Grundfos MQ3-45 Leaking From Bottom: Reasons And Troubleshooting

The Grundfos MQ3-45 is a well-known pump for its reliable quality. However, there is one issue here. There are several complaints about Grundfos MQ3-45 leaking from the bottom.

Now, why does this happen, and how can you fix that?

Here, I will be diving deep into all the reasons that cause this problem and try to give you the solutions to those causes as well. So, if you are using this pump, you will surely get something out of this whole discussion.

Reasons For The Pump Leaking From Bottom

Grundfos MQ3-45

Knowing the reasons for this pump leaking from the bottom is important. Unless you know the reasons for this problem to happen, you can’t solve the problem. So, let’s check them out first.

  • External Damages To The Pump

One of the most common reasons for your Grundfos MQ3-45 to leak is any kind of external damage to the pump. A lot of the time, the pump can get damaged from too much pressure or something hitting the outer part of the pump.

When there is damage to the bottom part of your pump, it can easily start leaking from there. How the pump gets damaged isn’t easy to determine, so you just have to keep an eye out for it.

  • Worn Out Seals Or Gasket

Another popular reason for this pump to leak from the bottom is because of a damaged or worn-out shaft seal. The shaft seal keeps the pump protected from any kind of water leaking through it.

The seals are placed on the motor shaft, so you have to check there to find whether the seals are okay or not.

The reason for the seals to wear out or damage most of the time is an increase in temperature. When the motor shaft gets too hot, it slowly eats out on the shaft seal.

And at some point, you will face leaking issues on your pump bottom.

  • Faulty Foot Valve

Even though this doesn’t happen that often, you will find that the foot valve on your Grundfos MQ3-45 valve is damaged. The valve is responsible for controlling the water flowing through.

So, when it gets damaged, it can easily cause leaking issues from the bottom.

Keep in mind that the foot valve is a bit different from the check valve. So, it’s important to figure out which one is causing the leaking problem.

  • Corrosion

Corrosion is another reason that can easily damage the bottom part of the pump and cause it to leak. However, it doesn’t happen too much or isn’t that common, so you won’t have to worry about this causing any kind of leaking that often.

But if something else isn’t causing it, then I would say its corrosion that’s doing it.

Well, aside from these, I don’t think there is anything that can cause the pump to leak from the bottom. Now, remember, I am talking about the pump leaking from the bottom and not air leaking inside.

That’s an entirely different issue that is also brought to light quite a lot.

Solutions For The Pump To Leak From The Bottom

When it’s about the solutions to these problems, I would say there are some things that you can do about it. However, for the most part, replacement seems to be a more viable option than repair with these problems.

So, let’s check out the solutions you can try to fix them.

  • Repair The External Damage To The Pump
troubleshooting Grundfos MQ3-45

Here’s the thing, this is subjective to how much damage it has suffered.

If the damage to the pump is too much, you might not be able to repair it.

In that scenario, the only option you have is to replace the whole pump.

However, if the damage isn’t that much, you can easily use any kind of adjustment or sealant to seal off the leaks.

So, if you have any leaks because of external damages, just look for a sealant that can seal the leaks on your metal pump.

  • Replacing The Seals

Unlike the other one, the solution is only to replace the shaft seal. There is a complete kit you can find out there for the shaft seal of this pump.

Fortunately, it’s readily available on Amazon and other online stores as well. So, you can easily get the kit for your needs.

Before you go ahead and get the shaft seal kit, you have to make sure that you are getting the proper size. Also, the quality of the seal kit has to be top-notch.

Otherwise, you just face the same leaking issues even after replacing the seal.

  • Getting A Replacement Valve

Now, when you have a faulty foot valve, there is hardly any way to repair that part. So, the only option for you is to replace the valve with a new one.

You can find them from the dealer or a hardware store.

Once you get the replacement valve, you can either install the replacement valve yourself or rely on professional services to get the job done. I would say it’s preferable to go for an experienced mechanic to get it fixed.

Typically, these are the solutions you can try out for these problems. As for the corrosion issue, I don’t think there is anything you can do about it.

You can surely try out general solutions to fix corrosion, but whether that will work or not doesn’t have certainty.


In short, the Grundfos MQ3-45 leaking from the bottom is something that you will come across at some point. Most of the time, the reason for this issue is the shaft seal getting damaged.

That’s the part that is most concerning about this pump.

To ensure you have a solution to that, you can simply get the shaft seal replacement kit from various sources. You have to get the shaft seal kit and install it in your pump system.

You can do it yourself or simply get a professional to replace it for you.

Ralph Wade

Hey...Ralph is here! So, did you find this article useful? If so, please leave a comment and let me know. If not, please tell me how I can improve this article. Your feedback is always appreciated. Take love :)

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