Master Plumber's Log · Published 2026-10-13
Is Your Sump Pump Failing? Signs, Safe Checks, and When to Call
The short answer
A sump pump is in trouble when it stays silent while the pit fills, runs without stopping, hums without moving water, or switches on and off every few seconds. Each symptom points somewhere different: power or the float switch, a blocked intake or impeller, a failed check valve, or more water coming in than the pump can handle. You can safely confirm which one you have with a bucket of water and your ears. Deciding whether the fix is a part or a new pump takes someone looking at the equipment.
If water is coming into the basement right now, skip to If the basement is already wet. Safety comes before diagnosis.
Test it before the next storm
The simplest check is the one manufacturers and inspectors both recommend: pour water into the pit and watch. InterNACHI’s inspection guidance says the pump “can be tested by pouring water into the pit to make sure it becomes activated and expels the water” (InterNACHI).
- Lift the pit cover and look before you pour. Note any debris, silt, or gravel around the pump.
- Pour a bucket or two of water in slowly until the float rises.
- The pump should start on its own, lower the water, and shut off.
- Listen after it stops. A short rush of water back into the pit, or a thud from the pipe, is worth mentioning to a plumber.
Zoeller’s installation instructions for its backup-pump system say to inspect and test the system for proper operation at least every three months (Zoeller Pump Company). InterNACHI recommends maintenance annually and when the home is sold (InterNACHI). Late summer, before fall storms, is a sensible time to test. So is the day you buy the house.
Do not reach into the pit while the pump is plugged in, and do not take the pump apart. If the test fails, stop there and write down what you saw.
What each symptom usually means
| What you notice | Common causes | What you can safely check |
|---|---|---|
| Pump stays silent while the pit fills | No power, tripped breaker or GFCI outlet, float stuck in the down position, failed switch or motor | Is it plugged in? Is the outlet live? Is anything touching the float? |
| Pump runs and never shuts off | A lot of water coming in, or the float stuck in the on position (Pentair) | Is the water level actually dropping? Has it been raining hard? |
| Pump hums or runs but water doesn’t drop | Blocked intake, air lock, stuck check valve, damaged impeller (Pentair) | Is the discharge pipe frozen, crushed, or buried outside? |
| Pump switches on and off every few seconds | Missing or failed check valve, discharge restriction, or a float set too tight for the pit | After it stops, does water rush back down the pipe into the pit? |
| Loud banging, rattling, or grinding | A rattling discharge pipe, a slamming check valve, the pump sucking air, or impeller damage (Pentair) | Is the noise from the pipe or from inside the pit? |
The pump is silent
Start with power. Many sump pumps plug into a nearby outlet, and a tripped breaker or outlet is the cheapest problem you will ever find. If the outlet is live and the pump still sits there while water rises, the float may be caught on the pit wall or the pump cord. If you can see that and fix it without reaching into the water, do. If not, the next step is a plumber, not a screwdriver.
The pump runs without stopping
During a long rain this may simply be the pump doing its job. Watch the water level. If it holds steady or drops, the pump is keeping up. If the pit is dry or nearly dry and the pump keeps running, the float is likely stuck in the on position. A pump that runs dry for hours can overheat, so this one should not wait for a convenient week.
The pump hums but nothing happens
The motor is getting power, but water isn’t moving. The usual suspects are a clogged intake screen, a damaged impeller, a check valve that is stuck closed, or air trapped in the pump. Outside, look at where the discharge line ends. A pipe that is crushed, frozen, or buried under mulch can back water up to the pump.
The pump short-cycles
A check valve keeps the water in the discharge pipe from falling back into the pit when the pump stops. Without one, InterNACHI notes, the pump has to work twice as hard to remove the same water (InterNACHI). If you hear water rush back into the pit every time the pump shuts off, that valve is the first thing to ask about. Frequent starts and stops wear out the switch.
Repair or replace: what actually decides it
Age is part of it. Zoeller says its pumps average 7 to 10 years with proper installation and maintenance, and that actual lifespan varies with conditions (Zoeller at Home). That is a manufacturer’s average, not a deadline. A 12-year-old pump that tests fine is not an emergency, and a 3-year-old pump with a failed motor is not worth nursing along.
What decides the call:
- What failed. A stuck float, a failed switch, or a bad check valve is often a part. A burned-out motor usually means a new pump.
- Whether it keeps happening. A pump that needs the same fix twice in a season is telling you something.
- What else is wrong with the setup. A new pump on a crushed discharge line or a pit full of silt will fail the same way.
- What sits in the basement. A finished basement, stored belongings, or a furnace and water heater near the pit raise the cost of a failure. Zoeller recommends a backup system if the area is prone to power outages or the basement is finished or used as living space (Zoeller at Home).
Spangler Plumbing repairs, replaces, and installs sump pumps for homeowners across New Castle County. We look at the pump and how it is set up, then lay out the options. See the full list of plumbing services or contact us to set up a visit.
One local rule about where the water goes
In New Castle County, sump water does not belong in the sewer. The county building code makes it unlawful to connect a sump pump “directly or indirectly into any public or private sewer” without written authorization from the county’s General Manager of Public Works (New Castle County Code, Chapter 6, Sec. R325.9). If your discharge line runs into a laundry tub or floor drain, raise it at the service visit. InterNACHI also recommends discharging water at least 20 feet from the building so it does not cycle back toward the foundation (InterNACHI).
If the basement is already wet
Protect people first, then the pump.
- Stay out of standing water if it may be touching outlets, cords, appliances, or the panel. Safe Electricity puts it plainly: “Never step into a flooded basement or other room if water may be in contact with electrical outlets, appliances or cords” (Safe Electricity).
- Do not shut off power at a breaker box if you would have to stand in water to reach it. Call your electric utility instead (Safe Electricity).
- If anyone is in immediate danger, call 911.
- Once everyone is safe, contact Spangler Plumbing promptly and tell us what the pump is doing. The guide to what counts as a plumbing emergency can help you decide how urgent the rest of the situation is.
Questions homeowners ask
How do I know if my sump pump is working?
Pour water into the pit until the float rises. A working pump starts on its own, lowers the water, and shuts off. InterNACHI recommends this test, and it takes a few minutes.
Why does my sump pump keep turning on and off?
The most common causes are a missing or failed check valve, which lets pumped water fall back into the pit, a restricted discharge line, or a float set too tight for the pit. Frequent cycling wears out the switch, so have it checked.
Why is my sump pump running but not pumping water?
The motor has power but water is not moving. Pentair lists a blocked intake, an air-locked pump, a stuck check valve, and a damaged impeller as the usual causes. A frozen or crushed discharge line outside can do the same.
How long does a sump pump last?
Zoeller puts its average at 7 to 10 years with proper installation and maintenance, and says actual life varies with use. Age alone does not decide replacement. What failed and how often it fails matter more.
Should I repair or replace my sump pump?
It depends on what failed. A float, switch, or check valve is often a repair. A burned-out motor, repeat failures, or an old pump in a finished basement usually points to replacement. A plumber should confirm the cause before you pay for either.
Can a sump pump drain into the sewer in New Castle County?
No, not without written authorization. New Castle County’s building code makes it unlawful to connect a sump pump directly or indirectly to a public or private sewer unless the county’s General Manager of Public Works approves it in writing.
What to do this week
Pour a bucket of water into the pit and watch the pump start, empty, and stop. Walk outside and find the end of the discharge line. If the pump failed the test, short-cycles, or is old enough that you cannot remember when it went in, write down what it does and contact Spangler Plumbing. We repair, replace, and install sump pumps across New Castle County.