The essentials
- Unplug the pump before touching anything in the pit, and never step into water that has reached outlets or the electrical panel.
- The most common culprits are a tripped GFCI outlet, a stuck float switch and a clogged intake screen, all of which many homeowners can fix.
- Lift the float by hand: a click and a running pump mean the switch works, while no click usually means the switch needs replacing.
- If the pump will not run when plugged directly into a working outlet, or sewage is backing up, stop and call a licensed plumber.
- Test the pump each season by pouring a bucket of water into the pit, and keep the pit and intake screen free of debris.
A sump pump rarely fails at a convenient time. It usually quits during a storm, when the pit is filling fast and every minute counts. The good news is that many common causes, from a tripped outlet to a jammed float, can be found and fixed in minutes if you work in a sensible order and know where to stop.
Stay Safe First: Water and Electricity Don’t Mix
Before anything else, deal with electricity. Unplug the pump before your hands go anywhere near the pit, and carry the plug, not the cord.
If standing water has reached wall outlets, or if you would have to wade to reach the pump, do not step in. That is a job for an electrician, not a homeowner in rubber boots.
If sewage has backed up into your home, the EPA advises avoiding contact with it because it can carry harmful pathogens, and it suggests calling your local health department for cleanup guidance. Cleanup personnel are advised to wear protective clothing such as long rubber gloves and face shields. After cleanup, the agency recommends disinfecting exposed areas with a mixture of 90 percent water and 10 percent household bleach, then keeping the area out of use until it has been completely dry for at least 24 hours.
Safety first
Never reach into a sump pit while the pump is plugged in, even to clear a jam. Unplug it first, every time.
Check the Power Supply and GFCI Outlet
Power problems are one of the most common reasons a pump sits silent, so start here. Most sump pumps plug into a GFCI outlet, and GFCI outlets trip easily, sometimes from moisture or a small ground fault in the pump itself.
Work through this list:
- Press the reset button on the outlet and see if it holds.
- Check the breaker panel for a tripped breaker.
- Look over the cord for cracks, cuts or chewed spots.
- Make sure the plug is fully seated; cords get kicked loose more often than people expect.
Many float switches use a piggyback plug, which means the float cord plugs into the wall and the pump cord plugs into the back of it. If yours is set up that way, unplug the pump from the piggyback and plug the pump straight into the outlet. If the motor starts, the pump is fine and the problem is the float switch. If it does not, the trouble is the pump or the power supply.
Look for a Stuck or Jammed Float Switch
The float switch is the buoy that tells the pump when to start and stop. As water rises, the float lifts and trips an internal switch; when the pit drains, the float drops and the pump shuts off. Because floats are mechanical parts living in water and debris, they wear out. A float can wedge between the pump and the pit wall, tangle in its cord, or bind up with sediment.
With the pump plugged back in, lift the float by hand or tilt it the way rising water would. You should hear a click as the switch engages, and the pump should start. No click usually means the switch has failed and needs replacing. If it clicks but the pump stays off, go back to the power checks or plug the pump in directly to test it.
These patterns point to a float problem:
- The pump runs nonstop even when the pit is nearly dry.
- The pump cycles on and off every few minutes.
- The pump never starts even though water is clearly rising.
A pump that runs without water can overheat and destroy its motor, so do not let a stuck float grind away for long. Sometimes the fix is simple: reposition the pump so the float has room to travel, or clear the debris that is binding it. A float positioned too high or too low in the pit can also miss the right water level.
Clear the Pump Intake and the Sump Pit
Unplug the pump, put on gloves and look inside the pit. Gravel, mud and stray objects all find their way in, and large debris can clog the pump itself. Pumps with intake filter screens clog over time as the screen fills, so clean the screen and the intake opening. While you are in there, scoop debris and sediment off the bottom. A pit full of sludge leaves the float and intake less room to work, and regular pit cleaning is one of the maintenance steps that helps prevent float failures. Fine soil or iron ochre in the perimeter drain can clog the system too, leaving the pump little to move.
Trace the Discharge Line and Check Valve
If the pump runs but the pit keeps refilling with the same water, look up. On the vertical pipe above the pump sits a check valve, a one-way flap that lets water out but snaps shut when the motor stops so gravity cannot pull it back down. If that flap breaks or hangs open, discharged water falls right back into the pit, the float triggers again, and the pump runs in an endless loop.
The discharge line, the pipe that carries water away from the house, can clog with dirt, roots or ice, which backs water up into the pit. Walk the line outside if you can see it and check where it empties. Water dumping beside the foundation will find its way back.
| What you see | Likely cause | What to try |
|---|---|---|
| Pump silent while water rises | Power or float switch | Reset the outlet, check the breaker, lift the float |
| Runs nonstop with a dry pit | Stuck or failed float | Free the float, clean the pit, replace the switch if needed |
| Pump runs but the pit refills | Failed check valve or clogged line | Inspect the valve, check the discharge line outside |
| No click when you lift the float | Failed float switch | Replace the switch or call a plumber |
When to Stop and Call a Licensed Plumber
Some of the fixes above are homeowner work. Others are not. Call a licensed plumber if the pump will not run even when plugged straight into a working outlet, if it trips the GFCI again and again, or if it needs replacing and you would rather not do it yourself. A worn-out pump is not something to nurse along. One industry estimate put a replacement pump between $200 and $400 as of 2026, small money next to repairs for a flooded basement.
Get help right away if water is rising faster than you can manage, if sewage is backing up into fixtures, or if you suspect the problem is your septic system rather than the pump. A septic tank that has gone years without pumping can let solids migrate into the drain field and clog the system, which can look like ordinary plumbing trouble from inside the house.
How to Prevent the Next Failure
Most sump pump failures build up quietly, and a little routine attention catches them early:
- Test the pump every season by pouring a bucket of water into the pit and watching it start, lower the water and shut off. One step checks the float, the motor and the check valve.
- Clean the pit and the intake screen whenever debris or sediment builds up.
- Keep the float free to move, and check that it is not wedged or tangled after any work near the pit.
- Consider redundancy. Contractors who specialize in basement waterproofing often recommend a primary pump, a secondary pump and a battery backup, so one failure or a power outage does not leave the pit unprotected. Submersible cast-iron pumps are often chosen because they hold up well over time.
- Fold the pump into your seasonal routines alongside other water-using equipment, as our water heater care timeline shows.
A pump that gets a few minutes of attention each season is far less likely to quit during the storm that matters.
Related guides
- A Fall Home Maintenance Checklist: a seasonal routine for catching small home problems before they turn into emergencies.
- A Timeline for Water Heater Care: a maintenance schedule for another hard-working appliance that is easy to forget.
Common questions
Why does my sump pump run but the pit keeps refilling?
A failed check valve on the discharge pipe can let pumped water fall back into the pit, so the pump runs in an endless loop. A clogged discharge line can back water up the same way.
How do I test the float switch?
With the pump plugged in, lift the float by hand the way rising water would. A click and a running pump mean the switch engages; if it clicks but the pump stays off, test the pump plugged in directly, and if there is no click, the switch likely needs replacing.
Can I replace a float switch myself?
Many float switches use a piggyback plug, which makes them a straightforward swap for a comfortable DIYer. If the pump itself will not run when plugged straight into a working outlet, call a licensed plumber instead.
How often should I test my sump pump?
A seasonal test works well for most homes. Pour a bucket of water into the pit and confirm the pump starts, lowers the water and shuts off cleanly.
This guide is general information, not professional advice. Follow the manufacturer’s instructions and your local building codes, and hire a licensed professional for electrical, gas, structural or roofing work.