Sump Pump Not Pumping Water? Causes and Quick Fixes

A sump pump that will not move water is a real problem when rain is on the way. There are two cases: the pump runs but no water comes out, or the pump will not turn on at all. Each has a short list of likely causes. Work through them and you can usually get water moving again fast.

Here is how to diagnose both, and when it is time for a new pump from the sump pumps collection.

Case 1: The Pump Runs but No Water Comes Out

If you hear the pump humming or running but the pit is not draining, the likely causes are:

• An airlock, where trapped air stops the pump from moving water
• A clogged intake or impeller, jammed with debris
• A stuck impeller, seized after sitting unused
• A frozen or blocked discharge line, common in winter
• A failed check valve, letting water flow back into the pit

How to Clear an Airlock

Airlock is one of the most common causes. Many pumps have a small weep hole, or air-relief hole, in the discharge pipe just above the pump that lets trapped air escape. If it is missing or clogged, the pump can airlock. With the power off, check that the weep hole is clear, and confirm the discharge line is not blocked or frozen.

Case 2: The Pump Will Not Turn On

If the pump is silent, work through power and controls:

• Check the power, the outlet, breaker, and GFCI
• Check the float switch, which may be stuck or failed (browse float switches)
• Test the switch directly by lifting the float; if the pump runs, the switch is the problem
• If there is power and the float works but the motor is dead, the pump has likely failed

Repair or Replace?

A stuck float, a clogged intake, or an airlock are quick fixes. But if the motor is dead, the pump is old, or it has failed you during a storm before, replacement is the safer bet. A quality submersible pump with a dependable float and a backup is cheap insurance against a flooded basement. Our basement sump pump buyer's guide covers sizing and backups.

Final Thoughts

Split the problem in two: running but not pumping usually means an airlock, clog, or bad check valve; not turning on usually means power or the float. Clear the simple issues fast, and if the pump is dead or unreliable, replace it before the next storm.

Frequently Asked Questions

Why is my sump pump running but not pumping water?

The usual causes are an airlock, a clogged intake or impeller, a frozen or blocked discharge line, or a failed check valve letting water drain back. Check the weep hole and discharge line first.

What is an airlock and how do I fix it?

An airlock is trapped air that stops the pump from moving water. Most pumps have a small weep hole in the discharge pipe to release it. With the power off, make sure that hole is clear and the discharge is not blocked.

Why won't my sump pump turn on?

Check the power (outlet, breaker, GFCI) and the float switch, which may be stuck or failed. Lift the float to test; if the pump runs, the switch is the issue. A dead motor with good power means the pump has failed.

Should I repair or replace my sump pump?

Fix simple issues like a stuck float or a clog. If the motor is dead, the pump is old, or it has failed during a storm before, replace it, ideally with a backup, to protect your basement.