Sump pump not working? Here's what to check first
Quick answer
A sump pump not working usually comes down to one of four things: a stuck or tangled float switch, a tripped GFCI outlet or circuit breaker, a failed pump motor, or a clogged intake screen. Start at the outlet — plug something else in to confirm power. Then check whether the float can move freely. If the pump hums but doesn't move water, the impeller is likely jammed or the motor is burned out. Most float and power fixes are DIY-friendly; a motor failure or persistent flooding situation calls for a licensed plumber or pump specialist.
Common causes
- Stuck or tangled float switch — the most common culprit. The float gets wedged against the pit wall or the pump body and can't rise to trigger the pump.
- Tripped GFCI outlet or circuit breaker — sump pumps are almost always on a dedicated GFCI circuit; a surge or moisture hit can trip it silently.
- Failed pump motor — motors burn out from age, running dry, or overheating. If you hear a hum but no water moves, the motor or impeller is likely the problem.
- Clogged intake screen or impeller — debris from the pit jams the screen or the spinning impeller, starving the pump of flow.
- Pump sized wrong for the pit or inflow rate — an undersized pump runs continuously, overheats, and fails early; an oversized one short-cycles.
- Discharge line frozen or blocked — in winter, a frozen or clogged outlet pipe creates back-pressure and the pump shuts off on its thermal overload.
What to check first
- Check the outlet first — unplug the pump and plug in a lamp or phone charger. No power? Press the TEST/RESET button on the GFCI outlet, then check the breaker panel.
- Manually lift the float — reach into the pit and raise the float ball or float arm by hand. If the pump kicks on, the float is stuck, not the pump.
- Inspect the float for obstructions — make sure the float can swing freely without hitting the pit wall, the pump body, or any debris. Re-position the pump or trim the float cord if needed.
- Clear the intake screen — unplug the pump, pull it out of the pit, and rinse the intake screen with a garden hose. Check the impeller opening for debris while you're at it.
- Check the discharge line — follow the pipe from the pump to where it exits the house. Look for a frozen end cap, a blocked or buried outlet, or a missing weep hole that's let it freeze solid.
- Listen for a hum with no water movement — plug the pump back in and listen. A hum means power is reaching the motor but the impeller is jammed or the motor windings have failed. That's a pump-replacement job.
When it's urgent
If your basement is actively flooding and the pump won't start, don't wade into standing water near live electrical outlets or a plugged-in pump — shut the circuit off first. Water and electricity are a serious shock risk. If water is rising fast and you can't safely cut power, call 911 or your utility company before anything else.
DIY vs. call a pro
You can likely DIY
- Resetting a tripped GFCI outlet or circuit breaker
- Manually testing and freeing a stuck float switch
- Cleaning or rinsing the intake screen and impeller housing
- Repositioning the pump so the float moves freely
- Thawing or clearing a frozen discharge line end cap
- Pouring water into the pit to do a full manual test after any fix
Call a pro for
- Replacing a burned-out pump motor or the whole pump unit
- Installing a backup sump pump (battery or water-powered) alongside the primary
- Running a new dedicated circuit or GFCI outlet for the pump
- Diagnosing persistent flooding that the pump can't keep up with — may point to a drainage or grading issue
- Any work in an actively flooded basement where electrical safety is a concern
Estimated cost range
How HouseCue helps
HouseCue is a private, homeowner-first app that turns this from a one-time worry into a tracked plan. Snap a photo for an AI diagnosis, upload your inspection report to auto-build a handbook, and get seasonal reminders for your roof, HVAC, water heater, plumbing, and electrical — so nothing slips. Connecting with a pro is always optional and only when you choose.
See a free diagnosis — no signupFrequently asked questions
My sump pump hums but doesn't pump water — what does that mean?
A hum with no water movement almost always means the impeller is jammed with debris or the motor windings have seized. Unplug the pump, pull it from the pit, and check the impeller opening for gravel or sediment. If the impeller spins freely but the pump still won't move water when plugged back in, the motor is likely burned out and the pump needs to be replaced.
How do I test my sump pump to see if it's working?
The simplest test: slowly pour a five-gallon bucket of water into the pit and watch whether the float rises and the pump kicks on. If it turns on and clears the water, you're in good shape. Run this test every spring before heavy rain season — and after any period of extended dry weather, since a motor that's been idle can seize.
How long should a sump pump last?
Most submersible sump pumps last 7–10 years with normal use. Pumps in high-water-table areas that run frequently tend to wear out faster — sometimes in 5 years. If yours is older than 8–9 years and starts giving you trouble, replacing it proactively is usually smarter than repairing it.
Why did my sump pump stop working during a storm?
Three things commonly knock out a pump mid-storm: a tripped GFCI from moisture or a power surge, an overwhelmed pump that overheated and tripped its internal thermal switch, or a power outage to the house. A battery backup pump is the most reliable fix for outage and overload scenarios — it kicks in automatically when the primary fails.
Should I replace my sump pump even if I got it working again?
Depends on age and what failed. A stuck float you simply freed is a minor fix — clean it up and monitor it. A motor that hummed and seized, or a pump that's 8+ years old and starting to act up, is worth replacing before the next heavy rain. A pump that fails during a storm can mean thousands of dollars in water damage.
Related guides
HouseCue guides are general educational information, not professional inspection, engineering, or contracting advice. Costs vary by market. For safety issues — gas, electrical, structural, or major water — contact a qualified professional.