How often should you test a sump pump?

Short answer

Test the sump pump every 3 to 6 months, and before the rainy season. The test is a bucket of water poured into the pit to lift the float and start the pump, and it takes 10 to 15 minutes and costs nothing. If the pump has a battery backup, test that too, and plan on replacing its battery every 3 to 5 years, because a backup with a dead battery is the same as no backup.

Why it matters

A sump pump sits in a pit at the low point of a basement and pumps out the groundwater that collects there, so the floor stays dry. It only runs when water rises, which in a dry stretch may be months. Then a storm arrives, the pit fills faster than it has in a year, and the pump either starts or it doesn't. A pump that's been idle can seize, its float can stick against the side of the pit, or its check valve can jam, and the first you hear of it is water across the basement floor.

Basement flooding is the kind of damage that ruins everything on the floor and brings mold behind it. The pump that prevents it costs $400 to $1,200 to replace, which is cheap next to the carpet, drywall and furnace it protects, and it lasts 7 to 10 years. A bucket test every few months is how you find out it's still working while the sky is clear.

When to do it more often

Before the rainy season, whenever that falls where you live, and before the spring thaw in a cold climate.
A battery backup pump: test it as well, by unplugging the main pump before the bucket test so the backup has to take over. Replace its battery every 3 to 5 years whether or not it's shown a problem.
A pump that's older than its 7 to 10 year life, or that's been running a lot: lean toward the 3 month end, and keep a spare pump on the shelf.

What you need

A bucket of water, enough to lift the float
A flashlight, to see the pit, the float and the check valve

Steps at a glance

Shine the flashlight into the pit and lift the lid if there is one. Pull out any debris that could jam the float or the pump's intake.
Pour the bucket of water into the pit slowly and watch the float rise.
The pump should start as the float lifts, empty the pit, and shut off on its own.
Listen for the check valve clicking shut after the pump stops, and watch that water doesn't run back into the pit.
For a battery backup, unplug the main pump and pour again. The backup should start and empty the pit.
Plug the main pump back in, and check the discharge pipe outside is clear and pointed away from the house.

You're done when the pump starts on its own, empties the pit, stops, and the pit stays empty afterward.

Signs it's overdue

The pump doesn't start when the float lifts.
The pump runs without stopping, which means the float is stuck or the pump can't keep up.
Grinding or rattling while it runs.
Debris in the pit around the pump.
The check valve rattles, or water runs back into the pit after the pump stops.

DIY or pro

The test is an easy job, and the bucket does the work. Clearing debris from the pit and freeing a stuck float are within reach too, once the pump is unplugged. What you can't do yourself is fix a pump that's seized or burned out, and a pump that fails the bucket test is a pump to replace, not repair.

A plumber charges $400 to $1,200 to replace a sump pump, including the pump. The range depends on the pump's size and whether the check valve and the discharge line need replacing with it. If the pump is near the end of its 7 to 10 years and the bucket test shows anything odd, replacing it on a dry day costs the same as replacing it in a storm and saves the basement.

Safety

Electricity: the pump is an electric motor sitting in water. Unplug it before you reach into the pit to clear debris or free the float, and plug it into a grounded outlet with a working ground fault interrupter. Don't run the pump dry for more than a few seconds, since the water is what cools it.

FAQ

How do you test a sump pump?

Pour a bucket of water into the pit. The float should rise, the pump should start and empty the pit, and it should shut off on its own.

How long does a sump pump last?

Around 7 to 10 years. A pump that runs often wears out at the short end, and one that sits idle for long stretches can seize before then.

Do I need a battery backup sump pump?

If the basement floods when the power is out, yes, because storms that fill the pit also knock out the power. Test the backup with the main pump unplugged, and replace its battery every 3 to 5 years.

Why does my sump pump run constantly?

The float is stuck up, the check valve is letting water run back into the pit, or the pump can't keep up with the groundwater. Unplug it, check the float and valve, and call a plumber if those are fine.