Pump runs continuously with no visible water
You hear the motor running or humming, but the pit is empty or nearly empty and the float looks high or trapped.
Start here: Start with the float switch and cord routing.
Sump Pump Troubleshooting
Sump Pump Runs With Dry Pit
Direct answer: A sump pump that keeps running with a dry pit is usually being told to run when it should not. Most often that means a float switch is stuck, tangled, or failed. The next most common lookalike is water dropping back into the pit because the sump pump check valve is leaking or installed wrong.
Most likely: Start by watching the float while the pump is unplugged. If the float is jammed high or the switch cord is tangled, that is the first fix. If the float drops normally but water falls back into the pit after each cycle, suspect the sump pump check valve.
Separate the problem by what you actually see: a dry pit with the pump still humming points to a switch issue, while a pit that empties and then refills from the discharge line points to backflow. Reality check: many "bad pump" calls end up being a stuck float. Common wrong move: lifting or tying the float up to keep the basement dry and then forgetting it there.
Don’t start with: Do not start by buying a whole sump pump just because the motor still runs. A bad float switch or check valve is more common and a lot cheaper.
If the pit is truly dry and the pump still runs,check the float switch position and movement first.
If the pit empties and then quickly refills,look for backflow through the sump pump check valve before blaming the pump.
Last reviewed: 2026-04-05
What this usually looks like
Pump stops, then starts again a minute later
The pit empties, then water drops back in from the discharge pipe and the pump cycles again.
Start here: Start with the sump pump check valve and discharge line direction.
Pump hums but does not seem to move water
The motor sounds live, but the water level does not change much or the pit is already dry and the pump keeps straining.
Start here: Shut power off and check for a jammed impeller or a switch stuck closed.
Pump only runs nonstop during heavy rain
The pit is not always dry, but the pump barely gets a break and may keep restarting after each cycle.
Start here: Watch whether water is returning to the pit or whether incoming water is simply overwhelming the system.
Most likely causes
1. Stuck or tangled sump pump float switch
This is the most common reason a sump pump runs with little or no water in the pit. The float can hang on the pit wall, discharge pipe, pump body, or its own cord.
Quick check: Unplug the pump and move the float by hand. It should rise and fall freely without rubbing or snagging.
2. Failed sump pump float switch
If the float moves normally but the pump runs whenever it has power, the switch contacts may be stuck closed.
Quick check: With the pit dry, restore power only long enough to test. If the pump starts even with the float fully down, the switch is likely bad.
3. Leaking or backward sump pump check valve
A bad check valve lets pumped water fall back into the pit, which makes the pump cycle again and can look like it never really shuts off.
Quick check: Run one cycle and listen at the discharge pipe. A strong rush of water dropping back into the pit after shutoff points to backflow.
4. Pump internal switch or control failure
Some sump pumps have an integral switch or internal control that can fail in the run position. This is less common than a float issue but it happens.
Quick check: If the float branch checks out and the pump still runs with the switch down, the pump itself is the likely fault.
Step-by-step fix
Step 1: Make the area safe and confirm the pit is actually dry
You want to separate a true run-on problem from a pump that is still doing real work during a storm. It also keeps you from handling a wet electrical setup carelessly.
- If the pump is plugged into a receptacle, unplug it before reaching into the pit area or touching the float.
- Use a flashlight and look at the water level, not just the sound of the pump.
- Check whether the pit is empty, nearly empty, or quietly refilling from the drain tile.
- Look for obvious splashback or water dropping from the discharge pipe into the pit after the pump stops.
- If there is standing water around the receptacle, extension cord, or plug connection, leave power off and dry the area before testing.
Next move: You now know whether you have a true dry-pit run-on problem or a refill problem caused by returning water. If you cannot safely access the plug, receptacle, or pit area, stop here and call for service.
What to conclude: A truly dry pit points you toward the float switch or pump controls. A pit that refills right after pumping points toward the check valve or discharge line.
Stop if:
- There is standing water at the electrical outlet or plug connection.
- The pump cord, plug, or receptacle looks scorched, loose, or damaged.
- You cannot unplug the pump safely.
Step 2: Watch the float switch move through a full up-and-down cycle
This separates the most common failure fast. A float that cannot drop will keep calling for the pump even when the pit is empty.
- With power still off, locate the sump pump float switch and its cord.
- Move the float up and down by hand. It should move freely and return down without catching on the pit wall, discharge pipe, pump handle, or cords.
- Untangle any cord slack that can loop around the float.
- Clear away debris, gravel, or sludge that is pinning the float in the up position.
- If the float is on a vertical rod, make sure it slides freely and is not crusted up with buildup.
Next move: If the float was stuck and now drops freely, restore power and watch one cycle. The pump should shut off once the water level falls. If the float already moves freely and the pump still runs whenever it has power, keep going to the switch test.
What to conclude: A jammed float is a simple mechanical problem. A free-moving float with a pump that still runs points to a failed switch or internal control.
Step 3: Test whether the switch is stuck closed
A float can look normal but still fail electrically. This is the point where you separate a bad sump pump float switch from a bad pump.
- With the pit dry and the float resting fully down, restore power briefly.
- If the pump stays off with the float down, lift the float by hand to confirm the pump starts, then lower it to confirm it stops.
- If the pump starts immediately even with the float fully down, unplug it again.
- On a tethered or piggyback style setup, make sure the pump plug and float switch plug are connected in the normal order and not bypassed.
- If someone previously plugged the pump directly into the wall to override the switch, reconnect it correctly before judging the switch.
Next move: If the pump only runs when you lift the float and stops when you lower it, the switch is working. Move on to check for backflow if the pump keeps cycling later. If the pump runs with the float down and correctly connected, the sump pump float switch is likely failed closed or the pump has an internal control fault.
Step 4: Check for water falling back into the pit after shutoff
Backflow can make a pump look like it runs all the time when the real problem is that the same water keeps returning.
- Run the pump through a normal cycle and watch the pit as the water level drops.
- Listen at the discharge pipe right after shutoff for a rush or glug of water returning.
- Inspect the sump pump check valve on the discharge line for the flow arrow direction and obvious leakage.
- Look for a missing check valve, a backward-installed valve, or a valve stuck partly open.
- If the outdoor discharge point is visible, make sure water is not blocked by ice, debris, or a crushed section of line.
Next move: If correcting a loose connection or replacing a bad check valve stops the pit from refilling, the pump should stop normal short cycling. If no backflow is present and the pump still runs with a dry pit, the fault is more likely in the switch or pump itself.
Step 5: Replace the confirmed failed part or call for pump replacement
By now you should know whether the problem is a stuck float, a failed sump pump float switch, a bad sump pump check valve, or an internal pump fault.
- If the float was only jammed, secure the cords so the float has a clear path and retest several cycles.
- If the external sump pump float switch is failed closed, replace it with a compatible switch style and route the cord so it cannot snag.
- If the sump pump check valve is leaking or installed backward, replace it and confirm the flow arrow points away from the pump.
- If the pump still runs with a free float and no backflow, plan on sump pump replacement rather than guessing at internal repairs.
- After the repair, run enough water into the pit to trigger at least two full cycles and watch for a clean start and stop each time.
A good result: The pump should start at the normal water level, empty the pit, and shut off without restarting on its own right away.
If not: If the pump still runs on with a dry pit after these checks, the safest next move is a service call and likely pump replacement.
What to conclude: You have moved from symptom chasing to a supported repair path. Do the confirmed fix, then verify the pump no longer runs dry or short cycles.
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FAQ
Why does my sump pump keep running when there is no water in the pit?
Most of the time the sump pump float switch is stuck up, tangled, or failed closed. Less often, the pump is cycling because water is falling back into the pit through a bad sump pump check valve.
Can a bad check valve make it seem like the sump pump never shuts off?
Yes. The pump may shut off normally, but if discharged water drops back into the pit, the water level rises again and the pump restarts. That can look like one nonstop problem when it is really repeated short cycling.
Should I replace the whole sump pump right away?
Not usually. Start with the float switch and check valve because those are common, visible failures. Replace the whole sump pump only after the float moves freely, the switch test fails or the pump has an internal fault, and backflow is ruled out.
Is it safe to let a sump pump run dry for a while?
No. A sump pump that runs dry can overheat and wear out fast. If you find it running with an empty pit, shut it off and diagnose the float or control problem before putting it back into service.
What if the pump only does this during storms?
Watch whether the pit is truly dry. During heavy rain, the pump may be working hard because water is entering quickly. If the pit empties and then refills from the discharge line, that points to backflow. If the pit stays dry and the pump still runs, that points back to the switch or pump controls.