Sump pump not working: check these in order
- Power. The pump is usually plugged into an outlet near the pit, often a GFCI that trips. Check the outlet and the breaker.
- The float. A float that rubs against the pit wall or the pump body can stick in the down position. Lift it by hand; if the pump starts, the switch works and the float needs space.
- The switch itself. If lifting the float does nothing and the pump has power, the switch has failed. On many pumps it can be replaced separately.
- The motor. A pump that hums but doesn't pump may be jammed with debris at the intake or have a seized motor.
Running constantly or cycling too often
A pump that never stops may have a float stuck in the up position, or it may simply be facing more water than it can move. A pump that starts every minute or two, even in dry weather, often has a failed check valve: the water in the discharge pipe falls back into the pit each time the pump stops, and the pump lifts it again. A pit that is too small for the pump creates the same short cycling. Both wear out motors.
Discharge line problems
The discharge pipe carries water from the pit, through the check valve, and outside. In cold climates, the outdoor section can freeze and block the flow completely; a pump running against a frozen line burns out. Many installations add a freeze-protection fitting that lets water escape near the house if the line beyond it is blocked. Outdoors, the water should exit well away from the foundation, or it cycles straight back into the pit.
Repair or replace: typical costs
| Item | National range |
|---|---|
| Sump pump installation (average $1,400) | $800–$2,000 |
| Pedestal pump, material | $80–$800 |
| Submersible pump, material | $90–$1,000 |
| Battery backup added to an existing pump | $150–$250 |
| Water-powered backup pump | $200–$900 |
| Combination electric and water-powered pump | $500–$1,500 |
Source: Fixr, Sump Pump Installation Cost, updated January 31, 2025. The low end reflects a pedestal pump in an existing pit; the high end a new pit with two pumps and backup.
Pedestal pumps keep the motor above the pit and are easier to service; submersible pumps sit in the water, run quieter and handle more flow. When a pump of either kind has failed after years of service, replacing it is usually more sensible than repairing the motor.
Backup pumps
A primary pump fails most often during the storms it exists for, sometimes because the power goes out. A battery backup pump runs from a charged battery during an outage. A water-powered backup uses municipal water pressure to drive a venturi and needs no electricity, though it uses city water to do it and some jurisdictions restrict it or require backflow protection for it. A high-water alarm is the inexpensive minimum for any pit.
This page is about the pump
Fixing the pump is plumbing. Drying out a basement that has already flooded is a different trade with different contractors, and we don't cover it here. For the other fixtures a plumber maintains, see our plumbing fixture repair guide, and if water is coming up through a floor drain rather than into the pit, the main line clog page is the right one.
Sump pump questions
How do I test a sump pump?
Pour a bucket of water slowly into the pit until the float rises. The pump should start, empty the pit to below the float’s off point and stop. Listen for the check valve closing and look for water leaving the discharge outside.
Why does the pump run but not empty the pit?
The discharge line may be frozen or clogged, the check valve may be stuck, or the impeller may be worn or blocked. Some pumps have a small relief hole that clogs and air-locks the pump.
Can the sump pump drain into the sewer?
Many cities prohibit connecting sump pumps to the sanitary sewer, because the clean groundwater overloads treatment plants during storms. Discharge usually goes outdoors, away from the foundation, or to a storm drain where allowed.
Is a battery backup worth it?
If the basement stays dry only because the pump runs during storms, yes: storms cut power when the pump is needed most. Fixr lists $150 to $250 to add a battery backup to an existing pump.
Sources
- Sump Pump Installation Cost, Fixr, updated January 31, 2025.
Reviewed September 27, 2026. Found an error? Write to admin@plumbingrepairquotes.com.