Sump Pump Not Working: What to Check First

Updated November 12, 2026 · 6 min read

Safety before anything else

A sump pit is a small pool of water with electricity in it. Before you reach into it:

• Unplug the pump at the outlet with dry hands. If the outlet or cord is wet or you are standing in water, stop and call an electrician.
• Never put a hand in the pit while the pump is plugged in.
• Wear gloves. Pit water is often dirty and can carry bacteria.
• If water is near the furnace, panel or outlets, leave the basement alone and shut off power at the main breaker only if you can reach it from a dry spot.

The checks, in order

1. Power

Look at the outlet first. Is the plug seated? Has a breaker tripped? Try a lamp or a phone charger in the same outlet to confirm there is power. Many pump outlets share a circuit with other basement outlets, so a breaker that tripped for another reason can take the pump with it.

2. GFCI

A tripped GFCI looks exactly like a dead pump. Press the reset button on the outlet, or on the first outlet in the circuit. If it trips again right away, something is wrong with the pump, the cord or the wiring. Do not keep resetting it in a storm. That is a job for an electrician.

3. Float switch

The float tells the pump when to start. Pour a few buckets of water into the pit, or lift the float by hand while the pump is plugged in and your hands are dry. If the pump starts when you lift it but not when the pit fills, the float is stuck. Common causes:

• It is wedged against the side of the pit
• It is caught on its own cord
• It is coated with grease, silt or mineral scale
• The pump is sitting in a pit too narrow for the float to swing

Reposition it, clean it and test again. A float that works by hand but fails in water may need replacing.

4. Debris in the pit

Silt, gravel and sometimes small stones collect in the bottom. They block the intake and wear the impeller. Unplug the pump, lift it out if you can, and scoop the pit clean. Clean the screen at the base of the pump.

5. Check valve

The check valve is a one-way valve on the discharge pipe that keeps pumped water from running back into the pit. Signs of trouble are a pump that cycles over and over, a rush of water falling back into the pit after each run, or a pump that seems to run but never lowers the water level. Look for the arrow on the valve body, which should point away from the pump. Replacing a stuck valve is simple for a handy homeowner and quick for a plumber.

6. Discharge line

Follow the pipe from the pump out of the house and to where it ends. In Spokane winters, the end of a discharge line can freeze solid, especially when it sits on the ground or has a low spot where water pools. The pump then pushes against ice and trips its thermal protection, or it hums without moving water.

What to check:

• Is the outlet end buried in snow or capped with ice?
• Does the pipe sag, holding water that can freeze?
• Does the line end close to the house, so water returns to the foundation?
• Is there a loose coupling or a crack where a section has pulled apart?

Clear the end gently. A pipe that slopes down and away, ends in open air, and has a grated or flap-style outlet is much less likely to freeze up. Never use an open flame to thaw it. Warm water poured on the ice is safer. Do not pour boiling water on a plastic pipe.

7. The pump itself

If everything above checks out and the pump still will not run or hums without moving water, the motor or impeller may have failed. Age matters here. A pump that is a decade old and noisy is a candidate for replacement. A plumber can size and install a new one in a short visit.

Battery backups and other protection

A primary pump relies on household power, and power tends to fail when storms and snow load bring down lines. A battery backup pump sits beside the main pump in the pit and runs when the main one stops or when the power is out. Water-powered backups use water pressure from your supply and need no battery, but they depend on municipal pressure and are not for use with a private well.

Whichever you choose:

• Test it twice a year by raising the float or filling the pit with water
• Replace the battery when it is old, because a dead backup does nothing
• Add a high-water alarm that sounds before the pit overflows
• Put the pump on its own labeled circuit when possible

None of these is a promise against flooding. They give you time. Our post on spring snowmelt and basement flooding covers the pre-thaw routine and the other ways water finds a basement.

If the basement is already wet

Water on the floor is a different problem from a dead pump. Do these in order:

1. Stay out until power to the area is safe.
2. Find where the water is coming from. Is it from the pit, a window well, a crack or the floor drain?
3. Lift anything valuable off the floor and take photos of the water line.
4. If there is only a thin layer, a wet vacuum can handle it. Deeper water needs a pump and should come out gradually.
5. Call a local crew. They will pump out the water, check the walls and flooring with moisture meters, and set drying equipment.

Pit overflow and groundwater are not the same thing as a sewer backup. If the water smells like sewage or came up through a floor drain, treat it as contaminated and read our guide on what to do after a sewage backup. For clean groundwater that spread across the floor, emergency water extraction is the first step, and the basement flooding page explains the drying that follows.

Insurance notes

A sump pump failure is not always covered. Many standard policies exclude water that backs up or overflows from a sump unless you carry a specific endorsement, and groundwater coming through walls usually needs flood coverage. Read the wording before the next storm and ask your agent what limit applies.

What the cleanup depends on

Cost follows the same factors as any basement flood: how deep the water got, how long it sat, whether the space is finished and whether the source was clean. The company that inspects gives a written figure before work starts. See the basement flood cleanup cost guide for the breakdown.

A yearly routine

• Pour water into the pit each spring and fall and watch the cycle
• Clear the pit and the intake screen
• Walk the discharge line and confirm the outlet is open and drains away from the house
• Test the battery backup and the alarm
• Make a note of the pump's age and plan its replacement

Sources and official resources

• Verify a Washington contractor (Washington L&I)
• Home insurance guide (Washington Insurance Commissioner)
• IICRC: restoration industry standards body
• Flood insurance basics (FEMA FloodSmart)
• A Brief Guide to Mold, Moisture and Your Home (EPA)