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Last updated: 17th October, 2022


How Do You Fix a Boiler Kettling Noise?

How Do You Fix a Boiler Kettling Noise?

Is your boiler making some strange noises? Chances are its 'boiler kettling' and here is how you fix it.

If you have ever noticed strange noises coming from your boiler, or that your boiler is making incredibly loud and horrible sounds, then you might have just experienced boiler kettling.

It can be a problem that any system runs into eventually, but understanding how it happens - and how to fix it - can be important for keeping your boiler noise low and your home quiet.

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What is Boiler Kettling?

There isn't a single boiler kettling noise: the term 'boiler kettling' basically refers to any noises your boiler is making that aren't normally supposed to happen.

This could be banging noises, high-pitched hums, or anything that sounds like a symptom of some dangerous problem.

The word "kettling" comes from the fact that a kettling boiler often sounds like, well, a whining kettle.

No matter what sound they are making, it can cause your boilers, pipes, and other parts of your heating system to become much louder and less comfortable to live around.

Is Boiler Kettling Dangerous?

A kettling boiler is not necessarily a sign of a damaged central heating system, and your boiler won't suddenly spray searing hot water onto you.

Often, a kettling boiler is suffering from a smaller issue that has not been taken care of properly, which can happen if you do not regularly check your boiler for common problems.

Why is My Boiler Kettling?

There are a few major common causes of boiler kettling, although some of them are more common in particular system designs than others. These include:

Leaks That Create Boiler Noise

If your pipes or boiler has a leak, then your boiler will start to kettle as it tries to manage the water flow and pressure properly.

Even a small leak can alter the pressure in certain pipes, leading to noisy whines that may only occur when you are actually boiling water.

These leaks can spring up for a range of reasons, from badly maintained pipes to corrosion and poor boiler pressure management, but it is easy enough to repair if you can afford the cost of some new pipes.

Serious leaks might require a greater cost to fill and repair, but they can also cause much more serious damage if they are allowed to linger for too long.

In major cases, it may be best to just get a new boiler, especially if your current one is old and has begun to break down on a regular basis.

Even an older boiler is very unlikely to wear down to the point that it actually explodes, but having an old and damaged container full of hot water can be very dangerous either way.

A Build-Up Of Limescale

Another one of the common causes is a limescale build-up, which can happen in any boiler through completely natural means.

The more you use a boiler, the more limescale can build up and start to trap water, mainly around the heat exchanger section.

Once you start blocking the heat exchanger, the remaining water and heat only have so much space to move, so you will usually end up with a boiler making kettling sounds despite being relatively safe to use.

Limescale can also have the side-effect of blocking certain parts of the central heating system with sludge, meaning that you might struggle to get the best performance out of other appliances too.

Getting a new boiler will solve the boiler kettling problem, but you might need to clean out certain pipes near radiators or other areas that could have been affected by limescale build-up and sludge.

The build-up of limescale is much more likely in "hard water". Hard water is any kind of water containing more minerals: your system may have a way to remove some of these minerals and "soften" hard water, but you still need to keep an eye out for the build-up of limescale in the pipes.

If you need to get an entirely new boiler, take the time to clean out the rest of the system too, just in case. Any sludge in the pipes or radiators should also be removed.

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Overheating (Including the Heat Exchanger)

If your boiler is often overheating, boiler kettling is a very likely side-effect. Things like a broken thermostat or fiddly controls can easily lead to overheating, and the problem could go unnoticed for quite a while.

A faulty thermostat might lead to long-term overheating and issues with getting accurate temperatures, even if the flow of water is still fine and performance has not dropped.

When you get a new boiler, check the heating systems and make sure that the thermostat (as well as other controls) work properly.

Overheating can happen for multiple other reasons, and the exact cause will reduce the kettling sound.

Banging could be because something is jammed in an important pipe (like sludge), while whining might be because the boiler is boiling water at an excessive temperature. Of course, every boiler is different, so the kettling noises depend on how the causes impact the system.

How Do I Fix Kettling?

When you have a boiler making boiler kettling sounds, you need to remember that the repair work needed to fix the problem can vary.

Some boilers might only have issues with one water pipe and can take no time to fix, while others might have a major heating issue that requires a brand new heat exchanger system (or a replacement boiler).

A noisy sound also does not always mean a serious issue, so do not assume that a loud noise is a risk to your safety if you do not know the cause.

Flushing The System

For most boilers, a power flush can be enough to clear out sludge, limescale, and any other blockages.

This allows you to force water through the system until you can remove the blockage and stop the sound, which can often be enough to cover some common causes and issues.

It can also be fairly cheap, but it won't fix major heating problems, and you might need some time to carry it out properly.

Preventing Overheating

Resetting the boiler (as well as the thermostat) can help prevent boiler kettling if the cause is excess heat.

You might be able to do this through the manual for your boiler if you still own it, which may save you money that you would otherwise have to spend to get a heating technician out to your home.

Remember that boilers kettle when something is wrong, so check the safety instructions and stop if you are worried about hurting yourself: hot steam can be lethal in some cases.

Patching Up Leaks

If you can identify a leak and get to it, then you may be able to cover up the gap and seal it shut.

Learning to fill in a leak does not take long, and even a temporary fill option or cover can keep your heating stable while you look for a professional.

The best way to approach the problem is by identifying the leak, using a reliable method of sealing it (like professional-grade pipe sealants), and then get somebody with more experience in to double-check.

If the leak is not one that you can identify or reach, you might have to get through the wall, which can cost some money to repair (since you are opening up a wall in your home).

If the leak is extreme and you can't get it sealed properly, then you may have to get that pipe replaced unless you can somehow fill in every individual leak properly. Internal boiler leaks are almost impossible to fill on your own and may require a complete replacement to stop the noise.

Finding Help

In cases where you need outside help (because your boiler is over ten years old, you have lost the manual, the damage is too serious, or for any other reason), you might have to get external help.

Ideally, choosing somebody who is gas safe registered is the best option, since they are authorised and regulated properly by the government.

Companies that are regulated by the Financial Conduct Authority are likely to be gas-safe, so they will be able to handle a complex combi-boiler without the risk of them doing a poor job.

Fixing The Boiler

Make sure that you know as much as possible about the problem since more information can make it much easier for an expert to understand what has gone wrong with your boiler.

If you are not sure of what is happening and can only tell them that the noise exists, they will have to figure out the cause themselves, which can take a lot of time and might even force them to go and get extra tools that they do not keep in their vehicle or toolkit.

If your boiler has totally packed in then maybe it's time for a new boiler. See our guide on best combi boilers which will educate you more on what the best boiler is on your home.

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Stephen Day profile photo
Article by
Stephen Day | Co-founder
Gas Safe registered and FGAS certified engineer with over 20 years experience in the heating and cooling industry.