Home Improvement

What Does “Pump Overrun” Mean?

Picture this – it’s a cold winter day, your boiler has been working hard to keep your home warm and cosy. It has achieved its goal and is ready to shut down. However, you notice that the pump is still running. You check your boiler and see it displaying the “pump overrun” code. Is it an error? What does it mean?

There’s no need to worry! This is a perfectly normal part of some boilers’ heating cycle. In this article, we will go over and answer the question “what does pump overrun mean on a boiler?” and hopefully put your mind at ease!

Table of Contents:

So, if you:

  • Are wondering what “pump overrun” means on your boiler;
  • Want to know what this feature does;
  • Are having issues with your pump running all the time,

Then keep reading! This article will answer your questions.

What is “pump overrun”?

Pump overrun is a normal function of your boiler. If your system has this feature, it will usually come on after heating or hot water has been used. Its purpose is to dissipate any residual heat to avoid damage to your boiler’s components.

When pump overrun is on, your pump keeps running for a short time, usually 5-10 minutes. This function is controlled by either a pump overrun thermostat, keeping it on until a certain temperature is reached, or a timer, running for a set amount of time.

The hot water in your system goes through a bypass valve and circulates until the heat dissipates. This reduces the risk of water boiling inside the boiler and damaging its parts. Depending on whether you have an S-plan or a Y-plan heating system, you may need to have a bypass circuit piped in.

Some larger, sturdier boilers are specifically designed to cope with the residual heat, thus they have no need for such a feature.

Why does my central heating pump keep running?

Pump overrun should only last about 5-10 minutes, or until the heat dissipates. If the pump is running for hours on end, or constantly, there may be an issue with the system. Possible causes are a faulty pump overrun thermostat or timer, or a damaged PCB (Pump Circuit Board).

If there are issues with your boiler, you need a Gas Safe registered engineer to handle the repairs. The technician will be able to diagnose the problem and will know how to safely deal with it. Do not attempt to fix the issue yourself, as this can pose a risk to your home and health.

Is your boiler in need of repair?

Let the professionals handle the work! Fantastic Services offers a reliable boiler repair service, performed by certified and Gas Safe registered engineers. They will come with all the tools and skills necessary to complete the repairs. The technicians can deal with any brand and type of boiler for your convenience. You will even get a 12-month guarantee on the parts and the performed work! Sit back and relax, knowing that your boiler is in safe hands. If you want to be sure that you’ll have a certified professional to maintain and repair your heating system when the need arises, opt for the boiler cover plan.

Keep your heating system safe and functional! Find out about our boiler repair service here.


  • Pump overrun is a normal function of a heating system.
  • After the boiler has been switched off, the pump circulates the water to dissipate any residual heat.
  • Some boilers don’t need pump overrun, as they are designed to handle the heat.
  • Pump overrun should last 5-10 min, or until the water cools down enough.
  • If your pump runs for hours after the boiler has been turned off, there may be an issue in the system.
  • Always rely on Gas Safe registered engineers to handle boiler repairs.


Did you find this article useful? Did we miss anything? Let us know in the comments below!

Image source: shutterstock / steved_np3

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