Troubleshooting

Sump Pump Won't Turn On? Here's What to Check

Updated Jul 2026 · 7 min read

When the pit fills but the pump stays silent

A sump pump that won't start is one of the more nerve-wracking things a homeowner can find, usually at the worst possible time: water is rising in the pit, rain is still coming down, and the motor just sits there. Before you assume the worst, know that a dead-quiet pump often comes down to something simple. Here's how to work through it calmly, what you can safely check yourself, and when it's time to stop and call a professional.

A quick word of caution first. A sump pump sits in water and runs on electricity, so treat every step with respect. If you ever feel unsure about the electrical side, or if there is standing water where you'd have to reach, stop and get a licensed pro involved. No troubleshooting step is worth a shock.

Start with power

Most "broken" sump pumps are not broken at all. They have simply lost power. This is the first thing to rule out because it is the most common and the easiest to fix.

Check the outlet the pump is plugged into. Many sump pumps run off a GFCI outlet, the kind with the little reset button, and those can trip without anyone noticing. Press the reset button and see if the pump comes to life. If the outlet is on a wall away from the pit, follow the cord back to be sure it is still fully seated in the receptacle. Vibration over time can work a plug loose.

Next, look at your electrical panel. A tripped breaker will cut power to the pump the same way a tripped GFCI does. Reset it if you find one flipped. If the breaker trips again right away, stop there. A breaker that keeps tripping is telling you something is wrong with the pump or the circuit, and that is a job for an electrician or a plumber, not a repeated reset.

Look at the plug and the piggyback cord

Many submersible sump pumps use what's called a piggyback plug. The float switch has its own plug, and the pump's power cord plugs into the back of it. This design lets you bypass the switch for testing.

Make sure both plugs are fully connected. If everything looks seated and you still have power at the outlet, you can test the pump directly by unplugging the piggyback and plugging the pump's cord straight into the outlet for a moment. If the pump runs when connected directly but stays quiet when the switch is in the circuit, you've found your culprit: the float switch, not the motor.

The float switch: the usual suspect

The float is the part that tells the pump when to run. As water rises, the float rises with it and trips the switch. When that mechanism gets stuck, the pump never gets the signal to start even though the pit is full.

Look down into the pit. A float can jam against the side wall, snag on the discharge pipe, or get pinned by the power cord. It can also get fouled by gunk and sediment that build up over time. Gently free the float and clear away any debris around it. Then lift the float by hand. If the pump kicks on when you raise the float and shuts off when you lower it, the switch is working and the problem was mechanical interference.

Tethered floats need room to swing. If your pump was bumped during a recent cleaning or a stored box slid into the pit, the float may simply not have space to move. Repositioning the pump so the float has clearance often solves it.

A float switch that fails to respond even when lifted has likely worn out. Switches don't last forever, and a replacement is a routine repair for a plumber. If your pump is older and the switch has already failed once, it may be worth weighing a full replacement instead of another patch.

Check for a stuck or clogged impeller

If the pump hums or buzzes but doesn't actually move water, the motor is getting power but the impeller can't spin. The impeller is the small fan-like part that pushes water up and out. Sediment, small stones, or debris that fall into the pit can jam it.

This is where you should unplug the pump before doing anything else. With power off, a clogged impeller can sometimes be cleared by removing the screen or intake cover at the base and clearing out what's blocking it. If you are not comfortable opening the pump, this is a reasonable point to bring in a pro, especially since a motor that keeps trying to drive a jammed impeller can overheat and fail.

Speaking of overheating: many pumps have a thermal cutoff that shuts the motor down when it gets too hot, then resets once it cools. If your pump ran hard during a storm and then went quiet, it may have tripped its own thermal protection. Give it time to cool and see if it restarts. A pump that overheats regularly is working too hard for the water it's facing, which points to a sizing or capacity conversation worth having with an installer.

Don't overlook the discharge side

Sometimes the pump does run, but nothing comes out, and it looks dead from where you're standing. A blockage in the discharge line, a discharge pipe frozen shut in winter, or a check valve installed backward can all stop water from leaving even when the motor is spinning.

Step outside and find where the discharge line exits your home. If it's blocked, buried under debris, or frozen, the water has nowhere to go. In cold climates a frozen discharge line is a common winter failure, and it's one reason discharge routing matters so much at installation.

When to stop and call a professional

DIY checks have a natural stopping point. Call a licensed plumber or sump pump specialist when:

A professional can test the motor, confirm whether the switch or the pump itself has failed, and tell you honestly whether a repair makes sense or whether replacement is the smarter call. If your basement is actively taking on water and the pump won't run, don't wait on this. Move valuables off the floor, manage the water however you safely can, and get a pro out quickly.

A little prevention goes a long way

Most no-start failures trace back to a stuck float, lost power, or a clogged intake, and all three are easier to catch before a storm than during one. Test your pump by pouring water into the pit and watching it cycle on and off. Keep the pit free of sediment and debris. And if your home relies on the pump to stay dry, consider talking to an installer about a backup system so a single point of failure doesn't leave your basement unprotected.

Browse the directory to find qualified sump pump installers near you who can inspect, repair, or replace a pump that won't turn on.