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Fix a sump pump that will not run

We'll check power, the float switch, and the impeller—then isolate the cause or tell you when to call a pro.

Troubleshooting · Home plumbing
15–45 min
What you'll need
  • Non-contact voltage tester or lamp (to check outlet)
  • Bucket or hose (to add water to pit for testing)
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Steps

Goal: Confirm the symptom, check power, the float, and the impeller—then isolate the cause.

  • Look into the sump pit. If water is present and the pump does not run, the pump has failed. If the pit is dry, add water manually to test.
  • Good: Water in the pit, pump not running. Proceed to Check power.
  • Bad: Pump runs—different problem.

Check power

Goal: Rule out power loss before testing the pump.

  • Confirm the pump is plugged in. Check that the outlet has power—use a non-contact voltage tester or plug in a lamp.
  • If the outlet is dead, check the GFCI. Sump pumps are often on a GFCI circuit. Check GFCI outlets in the basement, bathroom, or garage for a tripped state. Press reset.
  • Check the circuit breaker panel—reset any tripped breaker for the sump pump circuit.
  • Good: Power at the outlet. Proceed to Check float.
  • Bad: No power—fix wiring or call an electrician.

Check float

Goal: Confirm the float switch triggers the pump when raised.

  • Locate the float switch (a ball or cylinder attached to the pump or discharge pipe). Check that it moves freely and is not tangled or stuck.
  • Manually lift the float—the pump should turn on. If it does not, the switch or wiring may be faulty.
  • If the float is stuck against the pit wall or discharge pipe, free it. Ensure the float cord or rod is not caught.
  • Good: Pump runs when you lift the float—float may have been stuck; free it and test. Bad: Pump does not run when you lift the float—proceed to Check impeller.

Check impeller

Goal: Rule out a blocked or seized impeller.

  • Unplug the pump. Remove the pump from the pit if possible. Inspect the intake screen or impeller for debris. Clear any blockage.
  • Try turning the impeller by hand. If it will not turn, the motor may be seized.
  • Plug the pump back in. Lift the float manually. The pump should run and discharge water.
  • Good: Impeller clear and pump runs. Bad: Impeller seized or pump still does not run—replace pump or call a plumber.

When to get help

Call a plumber if:

  • You are not comfortable with electrical or plumbing.
  • The pump runs but does not move water and the discharge line is clear.
  • The pump is old and replacement is needed.

Verification

  • The pump runs when the pit fills or when you lift the float manually.
  • Water discharges from the pump.
  • The float moves freely and triggers the pump at the correct water level.

Escalation ladder

Work from the device outward. Stop when the problem is fixed.

  1. Confirm symptom Verify the pit has water and the pump does not run.
  2. Power Check outlet, GFCI, and circuit breaker.
  3. Float switch Check that the float moves freely and triggers the pump when raised.
  4. Impeller Check for debris or a stuck impeller. Clear if blocked.
  5. Call a pro Replace pump or call a plumber if the pump still does not run.

What to capture if you need help

Before calling support or posting for help, have these ready. It speeds everything up.

  • Whether power is present at the outlet
  • Whether the float moves freely
  • Whether the pump runs when the float is lifted manually
  • Impeller condition (clear, blocked, seized)
  • Steps already tried

Does the sump pit have water and the pump does not run?

Look into the pit. If water is present and the pump does not run, the pump has failed. Add water manually to test if the pit is dry.

Look into the sump pit. If water is present and the pump does not run, proceed. If dry, add water to test. Good: water present, pump not running. Bad: pump runs—different problem.

Yes No

You can change your answer later.

Is there power at the outlet?

Check that the pump is plugged in. Check GFCI and circuit breaker. Use a voltage tester or plug in a lamp.

Confirm the pump is plugged in. Check the outlet for power. Reset GFCI and circuit breaker if tripped. Good: power present. Bad: no power—fix wiring or call an electrician.

Yes No

You can change your answer later.

Does the pump run when you lift the float manually?

Lift the float. The pump should turn on. If not, the float switch or wiring may be faulty.

Lift the float switch manually. Good: pump runs—float may be stuck; free it and test. Bad: pump does not run—check impeller or replace pump.

Yes No

You can change your answer later.

Free the float and test

Free the float if it was stuck. Ensure it moves freely. Test again. The pump should run when the pit fills. If it runs, the fix is complete.

Done

Is the impeller clear and able to spin?

Unplug the pump. Inspect the intake screen or impeller for debris. Clear any blockage. Try turning the impeller by hand.

Unplug the pump. Inspect the impeller for debris. Clear blockage. Try turning by hand. Good: impeller clear and spins—replug and test. Bad: impeller seized or damaged—replace pump or call a plumber.

Yes No

You can change your answer later.

Test the pump

Plug the pump back in. Lift the float. The pump should run and discharge water. If it runs but does not move water, check the discharge line for blockage.

Done

Call a plumber

Call a plumber if you are not comfortable with electrical or plumbing, if the pump runs but does not move water and the discharge line is clear, or if the pump is old and replacement is needed.

Done

Reviewed by Blackbox Atlas

Frequently asked questions

Why would a sump pump not run?
Power loss (tripped breaker, GFCI, unplugged), a stuck or broken float switch, or a blocked or failed impeller. Check power first, then the float, then the impeller.
How do I check the float switch?
Check that the float moves freely and is not tangled or stuck. Manually lift the float—the pump should turn on. If it does not, the switch or wiring may be faulty.
Can I fix a sump pump that will not run myself?
Yes, for power and float issues. If the impeller is blocked, you can try to clear it. If the motor or impeller has failed, replace the pump or call a plumber.
When should I call a plumber for a sump pump?
If you are not comfortable with electrical or plumbing, if the pump runs but does not move water, or if the pump is old and replacement is needed.

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