Sump Pump Not Working — Troubleshooting

A sump pump usually fails in one of three ways — it won’t run, it runs and won’t stop, or it runs but no water leaves the pit — and each points to a short list of causes: lost power, a stuck float, a clogged intake or check valve, or a frozen or blocked discharge. The good news is that most of these are things you can check yourself, in order, before concluding the pump is dead. Work the list methodically and you’ll often find the fix is a tripped outlet or a snagged float, not a new pump.

If you want to understand what each part is doing while you troubleshoot, keep how a sump pump works open alongside this.

First, deal with the power safely

Before any hands-in work, handle the electricity.

Symptom 1: the pump won’t run at all

A silent pump is most often a power problem or a stuck float — not a failed motor.

Check power first. Confirm the pump is actually plugged in (cords get bumped loose), that the outlet has power, and that no breaker has tripped. Pay special attention to the GFCI: if the pump is on a GFCI outlet that has tripped, it gets no power while everything else looks normal. Reset it once. If it trips again immediately, stop resetting and get an electrician — repeated tripping is a warning, not a nuisance.

Then check the float. If power is fine, the next suspect is the float switch. It can wedge against the pit wall, snag on its own cord, or jam against silt and debris so it can’t rise. With the pump unplugged, confirm the float moves freely through its full range. A float that can’t lift never tells the pump to start.

Symptom 2: the pump runs constantly

A pump that never shuts off is either being told to run when it shouldn’t, or re-pumping the same water.

• Stuck float, held up. The mirror image of symptom 1 — a float jammed in the raised position keeps the switch closed and the motor running. Free it and confirm it drops.
• Failed check valve. This is a classic. If the check valve on the discharge pipe fails, water that was just pumped up the pipe drains back into the pit the moment the pump stops, so the pump immediately restarts to re-pump it. Rapid on-off short-cycling points straight at the check valve.
• Pit too small. If the pit can’t hold enough water between cycles, the pump kicks on constantly during heavy inflow. This is more of a sizing issue than a fault.
• High water table. Sometimes the pump is running constantly because there genuinely is that much groundwater. That’s a drainage question, not a pump defect — the pump is doing its job against more water than it should have to.

If you’d like context on why so much water is arriving at once, why a basement gets wet after rain covers where it’s coming from.

Symptom 3: the pump runs but moves no water

Here the motor is alive — you hear it hum or run — but the pit doesn’t empty. Water isn’t reaching the impeller, or it has nowhere to go.

• Clogged intake. Silt, gravel, or debris blocking the intake screen starves the pump. Unplug it and clear the intake.
• Air lock. Trapped air can stop a pump from moving water even while the motor runs. Some pumps have a small weep hole to prevent this; a clogged one can cause it.
• Stuck check valve. A check valve stuck closed blocks the water’s path out entirely.
• Frozen or blocked discharge. If the discharge line is frozen or obstructed, the water has nowhere to go, so the pit stays full no matter how hard the pump works.

Symptom 4: the discharge line is frozen or blocked

Because this one masquerades as several other failures, it’s worth calling out on its own. A frozen or clogged discharge makes a good pump look dead: the pit won’t empty, the motor may strain, and you’ll swear the pump has failed. Walk the line end to end — inside for kinks or crushed sections, outside for the buried, crushed, or iced-over outlet. Restoring the path out often restores the whole system with no pump repair at all.

Symptom-to-cause table

Symptom	Likely cause	Safe check (pump unplugged for hands-in steps)
Won’t run at all	No power / tripped GFCI or breaker	Confirm plug, outlet, breaker; reset GFCI once
Won’t run at all	Stuck float (can’t rise)	Free the float; confirm full range of motion
Runs constantly	Stuck float (held up)	Free the float; confirm it drops
Runs constantly	Failed check valve (short-cycling)	Look for backflow and rapid restart after shutoff
Runs constantly	Pit too small / high water table	Assess inflow vs. pit size; a drainage question
Runs, no water	Clogged intake	Unplug; clear the intake screen
Runs, no water	Stuck check valve or air lock	Check valve movement and any weep hole
Runs, no water	Frozen or blocked discharge	Walk the line; clear the outlet, check for ice

When to call a pro

Some of this is squarely a homeowner’s to handle: checking power, resetting a GFCI once, freeing a float, clearing the intake, walking the discharge. Bring in a professional when the checks come up empty and the pump still won’t perform, or when the trouble is electrical. Specifically, call a licensed electrician if a breaker or GFCI keeps tripping, if the pump needs hardwiring or a dedicated circuit, or if you smell burning or see scorching. Repeated tripping is a signal to stop resetting and get help. A licensed plumber is the right call for reworking a discharge that has to meet local code. Guessing at wiring next to standing water isn’t a savings — it’s a hazard.

Common mistakes

• Assuming the pump is dead too soon. Replacing a pump that was only unplugged, tripped at the GFCI, or held up by a stuck float.
• Reaching in while it’s plugged in. Turning a two-minute float check into a shock risk by skipping the unplug step.
• Resetting a tripping GFCI over and over. Treating repeated trips as a nuisance instead of the electrical warning they are.
• Blaming the motor for short-cycling. Overlooking a failed check valve sending water right back to the pit.
• Missing the frozen discharge. Diagnosing a “dead” pump that’s actually fine — the water just has nowhere to go.
• Ignoring why the pit fills so fast. Fixing the pump while grading and downspouts keep feeding water at the foundation.

Most sump pump failures aren’t the pump. Work power, float, intake, check valve, and discharge in order, keep the thing unplugged whenever your hands are in the pit, and you’ll usually find the culprit — and know when it’s time to hand it to a licensed pro.