Test your sump pump by pouring water into the pit until the float rises and the pump turns on
The simplest way to know whether your sump pump will work when you need it is to make it work now, while the basement is dry. Fill a bucket with water and pour it slowly into the sump pit until the water level rises enough to trigger the float switch. You should hear the pump motor start and see water being pushed out through the discharge pipe. If nothing happens, or if the pump runs but water stays in the pit, you have a problem to fix before the next storm.
This test takes five minutes and tells you whether the pump itself, the float mechanism, and the discharge line are all functioning. It does not require tools or special knowledge, and it costs nothing. Most homeowners should run this test twice a year — once in spring and once in fall — because sump pumps fail silently, and you will not know yours is broken until water starts backing up into your basement.
Key Takeaways
- Pour water into the sump pit slowly until the float rises and triggers the pump; the motor should start and water should exit through the discharge pipe.
- If the pump runs but water does not drain, the discharge line is blocked or the check valve is stuck — both require clearing before heavy rain.
- If the pump does not run at all, check that the outlet is plugged in, the circuit breaker has not tripped, and the float is not stuck against the pit wall.
- Test your pump twice yearly and after any power outage, because a failed pump will not alert you until water is already in your basement.
- If the pump runs but makes grinding noises or the water level does not drop, call a plumber — the pump may be failing internally.
What happens during a normal sump pump test
When you pour water into the pit, the rising water level lifts a float ball or switch that is attached to the pump's electrical circuit. Once the float reaches a certain height — usually around 12 inches of water in the pit — it closes an electrical contact and sends power to the pump motor. You will hear the motor start with a hum or a click, and within a few seconds you should see water flowing out of the discharge pipe that runs from the pump to the outside of your house or to a storm drain.
The water should drain quickly enough that the pit empties within a minute or two. As the water level drops, the float sinks back down and breaks the electrical contact, shutting the pump off. This cycle — water rises, pump turns on, water drains, pump turns off — is what keeps your basement dry during rain or snowmelt. If any part of this cycle fails, water will accumulate in the pit and eventually seep into your basement.
What to check if the pump does not turn on
Start with the simplest things first. Look at the outlet where the pump is plugged in and make sure the cord is fully inserted and the outlet itself has power — plug in a lamp or phone charger to confirm. Check your electrical panel for a tripped circuit breaker; if the breaker switch is in the middle position or flipped toward "off," switch it back to "on" and try the test again.
Next, look inside the sump pit. The float should move freely up and down. If it is wedged against the pit wall, stuck on the pump housing, or tangled in a cord, it cannot rise to trigger the switch. Gently move the float by hand to make sure it moves smoothly. Also check that nothing is blocking the intake screen on the pump itself — leaves, sediment, or debris can prevent water from entering the pump even if the motor is running.
If the outlet has power, the breaker is on, and the float moves freely, the problem is likely inside the pump or the switch mechanism. This is the point to call a plumber, because the pump may need repair or replacement.
What to do if the pump runs but water does not drain
If you hear the motor running but the water level in the pit stays high or drops very slowly, the problem is almost always a blocked discharge line or a stuck check valve. The discharge pipe carries water from the pump to the outside of your house, and if it is frozen, clogged with sediment, or kinked, the water has nowhere to go.
Follow the discharge pipe from the pump to where it exits your house. Look for kinks, cracks, or obvious blockages. If the pipe runs outside, check that the exit point is not covered with ice, leaves, or debris. Some discharge lines have a one-way check valve near the pump to prevent water from flowing backward into the pit when the pump is off; if this valve is stuck closed or clogged, water cannot leave the pit even though the pump is running.
If you find a kink, straighten it. If the exit is blocked, clear it. If you suspect the check valve is stuck, you may be able to tap it gently with a hammer to free it, but if that does not work, the valve will need to be replaced. A plumber can do this quickly, and it is worth doing before the next rain.
What unusual sounds mean during a test
A normal sump pump makes a low hum when it starts and a steady, quiet whirring sound while it runs. When it shuts off, you may hear a brief click or a small splash as the water stops flowing.
Grinding, squealing, or rattling sounds during the test mean something inside the pump is wearing out or broken. A grinding noise usually means the impeller — the spinning part that moves water — is hitting something or the bearings are failing. A squealing sound often means the motor bearings need lubrication or are about to fail. These sounds mean the pump is still working now, but it will not work much longer. Plan to replace it soon, and consider having a plumber install a backup pump or a battery-powered backup system so you are not without drainage during the next heavy rain.
Testing after a power outage or long shutdown
If your power has been out for more than a few hours, or if your sump pump has sat unused for several months, run a test before you rely on it. Sump pumps can develop problems while sitting idle — the impeller can rust slightly, the check valve can stick, or sediment can settle in the intake. A test will reveal these issues before they cause a flooded basement.
Pour water into the pit as you normally would and watch for the same signs: the pump should start, water should flow out the discharge pipe, and the pit should drain. If the pump is sluggish to start, makes unusual noises, or drains slowly, have it inspected by a plumber before the next rain. If it works normally, you are good until your next scheduled test.
When to call a plumber instead of testing yourself
Do the basic water-pour test yourself — it is safe and takes five minutes. But if the test reveals any of these problems, call a plumber: the pump does not start even though power is on and the float moves freely; the pump runs but makes grinding or squealing noises; water drains very slowly or not at all even after you have cleared the discharge line; or the pump cycles on and off rapidly without draining the pit.
Also call a plumber if your sump pump is more than 10 years old and you have never had it serviced. Pumps wear out, and an old pump that passes a basic test today may fail during the first heavy rain of the season. A plumber can inspect the pump, clean the intake and discharge lines, test the check valve, and tell you whether replacement is coming soon.
Frequently Asked Questions
How often should I test my sump pump?
Test it twice a year — once in spring and once in fall — to catch problems before heavy rain season. Also test it after any power outage lasting more than a few hours, because the pump may have tripped offline and not restarted automatically.
Can I test the pump if it is raining outside?
Yes, but the test will be harder to see because the pump may already be running to handle rainwater. Wait for the rain to stop and the pit to drain, then run your test. If the pit does not drain after the rain stops, that is a sign the pump is not working and you should call a plumber when ready.
What if water comes back up into the pit after the pump stops?
That means the check valve is not sealing properly. The check valve is supposed to let water out but not back in. If water flows backward into the pit when the pump is off, the valve is stuck or damaged and needs to be replaced by a plumber.
Do I need to add anything to the sump pit before testing?
No. Use plain tap water from a bucket or hose. Do not add chemicals or cleaning products. The pump is designed to move water only, and anything else can damage the motor or clog the discharge line.
Is it normal for the pump to run for just a few seconds?
Yes, if you only pour a small amount of water in. The pump will run until the water level drops below the float trigger point, which may be only 10 or 15 seconds if you added just a bucket or two. For a more thorough test, pour water until the pit is half full, so the pump runs for 30 seconds to a minute.