Central heating problems are often due, not to the boiler itself, but to peripheral components such as central heating pumps and motorised diverter valves.

These parts are among the few moving components in the system and so are more likely to be subject to wear and failure over time.

But how do you know that it’s actually the central heating pump that has failed? What are the most common central heating pump problems? And, what are the key differences between a central heating system failure and a central heating pump failure?

In this guide we’re going to run you through some general tests you can do, as well as some central heating pump queries, as well as help you identify if it’s the central heating pump that is causing the problem, and then hopefully provide you with a solution to the issue.

This guide will cover the following:

Basic central heating pump checks

Before you panic, call a plumber and buy a brand new central heating pump, we advise performing a few basic checks. More often than not, central heating pump issues are down to a tripped wire. So, if your pump isn’t working, check the below.

- Check that the power to the pump is turned on

- Check that the power supplying the pump has not tripped out

- Try resetting the pump by switching off the power for a few seconds

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How to test a central heating pump

First, you have to ask, where is the central heating pump?

It is usually found in one of the following locations:

  • Near the boiler
  • Near the hot water cylinder in non-combi systems
  • The rear of an airing cupboard
  • Under floorboards (in older houses)

How to test if a central heating pump is working

If you think you central heating system has failed and needs to be tested, follow the following steps:

Step 1. Find the pump

Step 2. Inspect the pump for any visible damage

Step 3. Turn off the power supply

Step 4. Loosen the silver plate by half a turn, found in the centre of the pump

Step 5. Remove the silver plate, if the water is cool enough

Step 6. Check if the pump shaft has seized

Step 7. Turn the power back on

Step 8. Bleed the system 

Step 9. Check for a broken impeller

If you do all of these steps and the problem isn’t fixed, you should contact a professional.

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How to bleed a central heating pump

You may need to bleed a central heating pump when the air trapped inside the pump stops running correctly. This can damage some of the pump's components and can cause the pump to burn out.

How do I know if my central heating pump needs bleeding?

You can identify if a central heating pump needs bleeding by one of the following problems:

  • Your pump is making a loud knocking sound
  • Your pump is not adding pressure to the central heating system
  • Your pump is hot

When you’ve identified the problem, it’s time to bleed the system. You will need the following tools:

  • Towels
  • Pliers
  • Bleed key / flat head screwdriver

Once you’ve got the tools ready, follow these steps to bleed the radiator:

Step 1. Turn off the power

Step 2. Protect against water damage

Step 3. Turn off the water at the shut-off valve

Step 4. Slowly remove the pump bleed screw

Step 5. Mop up the water that comes out of the pump

Step 6. Screw the bleed screw back into place

Step 7. Turn the power back on

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What speed should a central heating pump be set to?

Every central heating system is different, and will need a different speed setting. If your home has 10 radiators, or 30, 20 metres of piping, or 100 metres. These elements impact how quickly and easily water can circulate your home. 

This is why central heating pump manufacturers developed a variable speed dial that allows you to increase or decrease the speed water circulates around your home, depending on what your home needs.

What happens if it’s set at the wrong speed?

If it’s set too fast:

  • It will waste electricity and cause your bills to rise
  • The pump will make lots of noise
  • The water can return to the boiler too warm and damage the pump

If it’s set too slow:

  • Water cools before reaching the radiator
  • The boiler can overheat

How to find the best speed setting for your central heating pump

Option 1 is to set the pump to the lowest speed and slowly increase the speed over time, but this can take too long and can be inaccurate.

Option 2 includes the following steps:

Step 1. Open all radiator valves

Step 2. Set the thermostat to maximum

Step 3. Set the speed to maximum

Step 4. Wait 10 minutes

Step 5. Turn the speed to minimum

Step 6. Wait for 20 minutes

Step 7. Check if the radiators are still hot, if yes, leave the setting. If no, set to medium

Step 8. Wait for 15 minutes

Step 9. Check if the radiators are cool, if so, set pump to fastest speed setting

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How to recharge an expansion vessel

Expansion vessels are essential for closed-water systems like combi boilers. They’re a crucial part of your heating system that allows it to maintain a constant pressure. If you have a closed-water heating system in your home, such as a combi boiler, you will have an expansion vessel.

Over time, the expansion vessel can become depleted, which can lead to decreased water pressure. If you notice your water pressure declining, it may be time to recharge your expansion vessel.

Recharging an expansion vessel is to remove excess liquid and replace what was removed.

How does an expansion vessel work?

It helps to ensure the boiler can operate safely and efficiently by providing a space for the expansion of water as it is heated. Without an expansion vessel, the pressure in the boiler could become too high and cause the boiler to malfunction or even explode.

How to locate the expansion vessel

The expansion vessel is usually located near the boiler, sometimes even inside the boiler casing. If you're not sure where it is, or can’t find it, you should ask a qualified heating engineer for help.

How to charge an expansion vessel

1. Inspecting the system

Make sure all the fittings on your boiler are tight and that there are no leaks.

2. Draining the tank

Turn off your boiler’s switch and close the pipe valve that connects from your water tank to the expansion tank. Open the valve of your water tank and remove the six sided container. Drain the tank completely

3. Recharge the expansion tank

Make sure there is no water left in the expansion tank before removing any valves or hoses. Once the water is drained, reattach every connection and seal tightly. Turn on the water valve and listen for running water sounds, when the water has stopped flowing, check the air pressure, it should be between 10 and 12 PSI.

And that should be it! If you have any trouble, contact a professional.

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How to stop water hammer

Water hammer is when you can hear banging in the pipes when a tap is turned off. It’s a shockwave that results in pipes moving and hitting each other or the frames they’re in. Water hammer isn’t just an annoying noise, it can result in permanent damage to your pipes. So when you hear it, it needs to be fixed straight away.

What causes water hammer?

The most common causes of water hammer are:

  • Loose pipes
  • New kitchen appliances
  • Worn stop valves
  • Clogged air chambers
  • Water ripples from the tank
  • Fast-acting valves

How to fix water hammer

Water hammer isn’t just irritating - it can also go on to damage different components of your plumbing and pumping systems. That’s why it’s important to get rid of water hammer as soon as possible. A loose pipe or worn stop value could end up costing you thousands of pounds.

The best fixes for water hammer are:

  • Secure any loose pipes
  • Wrap pipes in foam insulation
  • Fix washing machines or dishwashers
  • Install a water-pressure regulator
  • Install an air chamber
  • Install mechanical water shock arrestors
  • Install a Grundfos UPS circulator pump

If you’re not sure which method is right for you, we recommend contacting a professional so you know to make the most informed decision.My Central Heating Pump is not heating the Radiators 

My central heating pump is running, but it’s not pumping water around the system

One of the most complained about central heating pump problems is: how the pump is running, but it’s not actually pumping water around the system. This is a complicated matter that could be caused by several issues. The most likely is that the propeller on the pump is stuck. This could be due to debris blocking the propeller, or it could be that one of the propellers is actually damaged.

Solution:

If debris is blocking the propeller then you will need to get your hands dirty and actually work on removing the blockage. If the propeller is damaged then you will unfortunately need to purchase a new pump.

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My central heating pump is blocked full of dirt and debris

Another complaint we often hear is how the pump is full of dirt and debris. This is due to the ageing central heating system. As the pipes and radiators get older they can start to break down and rust. This can build up within the pump and eventually inhibit the pump’s ability to move water efficiently.

Solution:

Again, if debris is impacting on the performance of the central heating pump then you will need to get your hands dirty and actually work on removing the blockage. You could also contact a plumber to conduct a chemical or power flush on the system. This would certainly clear the blockage, but please keep in mind that the latter could weaken joints and components.  

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My central heating pump is noisy

A central heating pump in full working order will have a slight hum and a minor vibration. If your pump is making excessive noise then it’s a clear sign that something is not working correctly.

The most common reason for excess pump noise is airlocks. This is where air gets into the pump and stops the water flowing smoothly.

Solution:


Most central heating pumps, especially those supplied by quality pump manufacturers like Grundfos, will come fitted with a bleed screw.

This is a small component that can be used to remove air from the system. It is our firm advice that you follow the manufacturer's instructions when carrying out this task.

If your Grundfos pump is not working or you cannot find the bleed screw, contact the manufacturer for help.

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My central heating pump is leaking

It’s a pretty obvious one, but if your pump is leaking then you have a serious problem. Leaking could be due to incorrect installation, the pump over vibrating (causing bolts to break loose), or it could even be that the pump has blown a seal to overpressure.

Solution:

If the pump has come loose then tightening all the bolts should fix the issue. If the leak is a more severe issue and is caused by something like a blown seal, then you will probably need to contact your pump provider. Most pumps will come with either a 2 or 5 year warranty.

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My central heating pump has no power

One of the more severe central heating pump complaints is a pump with no power. If the rest of the system (and your home) has power, then this is likely down to damaged or loose wires. Occasionally, on cheaper pumps, small leaks occur as the pump ages. If the leak gets to the wiring of the central heating pump then the pump will shut down.  

Solution:

Unfortunately, even if you manage to fix the damaged wires, it is unlikely that you will be able to fix the small leaks in the system. This means that you will have a continuous battle trying to keep the pump alive. Try contacting your pump provider in the first instance, as most pumps will be sold with a 2 or 5 year warranty (depending on the manufacturer).

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My central heating pump is not adding pressure to my central heating system

If the central heating pump stops adding pressure to your central heating system then it’s a good sign that something is wrong. Make these checks below:

Airlocks

As mentioned above, airlocks will stop water from flowing around your system smoothly. This will inhibit the performance of your pump and it could also become quite noisy. To fix this issue you will need to bleed the air out of the system. Please carefully read the manufacturer’s instructions before performing this task.

Frozen Pipes

If the weather has suddenly turned and the temperature drops a few degrees below zero, then there is a chance your pipes could be frozen. This often happens when the system doesn’t get used when people are away over the Christmas period. Remember, stopping pipes from freezing is easier than thawing out pipes. If the pipes are frozen then you will need to get space heaters, oil heaters and hair-dryers to thaw out the system.

Solution:

If you have tried both of the solutions above then it is probably time to call a plumber. In higher end pumps, the pump can actually detect when there is something wrong with the system and shut itself down. Again, it could also be due to smaller leaks occurring inside the pump. If you need to replace the system, check with the pump provider as you could be entitled to a free replacement under a 2 or 5 year warranty.

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My central heating pump is too hot

The majority of central heating pumps will be warm to the touch. They are, after all, highly engineered tools shifting vast amounts of water at high speed. But, if the pump is getting hot to the point that it is difficult to touch, then it is clear that something is wrong.

Solution:

Unfortunately, if the pump is too hot to handle, then it is a sign of ageing and you will probably need to replace the pump. If the pump was bought within the last few years then you will probably be able to get a replacement from the pump provider under a warranty. Here at Anchor Pumps we offer 2, 3 or 5 year warranty depending on the pump manufacturer.

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My central heating pump is not heating the radiators

If the hot water pump is not working properly and only pumping enough water to reach some of the radiators in the system, then it’s likely that your pump pressure setting is set too low. There is also a chance that it could be debris in the system that is slowing down the flow of the water.

Solution:

First, try adjusting the pump pressure dial. This is a small dial fitted on most high quality pumps that will allow you to adjust the pressure in your system. Remember to add pressure to the system slowly. A sudden jolt could damage or weaken joints in your system.

If this doesn’t improve flow in the system then you may need to contact a plumber to flush the system. This should help remove and break up debris.

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My central heating pump is constantly turning itself on and off

A strange complaint we occasionally hear is how the pump is constantly turning itself on and off, or the central heating pump is not switching off. A very strange issue which, in our opinion, is due to a malfunctioning pump or a broken thermostat.

Solution:

The first check is to ensure the thermostat is operating correctly. Occasionally a dial can break, causing the pump to constantly start up and then shut itself down.

If you have checked the thermostat and it is in full working order, then it’s likely that the pump is malfunctioning. If your central heating pump is not working properly, contact your pump provider, as you will likely be owed a free replacement under warranty.

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My central heating pump is not making any noise

If your central heating pump is not making any noise and appears to be dead, then you may have an electrical issue. This could be due to a tripped RCD, a blown fuse or even a loose wire.

Solution:

Firstly, check that the RCD has not tripped. The RCD is usually located near the electricity meter or hidden away in an airing cupboard. If the RCD seems to be in full working order then you will need to check that the pump has not blown a fuse.

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So there you have it, hopefully after reading this guide on all things central heating pumps, you’ve managed to solve your heating problems. If for any reason you couldn’t find the information you needed, contact a professional heating engineer, or for free advice, use the contact details below.

Free Advice

If you’re struggling for advice, ring our dedicated pump experts for free advice on: 0800 112 3134 or 0333 577 3134.
We’re open Monday to Friday 07:00 - 17:30 and Saturday 08:30 - 12:30.