Basement Sump Pump Not Working: Causes and How to Fix

A basement sump pump is important to avoid flooding, water damage, mold, and mildew. When it is not working, you want to fix it as soon as you can. But when your basement sump pump stops working, you also need to identify the causes before discovering how to fix it.

If your sump pump stops working, it could be caused by lack of power, clogs, or just being overwhelmed by being the wrong size or too old. To fix it, you will need to check the power supply, the float switch, check valve, and discharge line.

This article covers everything you need to know about sump pump failure and the things that cause it. It also includes what you should do if it happens and how you know when to replace the sump pump instead of repairing it.

Basement Sump Pump Not Working

What Happens if Your Sump Pump Fails?

A basement sump pump is important because it will prevent your basement from flooding. When a sump pump fails, especially during a thunderstorm, your basement is no longer protected against flooding and water intrusion.

Excessive water in the basement can cause several problems. It can impact your foundation or cause deterioration within the walls. It can lead to mildew and mold or even warp the wood and cause rot. These effects can lead to extensive and expensive repairs.

Because of this, sump pump failure can be a major problem. When it stops working, the water will pool, starting at the lowest point in the home. This is most likely the basement or crawlspace but could also be the foundation and other structural components.

When Should Sump Pump Turn On?

A sump pump is designed to turn on when the water level reaches a certain point. Once the water in the basin lifts the float switch above a designated level, the sump pump will kick on. If it does not kick on when water reaches this level, there may be a problem with the sump pump.

If you believe that the sump pump is not turning on when it is supposed to, you can test it with a bucket of water. Pour the water slowly around the sump pump. Once the water reaches the designated level, the sump pump should kick on. This level should be below the basement floor.

Furthermore, the sump pump should also switch off when the water level recedes below the designated level. However, depending on the location, the amount of rain, and other factors, the sump pump could kick on multiple times per day. If the sump pump is constantly running or kicks on too frequently, it will wear out sooner. It should never run too often and should never continue to run after the water level falls below the designated level and the float switch lowers.

Why do Sump Pumps Fail?

Sump pump not turning on

There are plenty of things that can cause a sump pump to fail. Let’s look at the different causes of sump pump failure so you can diagnose potential issues.

Electrical Power Outage

A loss of power is the most common cause of a sump pump failure. The bad thing is that this is often caused by a storm, which also brings the threat of flooding to the basement.

A sump pump requires power to run and will cut off as soon as you have an electrical power outage. Because of this, it is often a good idea to install a backup generator for the sump pump. This can help you avoid flooding if a storm does cause you to lose power.

Improper Installation

Improper installation is another possibility for sump pump failure, albeit a less likely one. The main errors that can occur during installation include the lack of a check valve on the discharge line and no air relief hole in the discharge line. A sump pump could also be installed on an insecure surface that can interfere with the float arm or switch.

Incorrectly Sized Pump

If you do not have the right sized sump pump, you could run into some problems, including complete failure. A sump pump needs to be the right size with the right amount of horsepower. If the sump pump is too big, this can cause it to wear out quickly because it can work too much. If the sump pump is too small, then it cannot effectively do the job. Either one can contribute to failure.

Product Defect

This is pretty unlikely, but by no means impossible. If a sump pump has a defect, it may fail to do its job or may not even run. After you install your sump pump, it is good to test it to make sure that it will run. You should also contact the manufacturer to get a refund or replacement.

Overwhelmed Pump

A pump can be overwhelmed if it is the wrong size, but it can also be overwhelmed by excessive or heavy rainfall and other factors. It is a good idea to take the horsepower of the sump pump into consideration to make sure that this does not happen. A ⅓ horsepower sump pump should manage 35 gallons per minute, but if this is not enough, you will want to get a higher horsepower to ensure that it does not become overwhelmed.

Stuck Switch

This is another very common reason for sump pump failure. This usually happens when the pump moves around in the basin. This will make the float switch become stuck or trapped against the pump because it is not level. If this is the case, you will want to adjust the sump pump’s position and take the necessary precautions to avoid the problem again in the future.

Frozen or Clogged Discharge Pipe

A sump pump’s discharge pipe is necessary to remove the water, but it can also be clogged with debris or frozen water. When this occurs, the sump pump will not remove the water and it will back up into your basement. It is hard to prevent freezing in some cold climates, but you can have a specialty line that allows water to escape even when the main discharge line becomes impeded by frozen water.

Float Switch is Not Working

A float switch may not work properly and if this happens, the sump pump may not ever switch on or off. It could be incorrectly configured or have debris or another blockage that can affect the float switch’s ability to function correctly. It is a good idea to maintain your sump pump regularly to avoid these types of problems and more.

Blocked Impeller

The impeller is necessary to push the water through the pipe, but it can become blocked or even damaged. When this happens, it may not be able to push the water as much as it should. This can cause flooding and make a sump pump largely ineffective.

How to Fix Sump Pump Not Working

How to Fix Sump Pump Not Working

To fix a sump pump that is not working properly, there are some things that you can do. However, what you can do depends greatly on the problem that exists.

Not Turning On

If a sump pump doesn’t turn on at all, then there are some relatively easy things you can try to get it to run again. This sometimes happens just because the sump pump is not getting the electricity that it needs to work. Other times, it is a problem with one or more of the mechanisms.

The first thing you should do is to make sure that the sump pump does have power. Make sure that it is plugged in and that the circuit is correct and complete. If you just had a power outage, you may have to reset the circuit breaker or the sump pump itself (you can see how to do so later in the article). You can also make sure that the outlet is working by plugging in another device.

If the sump pump is receiving power, then you will want to check some other components. Check the float switch to make sure that it is not stuck or blocked. If it cannot float properly when the water level rises, the sump pump won’t turn on. You can even lift the float yourself to ensure that the sump pump turns on when it reaches the designated level.

Next, try checking the impeller for clogs or other issues. To do this, you will want to unplug the sump pump and take the screen off of the bottom. This may have some debris that can block the impeller from rotating properly. Remove all the debris and try again to see if the sump pump will now run.

If none of the methods work and the sump pump still will not turn on, then you may be due for a replacement, especially if the sump pump is old.

Not Turning Off

While some people have problems with their sump pump not turning on, others have the opposite problem. When this happens, it can wear out your sump pump rapidly. This issue can have many problems, including defective parts, but the most common issues that can cause a continuously running sump pump are float switch issues.

When a float switch gets stuck in the on position, it will not move down as the water level recedes. Therefore, it will not tell the sump pump to stop. To check and fix this problem, you will have to open up the sump pump and look at the float switch.

Make sure that the float switch is not tangled or stuck and that it can move freely with the water. If it is not stuck, it could still be broken. If this is the case, you will need to buy a new float switch for your sump pump. It is not difficult to take the old float switch off and attach the new one. You just want to make sure that the new one will readily float up and down with the water level. Also, make sure that you tether the float switch with a zip tie.

Another cause of a sump pump that won’t go off is improper installation or change in the water table. If the sump pump is installed below the water table, then it may not ever turn off. For this problem, you will have to change the location or position of the sump pump.

Running but Not Pumping

If the sump pump is running but does not seem like it is pumping any water out, it isn’t going to work. This is often caused by a problem with the check valve, impeller, or discharge pipe.

First, you should examine the check valve to make sure it is not malfunctioning. The check valve should have an arrow or other mark on it to show the correct installation direction. However, if it is not installed correctly, it will not work or allow water to flow in the right direction.

A check valve may also be stuck closed. This is often an easy fix and could be caused by suction or debris. Manually opening the check valve, taking any debris out, and ensuring it can move easily often fixes the issue.

If the check valve wasn’t responsible, then you need to inspect the impeller. Make sure that there is no debris partially blocking the impeller. You also need to make sure that the blades are functional. This means that they should not be worn down, broken, or loose. If this is the case, then you need to get a new impeller.

Finally, a discharge line clog is the most likely problem with a running sump pump that does not withdraw the water. Remove any debris found and make sure that the discharge line will drain successfully. You should also scan the discharge pipe’s joints for leaks and repair them as needed. You can also check the intake screen on the bottom of the sump pump and remove debris blocking it.

Clogged With Mud

A clogged sump pump can develop a variety of problems and it is a good idea for any homeowner to know how to check for clogs and fix them when necessary. After unplugging the unit, you will have to remove the lid to access the basin. You may also need a flashlight to see far enough into the container.

Look at the area where the water enters the pump. This should be a small opening or screen. You may have to remove the pump out of the receptacle to see it in some cases. Remove any debris around the entrance cavity. Try to remove as much debris as possible from the basin. There may also be buildup on the walls that should be wiped away to prevent further issues in the future.

You may also want to check the bottom screen and impeller for other mud clumps that need to be removed. Check every crevice and component so that you don’t have to clean the mechanisms again shortly. After every portion is clean, you can reattach every part and test the pump by pouring 3 to 5 gallons in. If you cleared the mud, the water should flow directly through without impediment.

Discharge Line Underground Clogged

If the discharge line is clogged underground, you will have to use other methods to remove mud or debris. You will want to use a wet/dry shop vacuum m to remove all the water from the sump pump basin.

Remove the sump pump while making sure not to damage any components. You can then remove the drain pipe that is attached to the sump pump by loosening the clamps. This will provide access through the discharge pipe.

Use a plumber snake to push any large blockage and materials through the pipe. A hose can flush the pipe and clean other debris off of the walls and interior. It may require a high-pressure attachment to successfully clear away all the debris.

You can also shine a flashlight into the pipe to see if there is a significant blockage. If there is substantial blockage after the initial steps, you will have to repeat them until the pipe is fully clear. If you still cannot clear the discharge system, you may need to call a professional plumber.

After clearing the discharge pipe, you will want to test the sump pump and examine the drainpipe to the exterior of the home to ensure that the water will not exit too close to the house’s foundation.

What to Do if Sump Pump Stops Working?

Sump pump not turning on

When a sump pump stops working, then your first thought is probably to avoid flooding and other issues caused by excess water in the basement. However, you also need to keep safety concerns in mind.

A flooded basement can be very dangerous, especially if you do not take the necessary precautions. Never enter a flooded basement while power is still on. Before heading into the basement, make sure to turn the breaker completely off to avoid electrocution.

If you have a wet/dry vacuum on hand, you can also use it to remove any standing water in the basement or other areas. This can potentially save you from worsened damage or standing water that can cause mold and mildew before you can get a professional water damage company into the home. You can also open any windows to the basement to circulate air.

After taking these immediate steps, you can begin to inspect the reason for the sump pump failure.

How to Reset a Sump Pump

Your sump pump will probably have a reset button on the motor. If the sump pump isn’t running, especially after the power goes out and comes back on, this will often fix the problem by resetting the system’s action. However, if your model does not have a reset button, you can still reset it manually.

Find the switch to turn the sump pump off or unplug the sump pump. Either one will work for resetting the unit and to cycle the motor. If a power outage didn’t cause the failure, then this is when you should also fix any problems occurring within the sump pump.

Wait 30 seconds and then you can plug the sump pump back in and/or flip on the switch. If it still doesn’t turn on, then you may want to check the fuse box or breaker for any other issues or trips. If you still have a problem, the motor or switch could have a failed issue needing replacement.

How to Test a Sump Pump Float Switch Without Water

How to Test a Sump Pump Float Switch

There is a way to see if the float switch is working properly without water that does not test if it will float but will help you understand if there is a problem with the action or mechanism itself. It is a simple inspection that you can do quickly.

After you access the pit that includes the float switch, then the first thing to check to see is whether there is anything in the way of the movement of the float switch itself. If it cannot adequately move up and down, then it won’t be effective. If it is stuck, make sure to fix the problem that caused it to be stuck.

Now, while it is designed to move up and switch the sump pump on with water, you can just do it manually. This will help you check the configuration and you will be able to determine if the float switch will turn the sump pump on.

Just be careful when lifting it so that you do not damage the tether or other components. As soon as it reaches the right level, the sump pump should turn on. If not, then there is likely another problem at hand.

How Long Does A Sump Pump Last?

Typically, you can expect a sump pump to last around 10 years. Some will last longer than this, but older pumps are more likely to experience problems. Because of this, it is a good idea to replace them before they fail to make sure that your basement doesn’t flood.

Also, if the sump pump starts developing more issues after reaching 7 years old, then you should probably start thinking about replacing it. Sure, it may still last a few years, but you may be headed for frequent repairs or problems that can be avoided if you choose to replace it instead.

Under 7 years, or especially under 5 years, the sump pump is likely not failing due to old age. However, after 5 years or even 3 or 4 years, your sump pump will probably not be under any warranty. This is an important consideration to keep in mind and can help you decide if you want to think about getting a new sump pump.

How to Know When You Need a New Sump Pump

Repair a sump pump

Other than age, there are some signs that it may be near the end of life for your sump pump. Older sump pumps may have a hard time keeping up or running the way they used to. This may show up as weird sounds, vibrations, continuous running, or other issues. While these issues sometimes coexist with failure, they may begin to show up even when the sump pump is still running well. But that doesn’t always mean that you should not replace it because it could fail at a more inopportune time.

Other signs that it is time to replace your sump pump are visible rust, slow water removal, or turning off and on with the same water level. The motor also may start to sputter when turning on or off, which is a sign of imminent failure.

How Much Does Sump Pump Repair or Replacement Cost?

If you have a failing sump pump, you will have to decide if you want to repair it or get a new one altogether. Repairs can vastly range depending on the existing problem that occurs, but you can expect to at least pay a couple of hundred bucks if you plan on hiring a professional. If you are just repairing a part, it could be as little as $100 or even less, but on the high-end, repairs by a professional can cost over $500.

For replacement, you are looking at a total cost that could be substantially more. You can expect to pay at least $600 for a low horsepower sump pump but could easily pay well over $1000. For installation and a sump pump, you can expect to pay anywhere from $1000 to $2000 or more on the high end. If you plan to go this route, it is best to compare prices after determining the size and horsepower your basement will require.


A sump pump is an important piece of equipment that can prevent extensive damage to your basement and foundation. Without one, you risk flooding, mold, mildew, rot, and more. Because it is so important, it is a good idea to know what can go wrong and the factors that can contribute to failure so that you can reduce the likelihood of it malfunctioning during a rainstorm. It is also good to know how to fix it when you have to and many of the repairs are simple, even if you do not have sump pump experience.

Written By: Yevgen

YevgenI'm a DIY nut, and the founder and chief editor here at Weekend Builds.
This site is a result of my DIY passion, and to share the joys I have experienced fixing, building, and creating things over the years.

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