carries a boiler, circulator, expansion tank (roughly 4 percent of system volume), air separator, fill valve with RPZ or air gap, relief valve (30 psi on a residential boiler), zone valves and balancing devices. Fill cold to about 12 psi; design temperature difference is commonly 20 degrees F. Radiant PEX must have an oxygen barrier.
Graywater and rainwater
CPC appendices govern these systems when the AHJ adopts them. Both require a three-way diverter, no cross-connection to potable water, subsurface irrigation with setbacks from wells and slopes, and labeling. Simple graywater systems below the Health and Safety Code threshold still must follow the standards.
Worked example
A basement bath (WC 3 DFU + lavatory 1 + shower 2 = 6 DFU) drains to a new ejector. A 2 inch discharge is adequate at 6 DFU. Required head = 9 ft vertical lift + 4 ft equivalent friction = 13 ft. Select a pump delivering about 20 gpm at 13 ft, add a check valve, gate valve, 2 inch vent and high-level alarm, and confirm basin volume allows reasonable cycling.
Traps
- Venting an ejector basin through the building vent, or omitting the vent.
- No check valve, so the basin refills on every cycle.
- Feeding a boiler from potable water without backflow protection.
- Omitting or undersizing the expansion tank on a closed loop.