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Knowing how to test a sump pump takes about 15 minutes and a bucket of water, and it’s the difference between a dry basement and a flooded one. Most pumps sit quietly in a corner of the basement for months, so nobody notices when one stops working. Usually you find out during the first big storm.
This guide covers how a sump pump works, how often to test it, the 6 steps to test a sump pump the right way, how to keep the discharge line from freezing this winter, and when it’s time to replace the pump or add a backup.
WHAT’S IN THIS GUIDE
How a Sump Pump Works
A sump pump sits in a pit, called the sump, in the lowest part of the basement. Groundwater drains into the pit through drain tile around the foundation. When the water rises, a float rises with it and switches the pump on. The pump pushes the water up a pipe and out of the house, then shuts off when the float drops back down.
There are two common types:
- Submersible pumps sit at the bottom of the pit, under the water. They’re quieter and the most common type in newer homes.
- Pedestal pumps have the motor on a post above the pit, with the float visible on a rod. They’re easy to watch while you test them.
Either way, North Dakota State University Extension says every pump should have a check valve on the discharge pipe. Without one, the water in the pipe runs back into the pit each time the pump shuts off, so the pump runs more often and wears out faster. Source: NDSU Extension — Sump Pump Questions
How Often to Test a Sump Pump
Test it at least twice a year: once in the fall before the ground freezes, and again in early spring before the heavy rains and snowmelt. If your pump runs a lot, or if you’ve ever had water in the basement, check it every few months. It also pays to test it any time a big storm is in the forecast.
How to Test a Sump Pump in 6 Steps
Here’s how to test a sump pump from start to finish. You’ll need a 5-gallon bucket of water, a flashlight and a pair of work gloves for handling anything in the pit.
Step 1: Check the discharge line outside
Start outside. Find where the pump’s pipe comes out of the house and make sure the end isn’t buried, crushed, clogged with leaves, or frozen shut. NDSU Extension says to check that the outlet pipe isn’t frozen or plugged before you test, because a pump pushing against a blocked pipe can’t move any water. Source: NDSU Extension — Time to Check Your Sump Pump
Step 2: Clean the pit and the intake screen
Unplug the pump. Take the lid off the pit and shine a flashlight inside. Pull out any gravel, mud, or debris sitting around the pump. NDSU notes that these pumps don’t have filters, but they do have screens or small openings where water enters, and those can get plugged. A shop vac makes quick work of the sludge at the bottom. Source: NDSU Extension — Time to Check Your Sump Pump
While you’re in there, make sure the float can move freely and isn’t caught on the pump, the cord, or the side of the pit.
Step 3: Check the power
Plug the pump back in and check the cord for damage. If the pump is plugged into a GFCI outlet, make sure it hasn’t tripped. A tripped outlet shuts the pump off without any warning. That’s one of the best reasons to add an alarm (more on that below). Our guide on how to test a GFCI outlet shows how to find and reset one.
Step 4: Pour water in slowly and watch it cycle
This is the step most people picture when they learn how to test a sump pump. Slowly pour water from the bucket into the pit until the float rises and the pump kicks on. NDSU Extension recommends pouring slowly, about as fast as water normally comes in, and making the pump cycle on and off at least twice. Watch that it turns on, empties the pit, and shuts itself off. Source: NDSU Extension — Time to Check Your Sump Pump
Listen while it runs. A smooth hum is normal. Grinding, rattling, or a pump that hums but doesn’t move water means something’s wrong, and NDSU says to get it fixed as soon as possible.
Step 5: Check the check valve
When the pump shuts off, you should hear a soft thunk as the check valve closes. Then watch the pit for a minute. If water comes rushing back down the pipe into the pit, the check valve is worn out or stuck open. It’s an inexpensive part to replace, and it saves wear on the pump.
Step 6: Test the backup
If you have a battery backup pump, test it too. NDSU Extension says to make sure the battery is fully charged, then cut power to the main pump and pour water in until the backup starts. Source: NDSU Extension — Time to Check Your Sump Pump
Plug the main pump back in when you’re done. Forgetting this step is how a sump pump test turns into a flooded basement.
Keep the Discharge Line From Freezing
In Indiana, the biggest winter sump pump problem isn’t the pump. It’s the pipe outside. Water left in the end of the discharge line can freeze solid, and then the pump has nowhere to send the water. NDSU Extension notes that almost all sump pump motors have built-in thermal protection that shuts them off if they overheat. If that happens, unplug the pump, let it cool, and clear the ice. The thermal switch resets once the motor cools down. Source: NDSU Extension — Sump Pump Questions.
A few things help keep the line clear all winter:
- Make sure the pipe slopes downhill away from the house so water drains out instead of sitting in it.
- Keep the end of the pipe clear of snow and leaves.
- Use a sump pump discharge hose or extension that unrolls flat and drains completely, and roll it up when it’s not needed. Most home sump pumps use a 1 1/2-inch discharge pipe, but measure yours before you buy.
Our guide on how to prevent frozen pipes covers the rest of the plumbing to protect before a hard freeze.
Where Sump Pump Water Should Go
NDSU Extension recommends discharging sump water at least 20 feet from the house, and away from window wells, septic fields, and the neighbor’s yard. Water dumped right next to the foundation just soaks back down to the drain tile, and the pump ends up moving the same water over and over. NDSU also warns never to pump sump water into a basement floor drain, since it can damage a septic system or overload the public sewer. Source: NDSU Extension — Sump Pump Questions
Check your city’s rules, too. Here in Greenwood, a 2016 city ordinance requires sump pump discharge to land outside any drainage or utility easement and no closer than 20 feet from the street right-of-way. Other cities have their own rules, so call your local public works office if you’re not sure. Source: City of Greenwood, Indiana — Ordinance No. 16-48, Sump Pump Discharge Regulations
If water from the pump or your gutters keeps pooling near the house, see our guides on how to extend downspouts away from your house and window well flooding.
Backup Pumps and Alarms
A sump pump fails at the worst possible time: during a storm, when the power goes out. The City of Ann Arbor’s guide to sump pump backups compares the common options:
- Battery backup pumps. The most popular choice. They switch on automatically during a power outage, but the battery generally lasts 7 to 24 hours of pumping and needs replacing about every three years.
- Water-powered backup pumps. These run on your home’s water pressure, using about 2 gallons of city water to pump out 1 gallon. They don’t need power, but they don’t work on a well.
- Generators. A portable generator can run the main pump, but someone has to be home to start it.
- High-water alarms. An alarm sounds when the water in the pit rises above where the pump should have turned on, which gives you time to act.
Source: City of Ann Arbor — Sump Pump Backup Options
For most homes, a battery backup sump pump is the best upgrade. Most, including this one, don’t come with the battery, so plan on buying a deep-cycle battery made for sump pumps separately. At the very least, put a smart water leak sensor on the basement floor next to the pit. It sends an alert to your phone the moment water gets out, even if you’re at work.
When to Replace a Sump Pump
There’s no set schedule for replacing a sump pump, so let your twice-a-year test tell you. If yours is getting old, keep a spare pump of the same size on hand so you can swap it in fast if the old one quits during a storm. NDSU Extension notes that replacing a sump pump isn’t a difficult job for the average homeowner. Source: NDSU Extension — Sump Pump Questions.
Replace it sooner if it runs constantly, cycles on and off every few seconds, makes grinding noises, or has rust or corrosion on the housing. And if you’ve already had water in the basement, walk through our guide on how to check for water damage. Testing the sump pump is also one of the tasks on our winter home maintenance checklist.
Frequently Asked Questions About Sump Pumps
How do I know if my sump pump is working?
Pour a bucket of water slowly into the pit. A working pump turns on when the float rises, empties the pit, and shuts off by itself. If it doesn’t turn on, hums without pumping, or never shuts off, it needs attention.
How often should you test a sump pump?
At least twice a year: in the fall before the ground freezes and in early spring before the heavy rains. Test it more often if it runs a lot or if a big storm is coming.
Why is my sump pump running but not pumping water?
The most common causes are a frozen or clogged discharge line, a plugged intake screen, or a check valve that’s stuck. Unplug the pump, check the line outside, and clean the intake before calling a plumber.
Can a sump pump freeze in winter?
The pump itself is usually below the frost line, but the discharge pipe outside can freeze. If the pump runs and nothing comes out, check the end of the pipe for ice.
How long do sump pumps last?
It depends on how often yours runs. Instead of going by age, test it twice a year and replace it when it fails the test, runs nonstop, or starts grinding. If yours is getting old, keep a spare on hand.
Do I need a battery backup sump pump?
If your basement is finished or your pump runs often, yes. Power outages and storms usually happen at the same time, and a battery backup keeps pumping when the main pump can’t.