The 8 Most Common Central Heating Pump Problems [And Fixes]

Alot of boiler issues stem from central heating pump problems. This can include a range of faults including leaks, noisy boilers, or even radiators not working.

If you have any questions relating to heating pump problems, please leave a comment below and we’ll get back to you.

You can also get a free quote and advice from engineers by filling out this boiler pump repair quote form.

Sick of your unreliable and expensive-to-repair boiler? Get a fixed price online from BOXT, a company part owned by Bosch. They supply Worcester boilers dirt cheap.

How Does a Heating Pump Work?

The pump in a central heating system takes hot water from the boiler and pumps it around the pipework in your property. This feeds the radiators, taps, towel rails and showers in your property. If a central heating pump is not working, it can wreak havoc on your whole heating system.

Where is the Pump Located?

Central heating pumps are located behind the casing on the boiler.

We’re going to cover the most common heating pump problems and what can be done to fix them (or, how much they cost to fix).

Pump Problem 1: The pump is running, but it’s not pumping water around the system
Pump Problem 2: Pump is Blocked Full of Dirt
Pump Problem 3: Airlocks & Noisy Pumps
Pump Problem 4: Incorrect Installation
Pump Problem 5: Pump Speed Settings are Incorrect
Pump Problem 6: Leaking Pump
Pump Problem 7: No Power
Pump Problem 8: Pump Won’t Turn Off

Pump Problem 1: The pump is running, but it’s not pumping water around the system

If the heating pump is running, then it should be vibrating slightly. The most likely cause of this problem is that the shaft or propeller on the pump is stuck.

On some occasions (especially when the motor is extremely hot), the pump’s motor is the problem. The pump will get warm, but it shouldn’t be hot to the touch.

This is particularly common on heating systems that have been left sitting for a while.

The Fix

If a component on the pump is stuck and the pump is not circulating, sometimes a gentle tap will free up any seized components.

If the seizure is happening on a regular basis, it’s a good sign the heating pump is on its way out and is likely to fail altogether.

A replacement pump is likely to cost £200-250 including installation. This is for a top brand pump such as Grundfos. You can get exact prices here.

Pump Problem 2: Pump is Blocked Full of Dirt

As central heating systems age, dirt and metal particles from radiators and pipework break down and begin to flow through major components such as the heating pump. This dirt and grime builds up in major components in the boiler and causes them to fail. Luckily, pump blockages are quite easy to fix, as all it requires is a little bit of cleaning.

It’s common for the boiler pump to build up with dirt and then stop working correctly. When this happens, you’ll find your heating system heats up slowly, not to full temperature, or not at all.

The Fix

The first point of call would be to hot flush the heating system with chemicals. This differs to a power flush as it doesn’t increase the pressure in the system. Increasing the pressure on old systems can weaken joints and components and cause leaks.

Once the system has been flushed and the pump has been clean, a good preventative measure is to fit a magnetic system filter.

The magnetic system filter will catch a lot of the debris and help to prevent any future heating pump problems.

Always ask an engineer to check the heating pump when they come to do an annual boiler service.

Pump Problem 3: Airlocks & Noisy Pumps

Another common heating pump problem is air locks. If air builds up in the pump, the pump will stop working correctly.

Many heating pumps have a bleed screw that can be used to remove the air, and allow the pump to work again without replacing any internal parts.

If you hear noises coming from the pump that don’t seem normal, airlocks are likely to be the problem. A lot of customers complain of a constant humming noise when airlocks are the problem.

The Fix

Once the pump has been located on the boiler, look out for a small bleed screw. Please bear in mind that the pump is full of water. Open the screw extremely slowly (less than a quarter of a turn will usually be enough) as there is likely to be a small amount of water leaking out of the pump once all the air is bled.

If this doesn’t fix the problem, it’s likely the pump noises have always been there. Some manufacturers supply anti vibration brackets which are easy to install.

Pump Problem 4: Incorrect Installation

Not all heating pump problems can be blamed on the pump. If the system has never worked correctly, there’s a small chance that the pump may have been installed incorrectly. In a worst-case scenario, the pump has been fitted the wrong way.

The Fix

This is extremely uncommon, but if the pump has been fitted incorrectly, then it needs to be switched around. Remember, the system must be drained down before the pump can be removed and then turned.

After refitting the pump, the system will need to be filled using the filling loop on the boiler. And remember, all radiators and towel rails will need to be bled.

Pump Problem 5: Pump Speed Settings are Incorrect

Newer pumps (such as the Grundfos 15/60) will have speed and flow settings. They are extremely easy to adjust.

And usually they are between 1 and 3. 1 is the slowest flow rate and 3 is the highest. On many properties, we have been to that have had radiators not getting hot, or the whole system not getting to temperature, the pump flow rate is the issue.

The Fix

Locate the boiler pump. On top of the pump will be a switch. If this switch is set to 1 or 2, there’s a good chance that the flow rate is too low. The pump can be flicked to 3 which is the most powerful setting.

It’s worth consulting a Gas Safe engineer first. The pump may be set at 1 or 2 for a reason (such as a system doesn’t allow any further flow due to microbore pipes). Turning the setting up on a system that doesn’t require it could result in leaks or broken components in the boiler.

Pump Problem 6: Leaking Pump

Boilers leak for a whole host of different reasons. One of the most common reasons that a boiler leaks is issues with the pump. This can be down to incorrect installation, the pump working itself loose, or even a blown seal due to incorrect pressure settings.

The Fix

Check that the pump is secure. If it’s not, tightening it up can sometimes be enough to stop a leak.

Check all the fittings on the pump. Corrosion maybe the cause of the leak. If this is the case a new pump will need to be fitted.

Finally, check the joint on the pump. If this is what is leaking, there’s a good chance that it’s the seal on the pump that is blown.

The two options here are to replace the seal, or replace the pump. If the pump is particularly old, a replacement is the best option. You can get prices for a replacement here.

Pump Problem 7: No Power

If the pump and boiler have no power, but your property has power, the likely cause is going to be the PCB unit. Hopefully, your boiler has power. If it’s just the pump that has no power (or won’t start up) there’s likely a wiring issue. On some occasions, small leaks can ruin the wiring on the pump.

The Fix

First, start with the easy and obvious. Like other appliances pumps have fuses. Check that the fuse isn’t blown.

Also, check that are no leaks. If there isn’t, have a Gas Safe engineer come and check the wiring to the pump.

If the pump is old and corroded, there’s a good chance that other parts are going to fail and a replacement is likely in order.

Pump Problem 8: Pump Won’t Turn Off

Most pump problems are related to pumps not working. However, on rare occasions we are called out to boilers where the pump constantly runs and won’t switch off. We’ve seen this to be a problem with the Baxi Solo range on a number of occasions.

The Fix

A proper pump diagnostic needs to take place. In the past, we’ve seen pumps constantly running due to:

  1. Faulty PCBs (the circuit board on the boiler).
  2. Pump overrun stat is faulty.
  3. The mid position valve is sticking (this can be lubricated with WD40).

What’s Next?

If you have any questions relating to heating pump problems, please leave a comment below and we’ll get back to you. And we have another article covering heating and boiler problems here.

And, if you want a quote for boiler pump repair, click here. Prefer a new boiler with a long warranty? Get your price online using this clickable form.

33 thoughts on “The 8 Most Common Central Heating Pump Problems [And Fixes]”

  1. Could you please advise me on correcting a problem on why the central heating pump continues to run when both heating and hot water have been switched off at the controller.
    Many thanks
    Howard Evans

    • If it’s just for a minute or two, don’t worry. It’s pumping excessively hot water from your boiler so it doesn’t cause any damage.

      It needs a diagnostic, but a good start is checking the pump is communicating properly with the PCB via the heat sensor.

  2. I have a firebird super q 50/82.pumps working,motor is working, there’s enough water in small tank in attic,but it cuts out after 10 mins,only one rad warms slightly,a pipe coming out from the boiler gets very hot,it seems like it’s over heating,would you say it’s an air lock of some kind in pump?or is there a thermostat that could be gone? any suggestions of what it might be,will I need a pro to look at it?

  3. Hi Martina,
    Could be a tonne of things. But, sounds potentially like sludge in the system, air locks or bad piping (microbore when it shouldn’t be for instance).

    Starting with air locks, you can bleed the rads with a drain key. If that doesn’t work, I’d look at getting an engineer out.


  4. Hi
    I want to change my central heating pump but not sure which on to get. I have 15 radiators in my house, so would a standard one be ok?
    Many thanks Andy

  5. Hi. I have recently had two new radiators downstairs the central heating was all working fine but recently one of the radiators doesn’t work when the system is cold to get it to warm up I have to turn half the other radiators off in the house and after a short time you can hear the radiator bubble then it will warm up after turning all the radiators back on I bleed them all and a little air does come out. I have been doing this for 3 weeks now is there something that is causing the air to get in to the system? I have a condensing boiler many thanks

  6. Hi
    I have a radiator problem….the radiator in living room is a double panel radiator but its not hot compared to other single panel radiators…. there is two pipes coming to the radiator in which one pipe is cold….can anyone tell what will be issue….

  7. Hi, I have an Ideal Logic heat 24 boiler. Noticed the thermostat wasn’t turning the boiler off, so naturally turned the programmer to off. Didn’t stop the boiler, but turning down the min max on the boiler did. Noticed however that the pump continues to run, seems the only way to stop the pump is to cut the power to the boiler. Any idea if there’s a fix I can attempt or is it engineer time?

    Cheers, Jonathan

  8. Hi. We have just installed a new Grundfos pump and it makes a loud humming noise that vibrates through the pipes. We have checked the installation and bleed it but it makes no difference. Is there anything else we can try? Thanks.

    • Hi Cheryl,

      There’s a lot of things it could be, so I’d get a boiler repair specialist in, or contact Grundfos.

      Pump could be too large/too high a speed setting. It could be too small, so water is overheating.

      By “checked the installation”, what do you mean? Are you sure the pump’s shaft is horizontal?

      They have 2 technical contact numbers:
      01525 850000
      01942 263628

      Hope that helps

  9. Hi, my radiators heat up when boiler is on. Once it does, the boiler switches off and radiators go from too warm to completely cold as if everything is switched off until boiler switches on again. This cycle continues all day.
    Shouldn’t the radiators be constantly warm with continuous circulation even when boiler is off? Is the problem with pump? Please advice so that I know what I’m talking about when I call the BG engineer.

    • Hi Bharath,

      Assuming you have no cold spots on your radiators once they’re heated, and they heat/cool down in tandem, I’d lean towards a thermostat issue. It’s quite hard to diagnose without seeing the property, but that’s usually the case.

  10. Hi, Since we had a new Grundfos Alpha2 pump installed the boiler has been cutting out. We’ll be without heat and water for hours then it will kick in for 10 minutes and then switch of again. Or the heating will be on and on irrespective of the temperature on the thermostat. Since the new pump we replaced the valve, thermostat and the timer and the boiler still cuts out.
    Do you think this is an issue with the pump?

    Many thanks


    • Hi Bulent,

      There could be a tonne of issues, but as you’ve just had a new pump fitted, I’d speak to Grundfos first:
      01525 850000
      01942 263628

  11. hi
    our heating does not warm the radiators when boiler is on’ but the hot water get hot ,i have looked at the pump it does seem to be working but when i try to change the speed it makes no difference the pump seems to work on the same speed what ever setting i put it on
    i can feel it vibrating so it is doing something but not what it should do
    any ideas

  12. Hi. My radiators are hot upstairs but cold downstairs. I have loft tank, hot water tank with pump on 1st floor and boiler downstairs. 7 rads upstairs with 6 rads downstairs.

    This seems to be common problem and lots of threads online. Based on those i think I’ve done the obvious things….

    1. Check pump – seems to be running if a bit hot. Released the air in the pump and checked it’s not seized.
    2. Checked the water tank upstairs. Water seems to be filling when the valve is open.
    3. Tried to balance the rads. No luck. When all rads upstairs are turned off, i can get heat to most of the rads downstairs. But as soon as I make a quarter turn on any rads upstairs I lose all heat downstairs.
    4. Motorized valve is operating.
    5. Not running any zones and one thermostat downstairs is operating.

    Not sure what to try next other than call someone out.

    Any advice would be gratefully recieved.

  13. Hello, we’re finding that our downstairs radiators are only working with the upstairs ones switched off. The radiators also don’t seem to be cooling down when the control panel is set to off. We’ve also recently noticed a drop in hot water pressure, if the turn the shower and bath tap on and off again, pressure comes back but only for a short time. Could these be signs that our pump needs to be replaced?

    Thank you!

  14. Our “Potterton heatmax combi” boiler is dripping clean water from the bottom left. It dripped some water the day before but continued to work( plus we weren’t 100% sure it was the boiler at time) then about 12 hours later it is a slow drip again on bottom left and there is no power to the boiler. Turned it off at the wall and unsure what is wrong( costly?!)

  15. I have Grunfoss Pump that all of a sudden is making a noise….but one day it is ok then the next it’s noisy again, it may go 2 days and not make a sound then it starts again. The ch and hw work fine and boiler seems fine too. Why is it noisy only intermittently????? it’s 4 years old. What is wrong with it…bleed it via silver screw and it dribbled water, no hiss of air.


  17. About 3 months ago I got a new Grundfos water pump for my central heating system. I have a Baxi Solo boiler, and the water tank and pump are in the airing cupboard in the spare bedroom.

    When the heating comes on in the morning, the pump has started to make a loud noise, it’s quite high pitched, and the boiler also seems to be quite loud (making a humming sound). Both seem to be loud at the same time.

    However, the noise isn’t permanent, it comes and goes. The pump will be noisy for maybe 20-25 minutes, then it goes back to normal again, then it will start again after a while.

    Before I got the new pump, the system was drained as I had a problem with a downstairs radiator. Once the problem was fixed, all radiators were bled except two in the living room as the valves are broken and those radiators cannot be bled.

    Could my problem be an airlock in the system?

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