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9 Common Central Heating Pump Problems and Fixes


Most homeowners dread waking up to a malfunctioning central heating system, especially in the cold winter months. However, before you rush to call a heating engineer, remember the issue might be stemming from a faulty central heating pump, something which you can fix yourself.

Central heating pumps are susceptible to many issues, most of them minor problems that any diligent DIYer can solve. In this guide, we will explore nine of the most common central heating pump problems and their fixes. This way, you get to fix your boiler within a few minutes and save on the expensive cost of calling a heating engineer to handle the job.

 What is a central heating pump, and where is it located?

The central heating pump is simply a hot water pump that takes water from your boiler and circulates it around your property. The pump utilizes the existing pipework in your home to send hot water to your radiators, towel rails, and even the hot water cylinder. And given such a critical role, it can be seen that a slight problem with your central heating pump is enough to bring your central heating system to a standstill.

A central heating pump is usually located behind the boiler casing or next to the hot water cylinder, especially in regular and system boilers. On the other hand, a combi boiler does not need a pump as it supplies water to your taps and showers at the mains pressure.

What are the signs of a faulty central heating pump?

You can easily tell that you have a malfunctioning central heating pump if you notice any of the following tell-tale signs.

  • There is water leaking from the pump
  • The pump casing is hot to touch
  • Unusual noises are coming out of the central heating pump
  • There is no hot water in your hot pipes
  • The water flow pipe is cold, yet the pump is running
  • Some radiators are taking longer to heat up, while others are not heating up at all

Common Central Heating Pump Problems and Their Fixes

  1. The pump is running, but there is no hot water in the system

The central heating pump is the first thing you should check when you find your radiators cold when they shouldn’t. The good thing is, you can quickly tell whether the pump is running or not simply by looking, listening, or touching.

When the central heating pump is running, it tends to vibrate slightly and usually is warm to the touch. So when you locate it, you should touch it to feel any vibrations or warmth that indicates that the pump is up and running.

If the pump is running and there is no hot water circulating in your central heating system, it is most likely that the propeller in the pump is stuck or damaged. On the other hand, if the pump is too hot to touch, the issue is likely to stem from a malfunctioning motor.


If the pump is not circulating water due to a seized component, giving it a gentle tap will free up the stuck element, and your radiators will heat up in no time. However, if this doesn’t work, or the seizure keeps recurring, then it might be time you consider replacing your central heating pump.

On the other hand, if the issue is caused by a damaged motor or propeller, you have no choice but to call a heating engineer. The heating engineer will then assess the extent of the damage and determine whether the pump components are replaceable or you need a pump replacement.

  1. The pump is blocked and full of dirt and debris.

A blocked pump is a common issue in most old central heating systems. With time, dirt and rust from radiators and pipework build up in major central heating system components such as the heating pump. The accumulation of this dirt and grime in the heating pump can inhibit the pump’s ability to move water in the central heating system, and even worse, cause it to stop working.

Luckily, you can detect the presence of dirt and debris in the central heating pump long before it stops functioning altogether. This is usually indicated by your central heating system taking a long time to warm up or not achieving the set temperatures.


If dirt and debris are significantly lowering the performance of your central heating pump, then you have no option but to call in a central heating engineer. This is because an attempt to clear the sludge from the system on your own might result in further damages to your central heating system.

Depending on the level of dirt in your central heating system, the heating engineer might decide on opening the pump and removing the dirt or hot flushing the whole system. A hot flush is preferred to a power flush, especially when dealing with an old central heating system. This is because the high system pressure associated with a power flush can damage joints and components in such systems.

Once the hot flushing chemicals have been cleared from the system, it is recommended that you install a magnetic filter that will trap debris and prevent future blockages.

You can also arrange for your heating engineer to inspect the heating pump whenever they do the annual boiler maintenance. This way, you get to catch the issue of debris accumulation earlier on and prevent future blockages from happening.

  1. Leaking pump

Leaks in a central heating pump can be attributed to many reasons: incorrect product installation, incorrect pressure settings, a blown seal, or the pump working itself loose. Given that leaking can drastically lower the water pressure in your central heating system, you need to move quickly and resolve the issue.


There are several ways to fix central heating pump leak issues, depending on the cause of the leak. If the leak is due to the pump working some bolts loose, you can resolve it by tightening all the bolts and ensuring the pump is secure.

If securing the pump is not enough to stop the leak, check the pump fittings for any signs of corrosion. If there are some corroded parts, you will have no choice but to install a new central heating pump.

Lastly, if a blown seal causes the leaking, you can replace the seal if the pump is relatively new. However, installing a replacement pump would be the most effective solution if the pump is old. A leak caused by a blown seal is easy to point out as the water will be coming out of the pump joint.

  1. Airlocks and noisy central heating pumps

Given that central heating pumps have a motor, it is natural that they make some vibratory noises when in operation. If, however, your heating pump is making strange humming, banging, or clunking noises, then there is a high chance that the pump has an airlock. In addition to the strange and irritating pump noises, an airlock will also reduce the ability of the pump to circulate water in the central heating system.

In a more severe scenario, the unnatural noises coming out of your central heating pump is attributed to broken components or a loose bearing inside the pump. This usually is something you can’t fix yourself, and you will need to replace the pump.


Dealing with pump noises caused by an airlock is relatively easy and requires you to bleed the air out of the central heating pump. Follow the following steps to effectively and efficiently bleed your central heating pump.

  1. Turn off the power to the pump to avoid the risk of an electrical shock during the bleeding.
  2. Lay down towels beneath the pump to protect the floor and electric components from water damage
  • Turn of the mains water supply as well as the water supply to the central heating pump
  1. Using a flatbed screw, slowly remove the pump’s bleed screw and keep it safe (however, do note that even a quarter of a turn is enough to bleed the air out of the pump). You will see a small amount of water leak out of the pump during the operation and trickle into the towels.
  2. Screw back the bleed screw and mop up any water around the pump
  3. Turn the power back on and switch on your central heating system

Usually, bleeding the central heating pump is enough to rid it of unnatural noises. But if the noises persist, the issue might be caused by loose bearings, and you need to replace the central heating pump.

  1. The pump has no power

If there is electricity in your home, but your boiler and central heating pump have no power supply, there is a high chance that your boiler has a faulty PCB unit. And if this is the case, then there is a miscommunication between the central heating and the boiler since the central heating cannot call the pump to turn on.

Alternatively, if your boiler has power but the central heating pump doesn’t, the issue is likely due to a wiring problem. Wiring issues usually stem from blown fuses, tripping, water damage, especially when the pump leaks.


The first thing you need to check for is a blown fuse. If the fuse is blown, replacing it might get the pump to power on.

Next, check the pump for any leaks that might have tampered with the pump’s electrical connections. If there are leaks or any PCB issues, you should consider calling a heating engineer right away. The heating engineer will examine the extent of the damage and inform you whether you need to replace the faulty components or not.

Lastly, if your pump is old, corroded, and approaching the end of its lifespan, replacing the entire pump unit would be a better solution than attempting to resolve the underlying power issues.

  1. Incorrect pump speed settings

Most new pump models are fitted with speed and flow settings that allow you to control the speed and rate of water flowing from the central heating pump. Flow speed options are usually 1, 2, and 3, whereby 1 is the slowest while 3 is the fastest.

If your pump’s flow rate isn’t set up correctly, say, set at 1 instead of 2 or 3, there will be a significant drop in the performance of your central heating system. This drop in performance is usually marked by your central heating system taking too long to heat up or some radiators not heating up at all.


First, you need to locate the flow rate switch on your central heating pump. And once you find it, check the current speed setting, and if it is set at 1 or 2, you need to flick the switch to 3. With 3 being the strongest pump flow rate setting, there is a high chance that your central heating performance issues would go away.

However, it is advisable to consult a certified heating engineer before adjusting pump flow speeds as there is a possibility that the speed setting was set at 1 or 2 for safety reasons. This is especially the case where a new pump is installed in an old central heating system that cannot sustain high pressures.

  1. Incorrect pump installation

Although not a common occurrence, there have been cases where central heating pump issues have been traced to incorrect installation. If a central heating pump is installed the other way round, it is bound to develop plenty of problems, including leaking and unusual noises.


There is only one way of fixing an incorrectly installed pump: uninstalling and switching it around. However, before this can be done, your central heating system will need to be drained first, making it a lengthy and expensive project. And once the pump has been properly installed, you will have to refill the system and bleed the radiators in your home.

  1. The central heating pump won’t turn off.

There are instances whereby a central heating pump decides to go rogue and refuses to shut down. And given that you are used to dealing with issues of pumps that won’t work, seeing yours refuse to power down is enough to send you into a panic. However, there is no need to worry as this is usually an electrical issue stemming from a faulty boiler PCB unit.

It is also worth mentioning that this situation can also be triggered by a faulty pump overrun stat or a stuck mid position valve.


Resolving the issue of a constantly running central heating pump requires a touch of finesse which only heating engineers have. Whenever you experience such an issue, you need to reach out to a certified heating engineer or tradesperson right away.

  1. The pump is worn out.

Have you stopped to consider that your central heating pump might be too old and that it is developing plenty of issues due to it nearing the end of its lifespan? Well, it is good to know that, like all mechanical machines, your central heating pump is subject to wear and tear from being used for long.

If your central heating pump is anywhere between 15 to 30 years old, it is likely approaching the end of its service life. Rather than wasting time and money repairing an old and failing unit, it is about time you consider installing a new pump.


There is no remedy for old age, and you will simply have to install a new central heating pump.

What is the cost of replacing a circulating pump?

If you are afraid your central heating pump is old or can’t be salvaged, you are probably wondering how much it would cost you to install a new pump. There is no definitive answer as the total cost of installation depends on several factors, such as the type and brand of the pump and the ease or difficulty of installing the new unit.

Generally speaking, a pump unit would cost you between £100 to £160, and if you factor in the installation cost, the total costs rise to anywhere between £150 – £350.

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