Sump pumps have an unusual job. They sit idle for weeks, then are asked to work flat out during the worst weather of the year — often during a power cut. That is why they tend to fail at exactly the moment they are needed, and why testing one before it matters is worth more than any repair after.
Across the Upstate, most sump pumps protect crawlspaces or basements from groundwater and runoff during heavy rain. Red clay drains poorly, and on sloped lots water can arrive at the foundation faster than people expect.
The bucket test
Slowly pour a bucket of water into the sump pit until the float rises. A working pump should start, empty the pit, and shut off cleanly.
| Nothing happens | Power, or a float switch that is not rising. Check those first. |
| Hums but water does not drop | A jammed impeller, a clogged intake, an airlock, or a blocked discharge line. |
| Runs but pumps slowly | Partial blockage, worn impeller, or a pump too small for the lift. |
| Empties, then refills and restarts | Water running back down the discharge pipe. A missing or failed check valve. |
| Will not shut off | Float stuck in the up position, a failed switch, or groundwater flowing in as fast as it pumps out. |
Common causes, and what to do
Power
Sump pumps are usually plugged into a GFCI outlet, and GFCIs trip — sometimes from moisture, sometimes from a fault. Press the reset button. Check the breaker. Make sure the plug has not worked loose.
If the GFCI trips again immediately, there may be a fault in the pump or its cord. Do not bypass it and do not run the pump from an extension cord as a permanent fix.
Float switch
The float tells the pump when to start. Tethered floats can snag on the pit wall, the pump body or the discharge pipe. Vertical floats can stick on debris. Look into the pit and make sure the float moves freely through its full range.
A pump that has shifted in the pit is a common cause: it moves slightly each time it starts, until one day the float is trapped against the wall.
Clogged intake or impeller
Silt, gravel and debris build up in the bottom of the pit and get drawn into the pump. Many pits in our area collect fine red clay that settles into a thick layer. Unplug the pump, lift it out, and clean the intake screen and the pit.
Blocked or frozen discharge line
If the pump runs but water does not leave, the discharge line may be blocked by debris, crushed where it runs underground, or frozen at the outlet in winter. Check where the line exits the house and make sure it discharges well away from the foundation.
Airlock
Air trapped in the pump housing can stop it moving water. Most installations have a small weep hole drilled in the discharge pipe just above the pump to prevent this. If yours does not, that is worth adding.
A worn-out pump
Sump pumps commonly last somewhere around seven to ten years, less if they run often. A pump that is noisy, slow, or tripping the GFCI, and is in that age range, is due for replacement before it fails in a storm.
Unplug it before reaching into the pit. Water and electricity in a confined space is not something to take chances with. And if the pit is already overflowing, deal with the water first — a wet-vac or a temporary pump — then investigate.
The failure nobody plans for: the power cut
The heaviest rain often arrives with the storms that knock out power. A perfectly healthy sump pump does nothing without electricity. That is the case for a battery backup pump, covered in whether a battery backup sump pump is worth it.
A simple maintenance routine
- Every few months and before storm season: the bucket test.
- Once a year: lift the pump, clean the intake, clear the pit, check the check valve and the discharge outlet.
- Before winter: make sure the discharge line drains fully and cannot freeze at the outlet.
- If you have a backup: test the battery and the backup pump separately.
Where we work
Sump pump service across Upstate South Carolina
| ✓Anderson | ✓Greer |
| ✓Taylors | ✓Mauldin |
| ✓Simpsonville | ✓Fountain Inn |
| ✓Travelers Rest | ✓Easley |
What to remember
| 1 | Test before the storm. A bucket of water, a minute of your time. |
| 2 | Check the GFCI first. It is the most common reason for a silent pump. |
| 3 | Free the float. A snagged float stops a healthy pump. |
| 4 | Clean the pit yearly. Clay and silt build up and choke the intake. |
| 5 | Plan for the power cut. The heaviest rain often comes with one. |
Frequently asked questions
Why is my sump pump not turning on?
Most often a tripped GFCI outlet or breaker, a loose plug, or a float switch that is stuck or snagged and not rising with the water. A failed switch or motor is less common.
How do I test my sump pump?
Slowly pour a bucket of water into the pit until the float rises. The pump should start, empty the pit and shut off cleanly.
Why does my sump pump run but not pump water?
A clogged intake, a jammed impeller, an airlock in the housing, or a blocked or frozen discharge line. Unplug the pump before checking any of them.
Why does my sump pump keep turning on and off?
Usually water running back down the discharge pipe into the pit because the check valve is missing or has failed. A float set with too little range can also cause frequent cycling.
Why won’t my sump pump shut off?
The float may be stuck in the raised position, the switch may have failed, or groundwater may be entering the pit as fast as the pump removes it during very heavy rain.
How long do sump pumps last?
Commonly around seven to ten years. Pumps that run frequently, or handle a lot of silt, tend to wear out sooner.
Can I plug my sump pump into an extension cord?
Only as a short-term emergency measure. A sump pump should be plugged directly into a properly grounded GFCI outlet.
Sump pump failed the bucket test?
Get it fixed before the next storm
We repair and replace sump pumps across the Upstate, check the float, check valve and discharge line, and give you a fixed price in writing before any work starts.
Open 7am–9pm, seven days · No call-out fee with a repair · Fixed price agreed in writing
See our sump pump repair page, or read about battery backup sump pumps.
