Why won't my sump pump turn on?

The short answer

A sump pump that will not turn on has usually lost power, has a float that cannot rise, or is not seeing enough water to start. Wayne's troubleshooting chart lists the causes of a pump that will not start or run in this order: water level too low, a blown fuse or tripped breaker, low supply voltage, the motor, the switch, a clogged inlet screen, and an obstructed switch.^[1] You can check most of those yourself. The two that need a pro are low voltage and a dead motor.

If there is water on the floor

Deal with this before you touch an outlet, a breaker or the pump. Wayne's rule: do not walk on the floor when water is present until all power is turned off, and if the electric panel is in the basement, call an electrician.^[1] FEMA says the same for any equipment: "Do not touch electrical equipment if it is wet or if you are standing in water."^[4]

First, is it meant to be running?

A pump only starts when water lifts its float to the on level. Wayne's chart notes that water must be at the appropriate level to activate the switch.^[1] In a dry spell the pit may sit almost empty for weeks. Pour a bucket of water in: if the pump starts, drains the pit and stops, it is working.

Power: the most common cause

The GFCI outlet tripped. Wayne says the receptacle must be protected with a ground fault circuit interrupter (GFCI),^[1] and those outlets trip in damp basements. Wayne warns: "In damp areas, GFCI breakers may trip, effectively shutting off the sump pump."^[1] Press the reset button. If it will not reset, or trips again as soon as the pump starts, either the outlet or the pump is faulty.

A breaker tripped or a fuse blew. Check the panel. For a blown fuse or tripped breaker, Wayne's advice is to determine the cause, then either replace it with a properly sized fuse or reset the breaker.^[1] A breaker that keeps tripping is telling you something; do not keep resetting it.

Low voltage. Wayne's remedy for low supply voltage is to contact an electrician.^[1] Lights dimming when the pump tries to start is one hint.

The float cannot rise

If the pump has power but does not react to rising water, look at the float. Wayne warns that vibration can make a pump fall or tilt onto one side and jam the float so it cannot start the pump.^[1] A cord drifting into the float's path, a float rubbing the pit wall, or silt on the float's rod does the same thing. Unplug the pump before reaching into the pit. Our guide to fixing a stuck sump pump float switch walks through freeing it.

A clogged inlet screen

The screen at the base of the pump keeps stones and grit out of the impeller. When it packs with debris, the pump may start but move little water, or labor and overheat. Unplug the pump, then let it cool for a minimum of 2 hours before you service it. Wayne's warning: "Submersible pumps contain oil that become pressurized and hot under normal operating conditions."^[1] Then lift it out if you can do so without straining the discharge pipe, and clear the screen.

It started, then stopped by itself

Wayne's pump motor has an automatic resetting thermal protector, so it may restart unexpectedly.^[1] Wayne lists what trips it: operating at low heads, excessively high or low voltage, inadequate wiring, incorrect motor conditions, or the end of the product's life.^[1] The same manual says its pumps should not be used for water above 77º F.^[1] Several of those causes are electrical, so have an electrician check the voltage and wiring before you assume the pump is worn out. A pump that has just tripped is hot: unplug it and let it cool before you handle it.

The switch or the motor has failed

If the pump has power, the float moves freely, the screen is clear and there is water in the pit, but the pump still does nothing when you pour water in, a part has failed. In Wayne's chart, for a failed motor the remedy is to replace the pump, and for a failed switch to replace the tether switch or replace the pump.^[1] Wayne's advice: "If the pump doesn’t start, have it serviced or replaced."^[1] See should I repair or replace my sump pump to weigh the two.

If the power is out

A pump with no electricity cannot run at all. Fairfax County's floodproofing guide makes the point: "These pumps almost always run on electricity. During extreme weather, electricity can go out, leaving a basement unprotected against flooding at the time it is needed most."^[3] A battery backup pump covers that gap. If yours has an alarm, Goulds notes that if battery backup operation is due to a power outage, the alarm will sound but the primary pump is not likely to need service.^[2]

Stop and call a pro if

• The GFCI outlet will not reset, or the breaker trips again as soon as the pump starts.
• The lights dim when the pump tries to start, or you suspect low voltage.
• The pump or its switch is hardwired with no plug.
• The pump hums but will not pump after you have cleared the screen, or it smells hot.
• Water is rising in the pit, rain is forecast, and you cannot get the pump running.
• There is water on the floor and the electric panel is in the basement.

For more, see how to test a sump pump, why a sump pump runs constantly and the full list of plumbing repair answers. You can also find licensed plumbers near Blacksburg. When you are ready, describe the problem once and get quotes from licensed plumbers.