How to Fix a Sump Pump That Won't Turn Off: Step-by-Step Guide

A sump pump that will not shut off is a warning that something has failed — and a pump running around the clock will burn out its motor, often at the worst possible time during a heavy rain.

A sump pump that will not shut off is a warning that something has failed — and a pump running around the clock will burn out its motor, often at the worst possible time during a heavy rain. Diagnosing the cause is straightforward if you work through the most common reasons systematically.

The Four Most Common Causes

1. Float switch stuck in the on position — the float cannot drop to shut the pump off
2. Failed check valve — water drains back into the pit and retriggered the float
3. High groundwater table — water is continuously entering the pit faster than the pump can clear it
4. Undersized pump — the pump cannot keep up with inflow volume

What You Will Need

• Flashlight
• Adjustable pliers or channel-lock pliers
• Bucket and old towels
• Replacement float switch — if the float is damaged
• Sump pump check valve — if the existing one has failed
• PVC pipe primer and cement — for check valve installation
• Replacement sump pump — if the pump itself is the undersized root cause

Step 1: Check the Float Switch

Unplug the pump before reaching into the pit.

Shine a flashlight into the pit and observe the float position and movement. Manually lift the float arm or tethered ball through its full range — from the lowest position where it rests when the pit is empty, to the elevated position where it would trigger the pump.

Signs of a stuck or failed float:

• The float is tangled around the discharge pipe or pump housing and cannot drop freely
• The float body feels heavy when lifted — it has filled with water through a crack or seam failure
• The float arm moves freely but the pump runs regardless (the switch contacts are welded closed)
• The float is jammed against the pit wall

If the float is tangled, reposition it so it has a clear arc to move through. If the float is waterlogged or the switch contacts have failed, replace the float switch — this is a $20 to $40 part.

Step 2: Test the Check Valve

A failed check valve is the second most common cause of a pump that will not shut off.

Locate the check valve — it is the device installed vertically in the discharge pipe above the pump. It should have an arrow indicating flow direction (pointing up, toward the discharge).

Test it: After the pump shuts off, put your ear near the check valve. You should not hear water flowing back through it. If water is audibly or visibly running back down the discharge pipe each time the pump stops, the check valve is not seating.

Replace the check valve:

1. Unplug the pump.
2. Cut out the old check valve from the discharge pipe using a hacksaw or PVC cutter, leaving enough pipe stub on each side to fit a new valve.
3. Dry-fit the new check valve, confirming the arrow points away from the pump (upward).
4. Solvent-weld with PVC primer and cement or use a slip-joint union-style valve that does not require gluing.
5. Allow the cement to cure fully before restoring power.

Step 3: Assess the Water Inflow Rate

If the float switch and check valve are both working correctly, the problem may be that water is entering the pit faster than the pump can discharge it.

Measure the inflow rate:

1. Unplug the pump and wait until the pit fills to the float activation level.
2. Time how long it takes for the pit to rise 1 inch with the pump off.
3. Plug the pump back in and time how long it takes to drop 1 inch with the pump running.

If the pit fills faster than the pump can empty it, you have an inflow rate problem. Consider:

• Upgrading to a higher-capacity pump (1/2 or 3/4 horsepower)
• Adding a second pump to the pit
• Addressing the source of water entry (French drain improvements, exterior waterproofing)

Step 4: Inspect the Discharge Line for Blockage

A partial blockage in the discharge line forces the pump to run longer to move the same volume of water and increases the risk of the pump never fully keeping up.

Disconnect the discharge line at the exterior exit point and check for:

• Dirt or debris accumulation
• A discharge outlet that is frozen or buried under soil
• A buried pipe end that has become clogged with sediment

Clear any blockage and confirm water flows freely through the full discharge run.

Step 5: Replace the Pump if It Is Undersized or Worn

A pump more than 7 years old that runs constantly may simply be wearing out — impeller wear, motor winding degradation, and seal failures reduce effective pumping capacity over time.

If the pump checks out mechanically but cannot keep up with inflow that it previously handled, replacement is the most reliable solution. Choose a pump rated for at least 2,000 gallons per hour at a 10-foot head for standard residential use, or 3,000 gallons per hour or more for high-water-table situations.

After installing a new pump, add a battery backup sump pump in the same pit as insurance against power outages during heavy rain events.

Related Guides

• How to Fix a Broken Sump Pump Float
• How to Install a Sump Pump
• How to Fix a Flooded Basement After Rain
• How to Fix a Leaking Basement Sump Pit
• Best Portable Generators for Home Backup — keep your sump pump running when power goes out during a storm