Little Giant Pump Humming But Not Working

Little Giant Pump Humming But Not Working

Your Little Giant Pump humming but not working? If this is the issue you are experiencing with your sump pump, the following culprits are to blame, including: 

  • Check valve is installed backwards or incorrectly
  • Check valve gets stuck or plugged
  •  The lift you set up for the pump is too high
  • A clogged impeller
  • Pump Is Air Locked 

The sump pump won’t discharge though it makes a hum unless you resolve those issues. And luckily, I will take you through every troubleshooting step you need to take to bring your Little Giant into working condition. 

So, keep reading… 

Table of Contents

Why Is My Little Giant Pump Humming But Not Working?

Generally, Little Giant Pump makes a humming noise but it won’t work or move water if you install the check valve improperly or the impeller gets clogged. Turns out, pump airlock issues can prevent the unit from working while it’s still humming. 

Below, I will break down each of those issues and walk you through the troubleshooting steps to resolve them. 

1. Check Valve Is Installed Backwards

A check valve prevents the backflow of water into the sump. That’s the key to installing a check valve in the discharge line. 

If you or your plumber install the check valve incorrectly, it will not serve its purpose, aka ‘prevent the backflow of water.’

Consequently, your sump pump fails to move water from the sump while it’s running. 

How To Fix: 

Check the installation of the check valve and ensure your plumber installs the check valve in the right direction. Just follow the flow indicating arrow on the check valve body to verify it’s installed properly.   

2. A Stuck or Plugged Check Valve

You already know the purpose of installing a check valve in the discharge line on your sump pump. 

But the check valve fails to work or prevents the backflow of water if it gets clogged by dirt & debris.  

How To Fix: 

To begin with, remove the check valve from the discharge pipe and inspect it for proper operation. If it gets plugged, replace the check valve with a new one and install it properly. 

3. The Lift Is Too High For The Pump

Little Giant Sump Pump will just make a hum but fail to dewater your crawl spaces or basements if the lift height is beyond the pump capacity. In the worst case, your pump won’t move a single drop of water if the lift height is too high for the pump. 

How To Fix: 

I recommend you check the rating table to set the lift height according to the pump’s capacity. 

Based on the model of Little Giant Pump, the performance of the pump you own can be different. For example, if you have 6-Series Sump Pump from Little Giant, the performance graph will be like this: 

Little Giant 6-Series Sump Pump Performance Graph
Credit: Little Giant

4. Impeller Gets Clogged

The impeller is the component that is responsible for moving water from the sump. If it doesn’t work due to restriction, the unit won’t dewater the sump pit. 

However, you can easily bring the unit back into working condition by releasing the obstructions from the impeller. In the ‘How To Fix’ section, I will show you how to clean the impeller on Little Giant Pump. 

How To Fix:

To clean the impeller on your Little Giant Sump Pump, follow the below instructions: 

1. Disconnect the pump from electrical power and remove the discharge hose from the pump. 

Removing the discharge hose from the pump

2. Remove the screen by prying apart the slots between the screen and the volute. 

Removing the screen

3. Unscrew the screws that hold the volute to the motor housing and remove the volute from the bottom of the unit. 

4. Now, clean the impeller and the volute passage. You can use a cleaning solution of dish soap and water rather than strong solvents. Once you clean the impeller, ensure it’s moving freely by rotating it by your hands. 

Cleaning the impeller and the volute passage

5. Replace the seal ring into the volute and secure the volute to the motor housing with screws. Finally, replace the screen onto the volute. 

5. Pump Is Airlocked

In the event of pump airlock, the unit will run but fail to remove water from the sump pit. 

To prevent the airlock issue, I recommend you drill a relief hole in the discharge pipe. The hole should be located below the floor line between the discharge line and the check valve. 

For better understanding, watch this tutorial to learn more about pump airlock and the way you can prevent this issue: 


A humming noise coming from the sump pump indicates the pump is running. If you hear that noise but the unit is not pumping water, I bet your plumber installed the check valve improperly or it gets plugged. 

Apart from those, too high lift, clogged impeller, and pump airlock are other common reasons that cause the unit to not pump water. 

Fortunately, I mentioned troubleshooting steps to resolve those issues. So, follow the prescribed remedy and bring the unit back into working condition. 

Happy Plumbing!

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