Why Your Boiler Is Making Noise And How To Fix It

If you have a noisy boiler and are desperate to fix it, this is the guide for you. There are all sorts of things that can cause a boiler to make noise. In this guide, we will tell you all the likely causes and identify some of the key fixes that can keep things quiet.

A noisy boiler is one of the most annoying things. That endless tapping or whistling that forces you to make a choice between being warm or being able to hear the TV. It is enough to drive anyone to distraction.

Fortunately, we are here to help with a short guide that should help almost everyone to get to the bottom of what is making all that noise.

No matter what type of boiler you have and what sort of noise it is making, we will do our best to provide you with a solution.

What sorts of noise is your boiler making?

Boilers can make a surprisingly wide variety of different noises including:

  • Whistling
  • Vibrating
  • Humming
  • Banging
  • Tapping
  • Clicking

These different noises can sometimes be an indication of the type of issue they have, but this isn’t always the case. This is why we have to dig a little deeper than just the type of noise your boiler is making if we want to identify the problem.

The 7 Most Common Reasons Your Boiler Is Making Noise

The truth is that there are a lot of reasons why a boiler could be making noise and if we tried to deal with them all in this guide we would be here all week.

But there are some issues that are far more common than others and in this guide, we are going to highlight the 7 most common reasons for boiler noise, explain what is causing them, and then also show you how to fix them.

#1 – Sludge Build-Up

The issue of sludge build-ups can occur in any boiler and any central heating system. It is common for small bits of the radiators and pipework to come away and over time this builds up into a sludge that can build-up anywhere in your system.

If it happens to gather in the wrong place, this can result in various tapping or clicking noises. This is usually caused by particles of metal repeatedly hitting the side of pipes, radiators, or boiler components.

How to Fix it:

Getting rid of a sludge build-up is fairly simple. The first way is to put an inhibitor and cleaner into your system, to break down any sludge build-up. This can be done yourself but a lot of people are more comfortable getting an engineer in.

Another option is a hot flush which your engineer will need to do. This involves pushing various chemicals around your system to clear out any sludge build-ups. Some engineers may offer a power flush, but these should only be carried out on newer systems as they can damage old pipework and boilers.

Once the issue has been fixed, it is worth ensuring your boiler us fitting with a filter to catch heating sludge as it goes around and stop it building up. Make sure you get this cleaned annually as part of your boiler service.

#2 – Limescale Build Up

Limescale is another thing that can build-up in your pipes or on components in your boiler. Limescale is far more common in hard-water areas.

It leads to steam bubbles being created in your system and when these pop they are likely to cause various noises including tapping and banging.

How to Fix it:

Limescale is difficult to remove. The best way is to put a central heating inhibitor into your system and then flush the system.

This will usually remove most build-ups but it is not guaranteed to be 100% successful. If the build-up is on boiler components and has gathered over many years, your best bet might well be to invest in a new, modern, energy-efficient boiler.

Once the issue has been resolved, be sure to get your engineer to install a limescale reducer. This should help you to catch any limescale floating through your system and help to prevent future build-ups.

#3 – Airlock In The Central Heating Pump

The central heating pump is a crucial component within your boiler that pushes hot water around your central heating system.

It is fairly common for airlocks to build up in the central heating pump and this will cause banging which will usually be heard either when running hot water or shortly after your boiler is turned on.

How to Fix it:

Almost all modern boilers contain a central heating pump that is fitted with a bleed screw. This works a little bit like a bleed key on a radiator and allows you to release any air that has built up.

Just turn the bleed screw about a quarter of a turn. You should hear a hissing sound as the air escapes. When a trickle of water appears, that means all the air is out and you can now close the bleed screw.

Once you have done this, the banging noise should stop.

#4 – Ignition Failure

If your boiler is making a clicking or light tapping noise but then failing to fire up, it is likely that there is an ignition fault.

The noise that you can hear is the boiler trying and failing to ignite.

How to Fix it:

This is a problem that you will definitely to call out a qualified gas engineer to deal with. The cause could be due to an issue with your gas supply or a fault with your boiler’s ignition.

It could also be something more serious that is causing your boiler to prevent itself from igniting. Whatever the reason, you will need professional help to resolve this one.

#5 – Heat Exchanger Blocked Or Faulty

If there is a problem with your boiler’s heat exchanger, this will usually result in a whistling or gurgling noise a little bit like a kettle boiling.

This is not a good thing as it suggests that either the component itself has a problem or there is a build-up of limescale that is causing the issue.

How to Fix it:

Limescale build-up in the heat exchanger could be a major issue. It is quite likely to cause the component to crack if it isn’t dealt with quickly.

A hot flush as we discussed in issue #2 in this guide is the first course of action. If this doesn’t resolve the problem, you will need to get your heating engineer to take a closer look. It might be the case that you need to replace the entire component.

If that is the recommendation, take some time to think about the best course of action. Heat exchangers are expensive to replace and you could end up spending more than £500 to get the issue fixed.

If you have an older boiler that is out of warranty, you would probably be better off buying a whole new energy-efficient boiler instead. You can find out more about how to do this at the bottom of this guide.

#6– Low Water Pressure And Flow Rate

If your boiler is experiencing low pressure, it can sometimes lead to a loud water-hammering noise.

This is often caused by fluctuating water pressure which slows down the water flow and then suddenly increases to push the water through your system extremely fast.

Often, this noise can be quite alarming and people regularly assume that this means it is a major problem. Fortunately, this is not usually the case.

How to Fix it:

A loss of pressure in your boiler usually means there is a leak somewhere in your central heating system. You can top up the pressure in your system manually to see if this fixes the problem but if the pressure goes down again it is almost certainly caused by a leak.

If there is a leak, you can check the pipework, joints, and radiators for evidence of a leak and if you locate the problem, fix it. This should resolve the noise issue.

If there is no evidence of a leak, it is likely that your boiler is set to the wrong flow rating. Most boilers will have a flow rate setting on top of the central heating pump. This is visible if the front casing of the boiler is removed and if you increase the setting it will often fix the issue.

But a word of caution, increasing the pressure of your boiler can be risky so be sure to check your manual to ensure you don’t increase it too much and if you are in any doubt at all, consult with a qualified engineer.

#7 – Seized Up Pump Components

There are various moving parts inside your boiler and if these seize up it is likely to cause a noise as well as stop your boiler working properly.

The noise you are most likely to hear as a result of a seized up component is either a humming or a regular vibrating sound.

The majority of times, a seized up component is likely to be linked to the central heating pump. Be aware that pumps do make a slight humming noise even when working properly, so be sure the noise is more than normal before you start to think about fixing it.

Place your hand on this component. If it feels hot (more than warm) it is likely that this is the problem.

How to Fix it:

A quick and easy fix for a seized up central heating pump is to tap the component gently. This will often free up the issue and get things working again. But this is often only a temporary fix and the issue may well reoccur.

If it does, a possible cause could be a limescale build up (see problem #2) or a sludge build-up (see problem #1). You will usually need to get a qualified engineer out to solve this problem.

#8 – Noisy Pipes

Even if it sounds like the noise is coming from your boiler, often the real reason can be an issue with your pipes. The most common cause of noise in pipes is a blockage.

How to Fix it:

Blockages in pipes are almost always caused by a build-up of either sludge or limescale, so once again you can refer back to problems #1 and #2 to identify the best solutions.

Where to buy a new boiler?

If your boiler is fairly old, out of warranty, and you are being quoted a big fee to fix or replace a major component, you are probably going to be best to replace it with a whole new boiler.

If that is your decision, we strongly recommend that you get a quote from WarmZilla.

WarmZilla is an online boiler installation that offers rock-bottom quotes on a huge range of high-quality boilers. They stock all the major manufacturers and frequently have special offers and exclusive deals available.

It is always advisable to get multiple quotes before buying a new boiler, but we strongly recommend that you make sure WarmZilla is on your list.


Noisy boilers are extremely irritating and most people want to get them fixed as quickly as possible.

We have put this guide together to help by identifying the most common causes of boiler noise and explaining how to fix them.

We can’t guarantee your issue will be covered here but we are confident that the majority will be.

If you have any questions that we haven’t dealt with in this guide or any advice for our readers that we have missed out, please do share it with us using the comment box below.

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