There’s never a convenient time for sump pump failure. Sump pumps spend most of the time on standby, only actuating when they’re really needed as ground water rises up in the sump basin or indoor or outdoor flooding threatens the basement. If you live in your house long enough, a sump pump failure may occur. The U.S. Department of Housing and Urban Development states that the average service life of a residential sump pump is 10 years.

Here are some common causes of sump pump failure and what to do if it happens:

• Power outage. A severe storm threatens to flood your basement and—just when you need it most—the storm also knocks out grid power to the sump pump that protects your basement from flooding.
• Float switch or pressure switch failure. The presence of water in the basin is detected by the float switch or pressure switch that activates the pump. A defective switch is another common cause of sump pump failure.
• Clogged pump strainer. The intake strainer on the bottom of the pump may become clogged with debris that prevents water from entering the pump.
• Obstructed discharge pipe. Blockage in the pump discharge pipe prevents water from flowing to the outdoors. Instead, obstructed water flows backwards into the sump basin, causing the pump to reactivate continuously, eventually leading to sump pump failure.

What To Do Next

• A wet or flooded basement due to sump pump failure is very dangerous if electricity is still present in the space. Make sure electrical power is shut off at the main circuit breaker before entering the basement.
• If you have a wet/dry vacuum to remove shallow standing water—and/or mops—dry the basement as much as possible. If the basement has hinged ventilation windows, open them up and run fans to circulate air. 
• If basement flooding is more than minor, you’ll need professional water damage recovery services to remove the water safely and prevent subsequent mold contamination.
• If a power outage was the cause of sump pump failure, consider installing a new pump with a battery backup option.

If a sump pump failure occurs, will you find out the hard way? Installed inside a covered basin in the basement floor, sump pumps tend not to get much attention—until they fail, that is. When the basin overflows with infiltrating groundwater that didn’t get properly pumped out, or a water pipe ruptures and the pump doesn’t actuate to prevent major basement flooding, the situation suddenly becomes obvious.

Here are a few likely causes of sump pump failure:

• Clogged inlet screen. A screen on the inlet located at the bottom of the pump filters out debris that might clog the pump mechanism. If the pump screen and the basin aren’t cleaned at least once a year, debris accumulating on the screen may block the intake of water and the pump will fail to function when it’s needed.
• Faulty float switch. As the level in the pump basin rises, a float switch actuates the pump to remove water. A stuck or defective switch means the pump doesn’t turn on and the basin rapidly overflows, causing basement water damage before it’s noticed.  
• Burned out motor. While pump motors may fail simply from age, another cause is a defective float switch. In this case, the switch may actuate the pump correctly but fail to turn the pump off. The pump runs continuously and overheats, eventually failing completely. Because it’s installed in a basin down in the basement, a continuously running sump pump is often not obvious to residents upstairs.   
• Defective backflow valve. As the pump empties the basin and turns off, a backflow valve located in the discharge line prevents water from flowing backward into the basin. If this valve is faulty, backflow into the basin will quickly trigger the pump to actuate again. The pump empties the basin, turns off, then activates again immediately due to backflow entering the basin. This continuous on-off-on operation will cause the pump to fail prematurely.

Annual sump pump maintenance is a good practice to ensure that when the pump’s needed most, it will do the job. Sump pump maintenance is typically provided by a qualified local plumber.