Boiler Pump Not Working Causes And How To Fix It

James Elston
Written by James Elston
Updated on 4th December 2023
Posted on 3rd December 2023
Topic: Boiler Guides
Boiler Pump Not Working Causes And How To Fix It

Boiler pump not working? here are the causes and how to fix a broken pump

worcester 4000 boiler

A dreaded central heating system failure is not always an indication that you need a new boiler. Sometimes heating issues are simply a result of a problem with the boiler pump, a key component of your boiler system.

Whether your central heating has stopped working or you’re concerned it may be about to, it is worth ruling about whether the pump is the root of the problem or you need a new boiler.

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You may already suspect that your boiler pump is not working correctly and want some assistance in identifying and remedying any pump problems. If you’ve never handled a boiler pump before, it may seem like a daunting task, but in a lot of cases, rectifying boiler pump problems are surprisingly straightforward.

To help you identify the issue and decide whether this is a problem you can resolve yourself without the expense of an engineer, we’ve put together this handy guide. if you can’t fix it and you are considering a new boiler, you can get a fixed price online now for full boiler installation, which may save you money in the long run

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How do I know if my boiler pump is not working?

Common indicators of a non-functional boiler pump are poor heating, leaks, strange boiler pump noises coming from your boiler, and cold pipes, which you may have already noticed.

In this guide, we’ll highlight common signs that your boiler pump is not working and explain how to diagnose issues such as incorrect flow rate settings, blockages, and issues with the power supply. While we explain how you can repair common boiler pump issues yourself, in some instances, you may need the help of an engineer or a boiler pump replacement.

What is a boiler pump?

Broken boiler pump

Inside your boiler, there is a pump that is sometimes referred to as either a central heating pump, circulator pump or boiler pump.

Within the central heating system, the pump’s function is to circulate hot water from your boiler, through the pipes and throughout your home to supply your radiators, taps, and showers.

When a boiler pump stops working properly it can cause issues for the entire central heating system.

Where is my boiler pump located?

Before you can do any sort of troubleshooting you need to find your boiler pump.

Circulating pumps are usually located inside or near your boiler, especially in combi boiler systems. Alternatively, it may be located in an airing cupboard next to the hot water cylinder, as is typical of non-combi systems.

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Common indicators that your boiler pump is not working

It doesn’t take an expert to determine whether your boiler pump is not working correctly. There are many indicators and signs that are easy to notice and assess yourself.

If your central heating system displays any of the indicators listed, it is highly likely the issue lies with your boiler pump, rather than the boiler itself.

noisy boiler image

Common indicators your pump is not working correctly:

  • Unusual noises coming from the boiler such as a constant hum
  • The pump is running but the water flow pipe is cold
  • Water is leaking from the pump
  • The pump casing feels unusually hot to touch
  • There is no hot water from your boiler
  • Your pump is constantly running and won’t switch off
  • The boiler pump is not working at all (no vibration or heat)
  • Poor heating – taking longer than usual to heat or not heating to full temperature. Or not all of the radiators are heating up

Many of these signs of malfunction are caused by problems that can be quite easily resolved and fixed, such as trapped air or a build-up of debris in the boiler pump.

Don’t replace the pump until you’ve ruled out a potential repair first. Check out our boiler pump troubleshooting guide below to diagnose the issue and learn how to repair the pump where possible.

Boiler pump troubleshooting guide

Problem: Water is not circulating around the system, but the pump is on

How to identify it:

The first indication of this issue would be a lack of hot water coming from your taps and cold radiators – this tells you hot water is not circulating around your central heating system.

water temperature

You can determine whether your pump has power by placing your hand on the pump. If your pump is slightly warm to the touch and vibrating, then your pump is on.

If your pump does not seem to have power, see the ‘no power in the pump’ section below.

What is causing it?

If your pump is running, but no water is moving around the system, the issue is likely a jammed shaft or propeller. Usually, this is caused by the presence of debris within the system.

How to fix it:

Try tapping the pump gently – this may be enough to free the shaft/propeller. If this does not resolve the problem, you will need to call an engineer to assist you. To prevent this problem from reoccurring, ensure you are having your boiler serviced annually.

Problem: No power in the pump

How to identify it:

To determine whether your pump is working, gently place your hand on the pump. You should feel aslight vibration and the pump should be warm to the touch if it has power.

gas safe logo

What is causing it?

If your boiler has power, but your pump does not, it could be due to an issue with the wiring or the fuse.

If your boiler doesn’t have any power at all, then this is likely due to the PCB unit rather than the pump.

How to fix it:

You will need to call a Gas Safe heating engineer to come out and check the wiring for you. They may be able to fix the wiring or fit a new fuse, or if the pump is old they may opt to replace the pump completely.

Problem: Circulator pump is noisy

How to identify it:

If you can hear strange sounds and you think they may be coming from your boiler pump, first locate the pump to ensure that it is definitely the source of the sound. Then simply listen to the sound your pump is making to identify whether the noise is louder or different to usual.

What is causing it?

If you find your pump is rather noisy, an airlock may have formed inside the pump. Typically, people often complain of a constant humming noise when an airlock has formed in the pump. Trapped air can cause your pump to stop working, so ensure you act if your pump is making a racket.

How to fix it:

screwdriver and spanners

This problem has a relatively simple solution. You just need to release some air by adjusting the bleed screw. All you will need is a flathead screwdriver and a cloth or towel.

For a pump that’s located outside of your boiler, follow these instructions:

  1. Ensure you have switched off the electrical supply to the pump before you begin
  2. Locate the small bleed screw on the pump – you may need to check the boiler’s manual
  3. Place a cloth or towel underneath the screw, to absorb any water that may leak out
  4. Turn the screw very slightly, very slowly, to allow any trapped air to escape
  5. Retighten the screw and turn the electrical supply back on

If this doesn’t stop the noise, a bearing within the pump may have come loose, in which case, you’d need a new pump.

Problem: Blocked pump

How to identify it:

The first sign of a blocked pump is that the radiators are not heating sufficiently or at all, or there is a lack of hot water, despite your boiler and pump both having power.

humbs down

You can try to rule out other potential causes such as a jammed shaft/propeller by tapping the pump to unjam it, or by listening for rattling and clicking, which would rule out a broken impeller.

What is causing it?

If your radiators are not heating sufficiently or at all, the circulating pump may be blocked, or it may have stopped working entirely.

Blocked pumps occur due to a build-up of sludge and debris collecting within the pump, affecting its performance and will eventually cause the pump to fail.

How to fix it:

It may be possible to clear the blockage yourself but we would recommend calling a Gas Safe engineer to diagnose the issue and perform a system cleanse if needed. Having an annual service will also help to prevent this from occurring.

Once the system has been flushed and the pump has been cleaned, you may wish to have a magnetic system filter fitted to prevent it from happening again, or to clean your boiler more regularly, to prevent the grime from building up again in future.

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Problem: Leaking pump

How to identify it:

You may have noticed water leaking from your boiler or pump or a puddle forming beneath it.

What is causing it?

If water is leaking from your circulating pump then it is likely a sign that either the pump has become loose, or the seal needs replacing.

Alternatively, the pump body may have corroded, which is usually due to age or inactivity of the system.

If your central heating system has been switched off all summer, you may find problems such as this when you turn it back on when the cold weather comes back around – this is one of the reasons why it is recommended for you to switch on your heating periodically, even in summer.

How to fix it:

The solution depends on the issue here. To see if the pump has simply become loose, simply tighten up all the joints. Then check the joint of the pump – if this is the source of the leak, the seal may have blown in which case you can call an engineer who may be able to just replace the seal, but may need to replace the entire pump if it is particularly old.

If it’s still leaking and you’ve ruled out the seal and a loose pump, check the pump over to see if any parts have corroded. A corroded pump will need to be replaced.

Problem: Incorrect speed and flow rate settings

How to identify it:

If your radiators are not heating correctly this could be an indicator of incorrect speed and flow rate settings. Identifying that this is the cause yourself can only really be done by ruling out the other pump problems explored in this guide, or by adjusting the settings to see if an improvement is made, but this is not always advised so it may be wise to get a boiler engineer to diagnose the issue instead.

What is causing it?

Some pumps have adjustable speed and flow settings, especially newer models. When these settings are set incorrectly it can cause issues with your radiators heating properly.

The settings are usually between 1 and 3, with 1 being the slowest flow rate and 3 the highest. Having a pump set to the wrong settings will naturally affect its functionality.

How to fix it:

You may need to contact an engineer to diagnose and fix the problem for you, or you can attempt to adjust these yourself.

The switch will be located on the top of the pump. If it is set to 1 or 2, the flow rate may be too low and turning it up may resolve it. However, some systems may not cope with a flow rate of 3 and the pump may have been intentionally switched to the lower rate, in which case turning it up could compromise the boiler and cause it to break or leak, so it is probably worth at least calling an engineer for their advice.

Problem: Incorrect installation

How to identify it:

Your pump has not been working since day one and you’ve had no heating or hot water since it was installed.

What is causing it?

This is relatively rare, but sometimes a faulty pump can simply be due to human error and incorrect installation, such as being fitted the wrong way round. If your pump has never worked, then this is likely the cause.

Alternatively, there is a chance that it was installed correctly but is genuinely faulty.

How to fix it:

The pump will need to be removed and refitted correctly – you will need an engineer for this task. If it was incorrectly fitted in the first place, then contact whichever engineer installed it, as they should redo it for free.

Problem: Pump constantly running

How to identify it:

Boiler pumps typically kick in when you demand heat or hot water and continue to run for some time after, but you may have noticed that yours always seems to be on. To determine whether there is an issue, check when your boiler is not being used to see if the pump is running when it shouldn’t be.

What is causing it?

If your pump is constantly running and won’t switch off, this could be due to a number of reasons: a faulty PCB (circuit board), a faulty pump overrun stat, or the mid position valve is stuck.

How to fix it:

If the issue is due to the valve sticking, simply use WD40 to lubricate the valve.

For a faulty PCB or pump overrun stat, call out an engineer to have these fixed.

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Problem: Pump shaft has seized

How to identify it:

When a pump shaft seizes, the first sign is no heating or hot water. If you place your hand on the pump and it feels hot rather than slightly warm then this may also indicate a seized pump.

To determine whether your pump shaft has seized or not, first locate the pump shaft. You may need to remove a panel to access it.

You should be able to see a small slot at the end of the pump shaft. Insert a small flathead screwdriver into the slot and attempt to turn it. It should turn without much resistance, but if you are unable to turn it then your pump shaft has seized.

What is causing it?

Pump shafts can seize for a number of reasons, from lack of use, components rubbing together or foreign objects entering the pump, to name but a few.

How to fix it: You’ll need to replace the pump if the shaft is seized.

Problem: Broken impeller

How to identify it:

The pump impeller can break and this is usually easy to diagnose. Listen to the pump, if you hear rattling or clicking noises this is due to the loose fragments of the impeller moving around within the pump.

What is causing it?

The impeller has broken – this could be due to age, excessive use and stress or a foreign object within the pump.

How to fix it: You will need to replace the pump. See below for guidance on pump replacements.

If you need a new boiler pump

Should you need to replace the pump, check your warranty before you purchase a new boiler pump. Usually, if the pump is less than 5 years old you’ll be entitled to a free replacement. If not and you do need a new one, take a look at the best central heating pumps available in the UK to buy.

Circulating pumps vary in price, and the cost of your replacement will depend on the brand and type of pump, and how straightforward the installation of the pump will be. if you hve an older boiler, get a free boiler quote, it may cost you less in the long run.

Average cost for a new pump will typically be between £90 and £160, with labour costs pushing this up to £150-350. The average new boiler cost is around £2,000, but you can get boilers for around £1,600 if you have a lower budget.

To determine what replacement boiler pump you need, inspect your old pump for specifications such as speed and flow rate or a model number.

If you are having issues with your pump repeatedly, or find yourself having to change the pump regularly, then there could be an underlying issue with your boiler itself. With Boiler Central you can get a new boiler priced up in minutes. You can also spread the cost with boiler finance in an emergency.

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Written by
James Elston
James Elston Director Of Boiler Central
Posted on: 3rd December 2023
Topic: Boiler Guides

James Elston is our resident boiler replacement and heating expert here at Boiler Central. With over 20 years experience in the boiler installation industry, James ensures that he knows everything there is about our Gas Safe boiler installations, energy saving and home heating solutions. This can be from simply procuring the latest best combi boilers, to reviewing and ensuring that Boiler Central maintains the highest standards across our boiler installation company.

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