Why is my sump pump not working?

The most common reasons are no power (an unplugged cord, a tripped GFCI outlet, or a tripped breaker), a float switch stuck against the pit wall or pump body so it can't rise, a clogged intake or impeller jammed with silt, a frozen or blocked discharge line, or a worn-out motor. Work through them in that order — power, then float, then intake, then discharge, then motor — because the cheap, common failures sit at the top of the list.

My sump pump is running but not pumping water. What's wrong?

If the motor hums or runs but no water moves up the pipe, the most likely causes are a jammed or broken impeller, an airlock in the pump, a clogged intake screen, or a discharge line that is frozen or blocked. A stuck-closed check valve can also trap water in the line. Unplug the pump, clear the intake, drill a small weep hole if airlocking is the issue, and confirm the discharge is open all the way to its outdoor exit.

Why won't my sump pump turn off?

A pump that never shuts off usually has a float stuck in the up position, a failed check valve letting pumped water fall back into the pit and re-trigger it, a high water table sending more water than the pump can clear, or a pump that is simply undersized for the inflow. Unplug it before it burns out, free or replace the float, and check the check valve and discharge before assuming the pump is too small.

How do I reset a sump pump?

There is no universal reset button on a basic pump. To 'reset' one that has stopped, unplug it for a minute, check that the GFCI outlet and breaker aren't tripped, free the float so it moves through its full range, then plug it back in and pour water into the pit to trigger a full on-off cycle. Pumps with an electronic controller or backup system may have a reset on the control box — check that before assuming the motor is dead.

Is it safe to work on a sump pump with water in the pit?

Only after you cut the power. A sump pit holds water and the pump is plugged into household current, so reaching in with the cord live is a real electrocution risk. Unplug the pump and float switch at the outlet — do not rely on the float being down — and if the outlet, cord, or standing water is anywhere near electrical connections, shut off the circuit at the breaker first or call a professional.

Sump Pump Not Working: Troubleshooting Guide

A sump pump fails at the worst possible time, and almost never with any warning. You go downstairs during a storm and the pit is full, water is creeping across the slab, and the pump just sits there — silent, or humming and doing nothing. The good news is that a sump pump not working is far more often a five-dollar problem than a dead motor. A jiggled float, a tripped outlet, a wad of silt in the intake. Most of the time the pump is fine; something simple is stopping it.

This guide walks the failures in the order a restoration tech actually checks them — cheapest and most common first — so you find the cause fast instead of buying a new pump you didn’t need.

Quick diagnosis: start with power and the float

Before you take anything apart, rule out the two failures that account for most dead pumps. Both take under a minute.

Confirm the pump has power. Follow the cord to the outlet. Is it plugged in fully? Many setups use a stacked “piggyback” plug where the float switch plugs into the back of the pump’s plug — make sure both halves are seated.
Check the GFCI and the breaker. Sump pumps must run on a GFCI-protected outlet, and GFCIs trip on their own from moisture or a power blip. Press the reset button on the outlet. If nothing happens, check the breaker panel for a tripped breaker and reset it.
Look at the float. Lift the pit lid and watch the float. If it’s wedged against the pit wall, the discharge pipe, or the pump body, it can’t rise to trigger the motor. Free it and move it through its full travel by hand.
Re-test. Pour a bucket of water into the pit until the float rises. The pump should kick on within a second or two.

If that brings the pump back to life, you’re done. If it doesn’t, the table below tells you which section to jump to based on what the pump is actually doing.

Match the symptom to the likely cause and the section that fixes it
What the pump does	Most likely cause	Where to look
Totally silent, no hum	No power, tripped GFCI/breaker, dead switch	Power & the switch
Hums but doesn't pump	Jammed impeller, airlock, clogged intake	Runs but moves no water
Runs but no water outside	Frozen or blocked discharge line	The discharge line
Won't shut off / short-cycles	Stuck float or failed check valve	Won't turn off
Noisy, weak, then quits	Worn impeller or dying motor	When the motor is done

The parts to check when a sump pump isn't working: the float that triggers it, the pump and impeller, the check valve, and the discharge line out of the house.

When the pump is totally silent: power and the switch

A pump that makes no sound at all — no hum, no click — is almost always a power or switch problem, not a blown motor.

Rule out power first

Test the outlet itself by plugging in something simple, like a lamp or a phone charger. Dead outlet means the problem is upstream: the GFCI, the breaker, or the circuit, none of which are the pump’s fault. A live outlet with a dead pump points at the pump’s cord or switch.

Test the float switch directly

On most pumps with a piggyback plug, you can test the motor independently of the switch. Unplug the whole assembly, then plug the pump’s plug straight into the outlet, bypassing the float plug. If the motor runs that way, the motor is fine and your float switch is the failure — it’s stuck, miswired, or burned out. Plug everything back the normal way afterward; running a pump dry for more than a few seconds damages it.

A stuck float is the single most common reason a sump pump stops working. The fix is often just clearing silt out of the pit so the float can move, or repositioning the pump so the float isn’t pinned. If the float moves freely and the pump still won’t trigger through it, the switch needs replacing — an inexpensive part. The sump pump maintenance routine exists largely to keep this exact failure from surprising you mid-storm.

The pump runs but no water comes out

This is the unsettling one: you can hear the motor working, but the water level in the pit isn’t dropping. The motor is fine — something between the impeller and the outdoor outlet is blocking flow.

Clogged intake or jammed impeller. Silt, gravel, and debris settle in the pit and get drawn into the intake screen, or a rag or chunk of root jams the impeller so it spins but moves nothing. Unplug the pump, lift it out, and clear the intake screen and the impeller area by hand.
Airlock. Sometimes air gets trapped in the pump housing and the impeller just spins against the bubble. Many pumps have a small weep hole drilled in the discharge pipe below the check valve to release trapped air; if yours doesn’t, a 3/16-inch hole drilled at a 45-degree angle a few inches above the pump (and below the check valve) cures chronic airlocking.
The pump is sitting in muck. A pump resting directly in silt at the bottom of the pit pulls debris straight into the intake. Set it on a flat, hard base — a brick or a pump stand — so it draws cleaner water.

If you’ve cleared the intake and the pump still moves no water, the impeller may be cracked or broken, or the motor may be spinning without engaging the impeller. At that point you’re into replacement territory.

The discharge line: frozen, clogged, or kinked

The pump can be perfect and you’ll still flood if the water has nowhere to go. When the motor runs and the pit slowly empties but nothing comes out the outdoor end, the discharge line is the suspect.

Frozen line. In cold climates this is the classic winter failure: the discharge pipe freezes solid, the pump runs against a closed pipe, overheats, and burns out. Walk to the outdoor outlet and check for ice. Many homes use a freeze-relief fitting near the outlet so water can escape if the buried line ices over.
Clog at the outlet. Leaves, mud, a critter’s nest, or a collapsed pipe blocks the exit. Confirm the outdoor end is open and pointed away from the house.
Kinked or disconnected pipe. A flexible discharge hose can kink, and a glued joint can separate. Trace the line from the pump to the exit and look for the break.

Run the pump and watch the outdoor outlet to confirm strong flow. A weak trickle when the motor is clearly working points to a partial clog or a discharge that’s simply too long or too high for the pump to push against.

The pump won’t turn off

The opposite failure is just as damaging: a pump that runs constantly and never rests will burn out fast. There are four usual causes.

Stuck float (up position). The same float that fails to rise can also fail to fall, jammed at its top of travel so it keeps telling the pump to run. Free it.
Failed check valve. The check valve is a one-way flap that stops pumped water from draining back into the pit. When it fails, that column of water falls back, refills the pit, and re-triggers the pump — over and over. You’ll hear it short-cycle: on, off, on, off, every few seconds. Replacing the valve is cheap and straightforward.
High water table. During a heavy storm or snowmelt, groundwater can genuinely arrive faster than the pump expects. Constant running during an active storm may just be the pump earning its keep — watch whether it catches up once the rain stops.
Undersized pump. If the pump runs nonstop in ordinary conditions and the float and valve are fine, the pump may be too small for your inflow. That’s a sizing problem, not a repair.

A pump that never rests is wearing out in fast-forward, so don’t let “at least it’s still running” lull you. Unplug it, find the cause, and fix it before the motor quits for good.

When the motor is genuinely done

Some failures really are the motor. If you’ve ruled out power, the float, the intake, and the discharge, and the pump is grinding, rattling, buzzing without pumping, or simply dead after years of service, the pump itself has reached the end. Sump pumps last roughly 7 to 15 years, and one that’s worked hard through wet seasons sits at the low end of that range.

Swapping a like-for-like pump in an existing pit is within reach for a confident DIYer: kill the power, disconnect the discharge at the union, lift the old pump out, set the new one on a flat base, re-plumb with a fresh check valve, restore power, and test a full on-off cycle by pouring water in. New pit work, a new discharge route, or new wiring is genuine pro territory.

Why a backup matters more than a fix

Here’s the trap worth naming: the storm big enough to flood your basement is often the same storm that knocks out your power. You can troubleshoot a perfectly healthy pump all day, but a pump with no electricity is a paperweight — and that’s the exact moment you need it most. FEMA’s power-outage guidance treats backup power as a when-not-if item, and a sump system is no different.

A battery backup sump pump mounts higher in the same pit and takes over automatically when the primary loses power or fails. It’s the most valuable upgrade most sump systems can get — more than a fancier primary pump — because it covers the one failure mode you can’t troubleshoot your way out of in the dark.

If the basement is already flooding

Troubleshooting is for a pit that’s filling, not a basement that’s already underwater. If water is across the floor and rising, switch from repair mode to safety mode: cut the power to the area at the breaker before you wade in, treat any standing water near outlets as live, and start water removal. The CDC’s reentry safety guidance and the EPA’s reminder that mold can begin growing within 24 to 48 hours both point the same direction — get the water out and the area dried fast.

Our flooded-basement first steps guide walks the emergency sequence: safety, water removal, drying, and what insurance does and doesn’t cover. Come back to fixing the pump once the immediate water is handled.

The order that actually saves time

When a sump pump isn’t working, resist the urge to assume the worst. Check power and the GFCI, then the float, then the intake, then the discharge, and only then suspect the motor. Four out of five times the fix is free or close to it. Keep the float clean and moving, the discharge clear, and a backup in the pit, and the pump will do the one job it exists for: turn on the night it matters. For the full system view, start with the main sump pump guide.