Sump pumps usually purr along for years without a glitch. When problems do occur, you can generally identify and repair them easily if you know what to look for (see chart). The following steps describe how to handle the two most common problems.
To add a check valve to a line that doesn't have one, purchase a valve no smaller in diameter than the existing drain pipe and any required couplings or adapters. Use a hacksaw or pipe cutter to cut out a section of pipe to accommodate them. Deburr the cut edges with a metal file or utility knife. Go to step 3.
To remove a check valve secured with a flexible coupling or adapter, loosen the steel strap with a flathead screwdriver and twist it off. If it is welded or glued together, cut the pipe with a hacksaw. If the valve was incorrectly installed and you need to reverse it, leave about 2 inches (5 cm) of pipe on each end of the valve. Otherwise cut close to the valve and discard it.
To install a new valve, slide one flexible coupling over the pipe that connects to the pump and another over the pipe that connects to the drain. Insert the valve with the direction-of-flow arrow facing away from the pump. To reinstall a valve after reversing its direction of flow, slide the coupling over the pipe stubs on the valve and tighten the straps.
Unplug and disconnect the pump from the discharge piping, then lift it out of the sump.
Remove the housing to access the screen and impeller; typically it snaps or bolts into place, so you may need a wrench.
Remove any debris, rinse the screen and carefully pry out any obstacle jamming the impeller.
Clean the sump pit before reinstalling pump.