Sump Pump Running But Not Pumping

September 12, 2019October 28, 2020 Editor

Home-owners that had their fair share of sump pumps know that sump pumps can occasionally fail. Sump pumps are really good at stopping floods, but they are not that useful if they stop pumping water. Can you do something if your sump pump stops pumping, perhaps prevent it from ever happening?

Sump pumps will run but not pump for a number of reasons. Common causes are clogged lines, broken impeller, blocked float arm or the sump pump simply died. There are steps you can take to troubleshoot.

The best way to see what is wrong with your sump pump is by a process of elimination. From most common to least common.

Table of Contents

Reasons why your sump pump is not pumping water

There’s a couple of reasons why your sump pump could not be pumping water properly. Here are all those reasons:

The float arm is blocked or broken

As you may know, the sump pump is activated by a float arm. If your float arm is blocked by some object, that means that it can’t float and signal the sump pump that it needs to start. Your sump pump will also fail to start if the float arm is broken.

The check valve may be missing or is broken

This usually happens when you use a sump pump that the previous owner installed. A check valve needs to be installed on the discharge line to keep the water from flowing back. If the check valve is missing, water will flow back and cause the impeller to run in the opposite direction. If you are sure that you have a check valve, see if it’s intact.

Clogged discharge lines

If your sump pump is located where debris may get in it, there is a chance that your discharge lines will get clogged from dirt. When your discharge lines are clogged, water will not be able to flow and your sump pump can’t empty the sump pit.

Clogged discharge lines are pretty common, especially if not placed on a slight slope. Your discharge line can get clogged even if there is no debris in the sump pit. Discharge lines can have air holes, leaving an open space for dirt to get in.

Airlocked discharge line: no weep hole installed

Surprisingly many professionals forgot to drill a small weep hole beneath the check valve to allow air to escape that would otherwise build up underneith the check valve. When enough air builds up, this interrupts water flow completely and your pump won’t move water even if it’s pumping.

The weep hole should be drilled at a 45 degrees angle downwards and shouldn’t be too large.

Clogged inlet

The water in the sump pit first flows through the inlet of the sump pump, then it goes through the discharge lines. Your discharge lines can be clear, but clogging may occur in the inlet.

The reason for the clogged inlet line is the same as the one for clogged discharge lines. Your sump pump picks dirt along with the water, causing the inlet line to clog.

Ice blockage

During winter, freezing in the discharge lines is most common. If the sump pump picks up ice from the frozen sump pit water, the discharge lines or the inlet may freeze. Ice will clog the lines and the sump pump won’t pump.

Your lines can freeze even if there is no ice in the sump pit. If your discharge lines are not isolated or placed on a slope, most probably the lines will get clogged from ice.

Impeller not spinning

The impeller is a crucial part of the sump pump. The impeller is the source of the centrifugal force that the sump pump uses to suck water in. There is a screen in the sump pump that protects the impeller from getting jammed.

However, from time to time dirt gets through the protective screen. When this happens, the impeller gets jammed. Your sump pump will run, but the impeller will not turn. If your impeller does not spin, the sump pump can’t pump water.

The diameter of the discharge lines is too small

This is one of those problems that usually occurs when the previous house-owner bought the sump pump. Be sure to get the recommended discharge lines for the sump pump you bought.

If the diameter of the discharge lines is too small, it will significantly reduce the efficiency of the sump pump. Your sump pump will still pump, but the sump pit may fill faster than the lines discharge water.

Sump pump not working anymore

As I am sure you all know, sump pumps have an average lifetime of 3-10 years. There may not be a problem with any of the lines, but the motor of the sump pump will wear out after a certain amount of time. If your sump pump is running but not pumping, it may be a sign that you need a new one.

Troubleshooting

So, you are dealing with a sump pump that is running but not pumping. First, you need to identify the problem, then solve it. There are certain steps you need to take in order to identify the problem.

Inspecting the float arm

As I said, a blocked float arm is a common reason why sump pumps stop pumping. Checking if the float arm is working is easy.

First, unplug the sump pump. If there is a big amount of water in the sump pit, clear it out with a bucket. After that, check if the float arm is broken or blocked. If blocked, remove the object that is blocking it. If broken, replace the float arm with a new one.

Inspecting the valve check

If the float arm is okay, the next reasonable step you need to take is to inspect the valve check. If your valve check is missing, water will flow back into the sump pit.

When inspecting the sump pump, it’s best if you first unplug it. Usually, the valve check is placed on top of the sump pump or the beginning of the discharge line. Check if the valve check is intact and working properly.

If there is a problem with the valve check, it’s best to replace it. If not, you can move on.

Checking for clogging in discharge and inlet lines

Once you eliminated the usual suspects, it’s time to see if your lines are clogged. As always, plug the sump pump off.

Start with the discharge line, go outside at the end of the discharge line. Check if there is any blockage near the end of the discharge line. If there is any debris, clean it with your hand using a rubber glove. You may need to use a screwdriver or a coat hanger if the blockage is big enough.

If there is no problem with the discharge line, move on to the inlet line. Make sure your sump pump is unplugged. Remove the sump pump, and inspect the inlet line. If there is any blockage, clean it thoroughly.

You can pour water in the disconnected discharge line so you can check if there is any blockage in the middle of the line. If debris is not clogging the lines, but ice is, you can unfreeze the lines by pouring hot water in them.

Inspecting the impeller

Once you went through the easily accessible parts and made sure that everything works well, it’s time for the impeller. Again, unplug the sump pump and disconnect the discharge lines.

In order to inspect the impeller, you must remove the sump pump from the sump pit. With some models, you have to remove the bottom casing in order to reach the impeller. Check if the impeller is damaged.

Often, you can repair the impeller, but sometimes you will need to replace it. Either way, make sure to clean any debris around the impeller.

If the impeller fell off, and there isn’t any damage, you can put it back on. Don’t thread the impeller all the way, give it a spin after you are done. When the sump pump turns back on, it will tighten the impeller itself.

If you can’t repair the impeller, you will need to buy a new one, suitable for your sump pump. You can find replacement kits (affiliate link) for most brands online or you can order them through a local store.

Make sure the sump pump was installed properly

If your sump pump is running but not pumping, and that is the reason why you are noticing your sump pump for the first time, you will want to see if it’s installed correctly.

First, see what kind of a sump pump you have. Find out what kind of discharge lines you need for that model. Measure the diameter of your discharge lines to see if they match the instructions.

If your discharge lines are too small, your sump pump will not function efficiently. Make sure to replace your discharge lines, if you are dealing with this problem.

Is your sump pump near its death?

If you have eliminated every other problem, unfortunately, you will need to get a new sump pump. Your sump pump will not work without its motor, even if every other part is working okay.

Before jumping to this conclusion, make sure that there really isn’t a problem with the rest of the sump pump.

If your sump pump truly is dead, I highly recommend buying a high-quality sump pump. It may cost you more, but you will be peaceful for the next 5-10 years. Here’s a hand picked list of 10 quality sump pumps that we really like.

How to clean and maintain your sump pump

Even though sump pumps die from aging, there is something you can do to make sure it lasts as long as it can. As every unit in your house, the sump pump must be cleaned once in a while. The use of glove hands is recommended.

Cleaning your sump pump will not only prolong its life but significantly enhance its performance. The debris may not clog the sump pump but decrease its efficiency. Cleaning your sump pump saves you money.

When you are cleaning your sump pump, make sure its plugged off and the discharge line is disconnected. Then, you will need to remove the sump pump from the sump pit. Beware, the sump pump may be wet, so take precautions.

While disconnecting the discharge line, be sure to clean the valve check. Remove any dirt that may prevent it from doing its job. Check the float arm to see if there is anything that blocks it from doing its job.

Vinegar is quite an efficient cleaning agent for cleaning debris in your sump pit.

Then, you can move on to cleaning the sump pump. Wipe the outside of the sump pump so you can see better.

Before you move on to the impeller, make sure that the inlet line is clean. Once you are done with the inlet line, clean the screen protecting the impeller. Then, you can inspect the impeller for any damage or blockage.

If your sump pump looks kind of rusty, check the manual to see if you can put some oil on it. If everything is okay, you can move on to the sump pit.

Before putting the sump pump back, you need to clean the sump pit from any dirt that may get in the sump pump. Check the bottom and the walls.

If you have done everything, it’s time to put the sump pump back in. I highly recommended cleaning your sump pump from time to time. If you are lazy, pay a professional to do it.

In conclusion, that is everything you need if your sump pump is running but not pumping. Unfortunately, this problem sometimes ends in you buying a new sump pump. Don’t let that discourage you from giving your sump pump the maintenance it needs.