Run the pump on its own to check for power and basic function

The simplest test is to unplug the pump from the outlet, then plug it back in while listening and watching. You should hear the motor start when ready — a humming or whirring sound that lasts a few seconds. If nothing happens, the outlet may be dead, the cord may be damaged, or the pump itself may have failed. Try plugging a lamp or phone charger into the same outlet to rule out a bad outlet first.

Once you hear the motor run, unplug it right away. You are not trying to run it dry for long — most submersible pumps are designed to sit in water and can overheat if they run without it. A few seconds is enough to confirm the motor turns on.

Key Takeaways

  • A working sump pump motor will hum or whir for a few seconds when you plug it in; if it makes no sound, check the outlet and power cord before assuming the pump failed.
  • Never run a submersible pump dry for more than a few seconds, because the water normally cools the motor and running it without water can cause damage.
  • The float switch can be tested by tilting the pump gently to trigger it, which should cause the motor to start without needing to add water to the basin.
  • A dry test tells you whether the pump has power and whether the float switch moves freely, but it cannot tell you whether the pump actually pushes water or whether the discharge line is clear.
  • To fully test pump output, you will eventually need to pour water into the basin or wait for natural groundwater to collect there.

Test the float switch by tilting the pump housing

The float switch is the mechanism that tells the pump when to turn on. It is usually a ball or arm attached to the pump that rises and falls with the water level. To test it without adding water, tilt the pump gently to one side. The float should move freely and trigger the motor to start.

If you tilt the pump and nothing happens, the float may be stuck, the switch may be broken, or the float may be disconnected inside. A stuck float is sometimes fixable — debris or mineral buildup can jam it — but a broken switch usually means the pump needs replacement. Unplug the pump when ready after the motor starts; again, you are only checking that the switch works, not running the pump dry.

Check the discharge line for blockages by blowing through it

The discharge line is the pipe that carries water away from the basin. A clogged line will prevent the pump from working even if the pump itself is fine. To test it without water, disconnect the discharge line from the pump (or from the check valve if one is installed) and blow through it gently. You should feel air move through with little resistance.

If you feel strong resistance or hear a whistling sound, something is blocking the line — ice, sediment, or a collapsed section of pipe. Do not force air through hard; you could damage the line. Instead, note where the blockage is and plan to clear it before the pump needs to run. If the line is above ground and exposed to freezing temperatures, ice buildup is common in winter and will clear on its own as it thaws.

Inspect the power cord and outlet for visible damage

Before plugging in the pump, look at the entire length of the power cord for cuts, cracks, or exposed wires. If you see damage, do not plug it in — a damaged cord is a shock and fire hazard. The cord should also not be pinched under the pump housing or kinked sharply, both of which can damage the insulation over time.

Check the outlet itself for scorch marks, loose connections, or a tripped breaker. If the outlet is a GFCI (ground fault circuit interrupter) — the kind with a test and reset button — press the reset button and try plugging the pump in again. GFCI outlets trip when they sense a ground fault and will prevent the pump from running until they are reset.

Listen for unusual sounds that signal internal problems

When the motor starts, it should make a steady hum or whir. Grinding, squealing, or rattling sounds mean something inside is wrong. A grinding noise usually points to a damaged impeller or bearing. A high-pitched squeal often means the motor bearings are dry or worn. Rattling can be loose internal parts or something stuck in the pump housing.

None of these sounds go away on their own, and running the pump with these problems will make them worse. If you hear any of them, unplug the pump and do not use it until it has been inspected or replaced. A few seconds of listening is enough — you do not need to run it longer to diagnose the problem.

Check that the check valve opens and closes freely

Many sump pumps have a check valve installed on the discharge line. This valve lets water flow out but prevents it from flowing back into the basin when the pump stops. To test it without water, locate the check valve (it is usually a small cylinder on the discharge line near the pump) and gently tap it with your hand. You should hear or feel a light click as the internal flapper moves.

If the valve feels stuck or makes no sound, it may be clogged with sediment or mineral deposits. A stuck check valve will cause the pump to work harder and may prevent it from draining properly. If tapping does not free it, the valve may need to be replaced or flushed out with clean water.

Plan a full test with water once you have ruled out obvious problems

A dry test tells you whether the pump has power, whether the float switch moves, and whether the motor sounds healthy. It does not tell you whether the pump actually moves water or how fast it pumps. For a complete test, you will need to add water to the basin — either by pouring it in with a bucket or by waiting for groundwater to collect naturally.

Once water is in the basin, watch the float rise and the pump start on its own. Listen to the motor and feel the discharge line — it should be warm and you should feel water moving through it. The water level should drop steadily as the pump runs. If the pump starts but the water level does not drop, the pump is running but not moving water, which usually means a clogged impeller or discharge line.

Frequently Asked Questions

How long can I run a sump pump without water?

A few seconds is safe — just long enough to confirm the motor starts. Most submersible pumps rely on water to cool the motor, so running one dry for more than 10 to 15 seconds risks overheating and damage. If you need to test the pump longer, add water to the basin first.

What does it mean if the pump hums but does not start?

A humming sound without the motor turning usually means the pump is stuck or the impeller is jammed. This can happen if sediment or debris has collected inside. Unplug the pump when ready — forcing it to run can burn out the motor. The pump may need to be disassembled and cleaned, or it may need replacement.

Can I test the pump if the basin is empty?

Yes, you can test the motor and float switch with an empty basin. Tilt the pump to trigger the float, and the motor should start. However, you cannot test whether the pump actually moves water without water in the basin, so a dry test is only a partial check.

What should the discharge line feel like when the pump is running?

The discharge line should feel warm or hot to the touch and should have a steady flow of water moving through it. If the line is cool and you feel no water movement, the pump is running but not pushing water — a sign of a clogged impeller or blocked discharge line.

Do I need to test my sump pump regularly?

Yes. A dry test once or twice a year takes a minute and can catch problems before heavy rain or snowmelt forces the pump to work. A full test with water should happen at least once a year, ideally in spring before the wet season begins.