Sump Pump Failure: Warning Signs, Fixes and Backup Options

A sump pump is an electric pump that sits in a pit at the lowest point of a basement or crawl space and pushes groundwater out and away from the house before it can rise over the floor. When a sump pump fails, it is usually because the power went out, the float switch stuck, the pump wore out, the discharge line clogged or froze, or more water came in than the pump could move. Most failures can be caught early with a simple test a few times a year, and a battery or water-powered backup covers the most common cause: a power outage during a storm.

What is a sump pump and how does it work?

Groundwater collects in the sump pit through drain tile around the foundation or through the gravel under the slab. As the water rises, it lifts a float. When the float reaches a set level, it switches the pump on. The pump pushes water up a discharge pipe and outside, and a check valve on that pipe keeps the water from falling back into the pit. When the level drops, the float switches the pump off.

FEMA describes sump pumps as a way to "propel groundwater away from your home" and an important defense against basement seepage and flooding.

Submersible vs. pedestal sump pumps

NDSU Extension engineers note that on a pedestal pump the motor sits about a foot above the top of the sump. Either type works when it is sized and maintained properly. NDSU Extension's sump pump FAQ says a 1/3 hp sump pump is satisfactory for most houses, but the right size depends on how much water flows into your pit and how high the pump has to lift it, so match a replacement to what your current pump handles.

Sump pump failure: common causes

Consumer Reports lists the main reasons a primary pump stops protecting a basement as a power failure, a mechanical breakdown, or an overwhelming amount of water, along with age and lack of maintenance. In more detail:

1. Power outage. Storms that bring heavy rain often knock out power, which stops a plug-in pump right when it is needed most.
2. Stuck or failed float switch. Debris, a tangled cord or a pump that has shifted against the pit wall can hold the float down or up. NDSU Extension lists a float switch that does not make good electrical contact as a common failure.
3. Worn motor or bearings. NDSU also names damaged or rusted motor bearings as a common failure. A grinding or gravel-like sound is a warning.
4. Clogged intake or impeller. Silt, gravel and debris in the pit can block the screen.
5. Blocked or frozen discharge line. If water cannot leave the pipe, the pump runs but nothing moves.
6. Failed check valve. Water drains back into the pit after each cycle, so the pump cycles more often and wears out faster.
7. Undersized pump. In a very wet season, inflow can exceed what the pump can move.
8. Old age. Family Handyman puts typical sump pump life at seven to 10 years, sometimes longer with maintenance.

Warning signs your sump pump is failing

• It runs constantly or for a long time without emptying the pit.
• It cycles on and off rapidly, a sign of a bad check valve, a float problem or a mismatched pump size.
• It makes new noises: grinding, rattling or heavy vibration.
• It runs but moves little water, pointing to a blocked intake or discharge.
• It does not start when water rises in the pit.
• Visible rust on the casing of a submersible pump.
• The battery backup alarm sounds, meaning the primary pump is not keeping up.

How to fix a sump pump that stopped working

Unplug the pump before you reach into the pit, and do not work in standing water if there is any chance of electric shock.

1. Check power first. Make sure the pump is plugged in and the breaker or outlet has not tripped. A tripped circuit can look like a dead pump.
2. Free the float. Remove the lid, look in with a flashlight, and clear anything snagging the float or cord. Make sure the pump is level and not leaning against the pit wall.
3. Clean the intake screen. Lift the pump out and clear silt and debris from the screen and the bottom of the pit.
4. Check the discharge line. Follow it outside. Clear ice, dirt or leaves from the end, and make sure it is not crushed or disconnected.
5. Test the check valve. After the pump shuts off, listen for water rushing back into the pit. If it does, the valve may be stuck open.
6. Run a water test (below).

If the motor hums but does not pump, or the pump still fails the test, it likely needs replacement. If the basement is already flooding, call a plumber for the pump and see what to do after water damage for the cleanup.

How to test a sump pump (sump pump maintenance)

NDSU Extension recommends this routine, ideally before spring thaw and before heavy rain seasons:

1. Confirm the outside discharge pipe is clear and sends water away from the house.
2. Confirm the pump is plugged in and the pit is free of debris.
3. Lift the float for about 10 seconds to see that the pump starts and runs smoothly, then lower it slowly.
4. Pour water into the pit at about the rate water normally flows in, and make sure the pump turns on and off at least twice.
5. Test a backup pump the same way.

Consumer Reports adds a few routine checks: clean battery terminals, top off water in flooded lead-acid batteries, clear debris from the pit, and a few times a year unplug the main pump, fill the pit and confirm the backup runs.

Sump pump battery backup and other backup options

A backup protects against the failure that tends to strike during storms: losing power. FEMA recommends choosing a battery-operated sump pump in case the power goes out, and FloodSmart's homeowner tips say installing a battery backup can keep it working when the power goes out.

Backup batteries wear out sooner than pumps. Consumer Reports says AGM batteries last up to about seven years and flooded lead-acid batteries about three to five. Most backup systems include an alarm, and some Wi-Fi models send phone alerts.

Sump pump cost: replacement and installation

Costs depend on the pump type, whether a pit already exists, and how the discharge line runs. This Old House, using Fixr and Angi data, lists a national average sump pump installation cost of $1,400, with a typical range of $500 to $4,000, and replacing a pump in an existing basin at $350 to $1,000 (updated March 2026). The biggest cost drivers:

• New pit vs. existing basin. Cutting through a concrete floor and digging a pit adds the most.
• Discharge piping. Buried lines cost more than above-ground runs.
• Backup system. Battery, water-powered or combination units add equipment and labor.
• Electrical work. A dedicated outlet may be needed near the pit.

Does insurance cover sump pump failure?

Usually not under a standard homeowners policy alone. Water that backs up or overflows from a sump is typically covered only if you add a water backup or sewer backup endorsement, which the Insurance Information Institute says is usually available for a small added cost. Flood damage is excluded from homeowners policies and needs separate flood insurance. Under an NFIP flood policy, FloodSmart lists sump pumps as covered basement equipment when installed and connected to power. Read your policy, and see our guide to water damage insurance claims.

If your basement already flooded

Turn off power to the basement if you can do so safely, document the damage with photos, and start drying quickly. EPA says that drying wet materials within 24 to 48 hours prevents mold in most cases. Our flooded basement cleanup guide covers the steps, and why basements flood after rain covers prevention beyond the pump. Damp basements are also prone to basement mold.

Flood Rescue Pros is a free service that connects homeowners with independent local water damage restoration companies. Get help now or find local service areas. For extraction and structural drying, see flooded basement cleanup.

Frequently asked questions

What is the purpose of a sump pump?

A sump pump removes groundwater that collects in a pit below the basement floor and sends it outside, so the water table around the foundation does not rise into the basement.

How long will my sump pump last?

Family Handyman puts typical life at seven to 10 years, and longer with maintenance. Pumps that run often wear out faster, so test yours a few times a year and watch for warning signs.

Should I buy a house with a sump pump?

A sump pump tells you the site has groundwater to manage, not that the house is bad. Ask how often it runs, its age, whether it has a backup, and whether the basement has ever flooded, and have it inspected.

Can I install a sump pump myself?

Replacing a pump in an existing pit is a common do-it-yourself job if you follow the manufacturer's instructions. Digging a new pit through concrete, adding drainage or wiring a new circuit is usually work for a plumber or contractor.

Why does my sump pump run when it is not raining?

High groundwater, snowmelt or a leaking check valve can keep water flowing into the pit. If it cycles every few minutes in dry weather, check the check valve and look for a plumbing leak.

Key facts

• A sump pump moves groundwater from a pit under the basement floor to the outside; a float switch turns it on and off.
• The main failure causes are power loss, mechanical breakdown and more water than the pump can handle (Consumer Reports).
• Test it by pouring water into the pit and confirming it turns on and off at least twice (NDSU Extension).
• A battery backup runs about 7 to 8 hours of active pumping on a full charge; batteries last roughly 3 to 7 years depending on type.
• Typical sump pump life is about 7 to 10 years (Family Handyman).
• Standard homeowners policies usually need a water backup endorsement to cover sump overflow.