Sump Pump Not Working? How to Test It and Get Ready for Heavy Rain
By Mike Holt, NJ Master Plumber · July 18, 2024 · 4 min read · Updated November 1, 2026
Quick answer
Only test a sump pump from a dry, safe location, and never touch a submerged plug, outlet or pump in standing water. If it's dry, pour a bucket of water into the pit. The float should rise, the pump should start within seconds, empty the pit and shut off. If power or discharge is questionable, call a qualified professional.
- Difficulty
- Simple test from a dry spot only
- Time
- 10 minutes
- You need
- 5-gallon bucket of water, flashlight
Rather not risk it? A licensed plumber can handle this for you, with written upfront flat-rate pricing options before any work starts.
Water rising in the basement now? Do not touch a submerged plug, outlet or pump, and stay out of the water. Call us. 908-873-6686
In a Central Jersey storm, the sump pump is often the only thing between groundwater and your basement floor. Pumps can fail quietly, so the first sign may be a wet basement. A short test can tell you now. Only perform simple testing from a dry, safe location; do not touch a submerged plug, outlet or pump in standing water. If power or discharge is questionable, call a qualified professional.
How to test a sump pump in 5 steps
Step 1: Check for a dry, safe spot and look at the power
Stand on a dry floor. If there's water around the pit or the pump is submerged, stop here. Don't touch the plug, outlet or pump, and call us. If it's dry, look to see that the pump is plugged in. If the power is questionable or the GFCI has tripped, call a qualified professional.
Step 2: Look in the pit
Lift the cover if it comes off without tools and shine a flashlight in. Look for mud, gravel and debris, and whether the float, the ball or switch that rises with the water, looks caught on the pump, the cord or the pit wall. Don't reach in. Tell us what you see.
Step 3: Pour in a bucket of water
Slowly pour a 5-gallon bucket of water into the pit until the float rises.
Step 4: Watch it start and stop
The pump should switch on within a few seconds, lower the water quickly, then shut off. Listen for grinding or rattling. A pump that hums but doesn't move water, or keeps running after the pit is empty, needs a qualified professional.
Step 5: Check the discharge outside
Go outside and find where the discharge pipe ends. Water should flow out freely and well away from the foundation. If the end of the pipe looks frozen, buried or questionable, call a qualified professional.
Why isn't my sump pump working?
- No power: unplugged, tripped GFCI outlet or breaker
- Stuck float switch: caught on the pump, the cord or debris
- Clogged intake: mud and gravel blocking the screen at the bottom of the pump
- Blocked or frozen discharge line: the water has nowhere to go
- Bad check valve: water runs back into the pit, so the pump cycles over and over
- Burned out or too small: an old pump, or one that can't keep up with heavy rain
Any of these can look the same from the floor, so call a qualified professional if the simple test fails. See our sump pump page and what sump pump replacement costs.
Get ready before heavy rain
Step 1: Test the pump
Run the bucket test above from a dry, safe location a day or two before a big storm, so there's time to get it fixed.
Step 2: Clear gutters and extend downspouts
Clean the gutters and add extensions so downspouts empty several feet from the house. Water dumped next to the foundation ends up in your sump pit.
Step 3: Add a battery backup
Big storms often knock out power right when the pump is needed most. A battery backup pump keeps running for a while during an outage. Check its battery when you test the main pump.
Step 4: Know the sewer backup risk
In heavy rain, town sewers can fill and push sewage back up into the lowest drain in the house. If your basement floor drain has backed up during storms before, ask us about a backwater valve on the main sewer line. See sewer and water lines.
Step 5: Move valuables up
Keep boxes, electronics and anything you'd hate to lose off the basement floor, especially near the sump pit and floor drains. Do this before any water arrives.
Pump failing or basement taking on water? Call 908-873-6686. Outside regular hours, emergency service requires a $250 upfront emergency fee. When paid, the standard $49 service fee is waived. During regular hours there is no emergency fee. Additional repairs are quoted before work begins. We respond immediately upon contact; dispatch and arrival depend on availability and location. Our emergency plumbing page explains what to expect.
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Stop and call us if
- The pump hums but the water level doesn't drop.
- It runs nonstop, or starts and stops every few seconds.
- The breaker or GFCI outlet has tripped, or power is questionable.
- The discharge line looks blocked, frozen or questionable.
- Water comes up through a floor drain instead of the sump pit. That can be a sewer backup.
- The pump is older and you've never had it replaced.
Call 908-873-6686.
Michael Holt
Owner and operator of Plumbing Doctor, NJ Master Plumber (Lic. #36BI01345600) and U.S. Marine Corps veteran.
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