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Why Is My Sump Pump Constantly Running?

Troubleshooting from George Brazil


A sump pump that runs non-stop is problematic because it will:

  • Eat up a lot of energy
  • Overheat and require constant repairs
  • Have a much shorter lifespan

So what’s causing this? Well, it depends on the situation:

If your sump pump runs non-stop and struggles to pump out water, you likely have one of the following problems:

  • Undersized sump pump
  • Clogged intake screen
  • Leaking discharge line
  • Faulty check valve
  • Faulty impeller

But if you have a sump pump that runs continuously when there’s no water present, the most likely problem is a stuck float switch.

We’ll explain these problems in more detail and what you can do to stop your sump pump from overuse.

Need a professional’s help? Just contact us and we’ll send over a plumber right away.

If your sump pump runs non-stop and struggles to get rid of water…

…you probably have one of these 5 problems:

Problem #1: Undersized sump pump

If your sump pump is too small, your system will have trouble pumping water out of the pit as quickly as water is coming in. And when that happens, your sump pump will run much longer than it should.

You see, sump pumps are sized according to how many gallons of water per hour (GPH) they can pump out of the sump pit. The higher the GPH, the faster the device can pump out water.

What to do: 
First, you’ll want to determine if your sump pump might be too small.

Two ways to do that include:

1. Calculate your sump pump capacity needs. Follow the 3 steps below. If the GPH you’ve calculated is higher than the GPH of the sump pump you currently have, you most likely need to upgrade to a sump pump with a higher pumping capacity.

Note: the steps below only offer rule-of-thumb calculations. Only a professional plumber can offer precise sump pump measurements.

  1. On a rainy day, run your sump pump until the water recedes to the shutoff level. Wait 1 minute (pump turned off) then measure how far the water rose.
  2. Every inch of water inside the pit amounts to approximately 1 gallon. Multiply the number of inches that the water rose in that minute by 60. This number is the volume of water that would come into your pit during an hour of steady rain.
  3. Multiply this number by a “safety factor” of 1.5 to figure out the pumping capacity you would need.

2. Visually inspect your sump pump’s performance. If you notice that the water inside the pit is not rising and falling on a regular basis (like in this video), have a professional inspect the system to ensure that your sump pump is sized correctly.

Problem #2: Clogged inlet screen

Once a sump pump is activated, water is pulled into the pump via a motor. And depending on the design of your sump pump, that water might have to pass through an “inlet screen” that prevents solids from jamming up the motor.

But the screen itself often gets clogged with dirt or debris. And when that happens, the sump pump can’t pull in and pump out as much water. Which means your sump pump will run continuously as it struggles to get rid of the water.

What to do:

  1. Turn off power to your sump pump and lift it out of the sump pit.
  2. Use a flashlight to inspect the screen for debris.
  3. Use a toothbrush to brush away dirt and debris or use a hose to gently clear off the screen.
  4. Plug the sump pump back into the outlet and lower it into the pit. If the sump pump still runs continuously and can’t clear water from the pit, have a professional inspect the unit.

Problem #3: Leaking discharge line

Your sump pump’s discharge line is responsible for carrying water outside and away from your home.

Discharge pipes are usually made of PVC piping, which, over time, suffer from normal wear and tear, resulting in leaks along the line. And if those leaks gradually get bigger, water won’t make it outside. Instead, it will drip out along the line and right back to the sump pump pit. Which means your sump pump will run non-stop as it tries to empty the pit.

What to do:
Visually inspect the discharge line. If you see any cracks or see water dripping back down along the line, have a professional replace the discharge line.

Problem #4: Faulty check valve

Within the discharge line is the “check valve”, a device that ensures that no water can flow backwards into the sump pit.

But if the valve is clogged or has gone bad, water will rush right back into the pit, forcing your sump pump to work constantly with no results.

What to do:
If you’re handy and have experience working on sump pumps, you can remove the pipe over the check valve with a screwdriver. Once it’s removed, you can inspect the valve and remove any debris that may be blocking the valve.

Otherwise, you’ll want to have a professional inspect your check valve to determine if it needs to be repaired or replaced.

Problem #5: Faulty impeller

A sump pump impeller is a motorized fan-like device that draws water into the pump as it spins. The spinning motion of the impeller also helps to push that water up through the discharge pipe.

However, if the impeller is clogged or needs to be replaced, the sump pump will continue to run without successfully pulling in and pumping out water.

What to do:
Have a professional inspect your impeller to determine if it needs to be repaired or replaced.

If your sump pump runs non-stop and there’s no water…

…you likely have a float switch that’s stuck in the ON position.

You see, during normal operation, your sump pump is turned on and off by a “float switch”. On most sump pump models, the float switch is basically a buoyant ball that “floats” up as the water level in the sump pump pit rises. The float switch is connected to a lever that switches the sump pump on and off.

So as the float switch rises up, it eventually turns the sump pump on. As the water is pumped out and the water level drops, the float switch also drops, turning the sump pump off.

But if the float switch is permanently stuck in the ON position, it will force the sump pump to run non-stop, even if there’s no water to pump out.

What to do: 

  1. Unplug the sump pump. Most sump pumps are plugged into a nearby outlet. Unplugging the sump pump will stop the device from operating, allowing you to inspect the float assembly.
  2. Clear the sump pit. Obstacles such as rocks or dirt can prevent the switch from lowering.
  3. Make sure the float moves up and down freely. To do this, manually lift and lower the float. Depending on the type of pump you have, your float may move vertically up and down a rod or it may float freely up and down (like in the picture above). Either way, make sure that it can move unobstructed to the bottom of the pit.
  4. Move the sump pump to the center of the pit. Over time, the vibration of the sump pump motor can cause it to move and sometimes, it can pin the float switch against the sump pump liner.
  5. Plug the sump pump back in to see if it still runs constantly. If it does, you’ll need to have a professional inspect the system as you may need to replace the float switch altogether.

Sump pump still running non-stop? Ask an AZ Plumber

If you’re still having problems with a continuously running sump pump, we can help.

Just contact us and we’ll send over an experienced plumber right away.

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