Why is my sump pump not turning on?
The pit is full or rising and the pump stays silent, or it hums without moving water.
This one can get worse fast. Call before it spreads.
Key takeaways
- This is an emergency. Shut things down and call a plumber now rather than waiting.
- Most likely cause: Stuck or obstructed float switch.
- Do this first: Confirm the pump is plugged in and reset the GFCI or breaker once.
- Call right away if the pit is overflowing or water is reaching the basement floor.
- The repair starts with: Verify power and test the float with a controlled fill.
What it is
Sump pump not turning on A sump pump not turning on means the pit is filling or full of water while the pump stays silent, usually from a failed float switch, a lost power supply, or a seized or burned out motor.
This needs immediate action during wet weather, since a pump that will not run leaves the basement with no protection against flooding.
The short answer
A sump pump that will not start is usually a power problem or a stuck float switch. Check that the pump is plugged in and the breaker has not tripped, then look at the float. If it is wedged against the pit wall or tangled on the discharge pipe, it can never rise far enough to trigger the pump. If power and float both check out and the pit is filling, the motor or the impeller has failed and the pump needs replacing before the water reaches the floor.
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What it usually means
These are the causes we find most often, ranked from most likely to least.
- 1
Stuck or obstructed float switch
Most likely
The float catches on the pit wall, the pipe, or debris and never triggers.
- 2
No power to the pump
Common
Unplugged cord, tripped GFCI, or a tripped breaker after a storm.
- 3
Clogged intake or impeller
Common
Silt and gravel jam the impeller so the motor hums without pumping.
- 4
Frozen or blocked discharge line
Less common
Common in Denver winters when the exterior discharge ices over.
- 5
Failed motor at end of life
Occasional
Most pumps run seven to ten years before replacement.
What to do right now
- 1Confirm the pump is plugged in and reset the GFCI or breaker once.
- 2Pour a bucket of water into the pit and watch whether the float rises and triggers the pump.
- 3Free the float if it is caught on the pit wall or the discharge pipe.
- 4Check the exterior discharge point for ice or blockage.
When it is an emergency
- The pit is overflowing or water is reaching the basement floor.
- Heavy rain or snowmelt is forecast and the pump is not working.
- There is standing water near electrical equipment.
What the fix involves
A stuck float or a blocked intake is a service call. A failed motor is a replacement, and that is the right time to confirm the discharge line is properly pitched and freeze resistant, and to discuss a battery backup for storm outages.
- 1Verify power and test the float with a controlled fill.
- 2Clear the intake screen and the impeller.
- 3Clear or reroute a blocked or freezing discharge line.
- 4Replace the pump and check the check valve and discharge pitch.
What drives the cost
Every job is quoted before work begins. These are the factors that move the number on this kind of repair.
- Service and clearing versus full pump replacement
- Pump capacity and whether a backup system is added
- Discharge line rework
- Emergency response during a storm event
Related problems homeowners ask about
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Toilets, tubs, and floor drains back up together, water rises in the lowest fixture when an upstairs one is used, and drains gurgle across the house.
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A faucet that trickles or gives nothing during a cold snap, frost on exposed pipe, or bulged pipe in a crawlspace or exterior wall.
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Dark water or waste rising in a shower pan or tub, often when a toilet is flushed or a washing machine drains.
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- Colorado Master PlumberLicense MP-18927
- Colorado State Plumbing ContractorLicense 2110
- Family Owned & OperatedServing Denver since 2006, 20 years
- Better Business BureauAccredited Business, A+ rating
- Angie's List Super Service Award2012 through 2017
- Serving Denver since 2006Residential and commercial properties across the metro
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