Diagnose and replace a bad ejection pump switch
When sewage ejection pumps fail, you can quickly have an ugly mess on the basement floor. Before you panic and call the plumber (minimum charge $250), make sure the “float” switch works. Most sewage ejector pumps and some sump pumps have a floating ball attached to the pump by a separate electrical cord—if you see two cords coming out of the basin, you have a float switch. This switch activates the pump when the water reaches a certain height. The switch is plugged in with a “piggyback” plug, and the pump is plugged into the back of it so it doesn't turn on until the switch does (Photo 1). Unfortunately, these switches may only last half as long as the pump, according to manufacturers. However, universal replacement switches are available at home centers and plumbing suppliers for $20, and replacing the switch is simple.
First check the circuit breaker and GFCI outlet. If they're OK, unplug the pump from the back of the piggyback plug and plug it in directly. If the pump kicks on, the switch is bad. If it doesn't turn on, the pump is bad, but replacing it ($300, including switch) is just as easy as replacing the switch—simply lift out the old pump and put a new one in.
If the pump works, run water for a minute to flush out the dirty water—but don't let the water level go below the pump or you'll burn out the pump. Then remove the basin top. Pull the vent pipe from the top and loosen the coupling or union that joins the waste line together (wrap a towel around the pipe to catch any water).
Lift out the pump and mark the point where the cord that holds the switch is attached to the pump. Attach the new switch at the same point so it will turn on and off at the same water level (Photo 2). Also check to be sure there's an air bleed hole near the bottom of the waste pipe (another potential cause of pump failure). If you don't see one, drill a 1/16-in.-diameter hole into the waste pipe about 2 in. from where it enters the pump.
Put the pump back in the basin and reassemble the plumbing. Make sure the float switch moves freely and doesn't get wedged against the sides. Seal around the edge of the basin with silicone caulk if the original gasket or seal is deteriorated.
Figure A: Sewage Pump System
When the water level rises, the floating switch turns on the pump, which grinds waste and ejects it up the waste line. The check valve stops wastewater from flowing back into the basin. The shutoff stops backflow when the pump is serviced.