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Why is my boiler making a noise?

If your boiler is making a strange noise, it could be that it needs to be repaired. If it’s an older model, you may even need to get a new boiler.

In this guide, we'll take a look at each of these noises and what they could mean.

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Normal sounds your boiler should make

Just like most technical appliances, boilers contain moving parts and these are inevitably going to emit a sound. Your heating system is one of the hardest working appliances in your home - heating water and pumping it all around your house is no easy task.

So it’s understandable that you’ll be able to detect some audible sounds such as quiet whirring when the pump is circulating water, deep rumbling when the boiler starts up and occasional quiet clicking when the system is given an instruction by the thermostat.

However, some sounds can be a clue that your boiler needs some attention. Here we look at some of them and the action you need to take.

The boiler is making a banging noise

A banging noise means you could have a build-up of sludge or limescale in your boiler’s heat exchange – causing a restriction of water which begins to overheat and steam.

Known as kettling, this can shorten the lifespan of a boiler and is a common problem in ‘hard water’ areas such as London, Bristol and Southampton for example. These areas have water that possesses high mineral content such as calcium and magnesium, which accumulates as limescale on the boilers heat exchanger.

The easiest way of rectifying the problem of kettling is to have a Gas Safe Engineer carry out a chemical flush. This will clear the build-up of sludge and limescale.

Alternative causes could be a leak in the system caused by corrosion to the pipework or over pressurisation, among other reasons. Again, having an engineer to take a closer look at the leak should be your first port of call if you want to avoid having to invest in a new boiler.

You could also try replacing your thermostat as a faulty one could be causing your system to overheat which can result in a banging sound.

Boiler need some TLC?

Let our experts take care of it with an emergency repair

If you can’t get rid of that annoying boiler noise, you may need to seek help from an engineer.

Our Boiler Plan Gas Safe experts will point out any work that needs to be carried out, they'll also provide a fixed price repair quote.

With our 24 hour emergency repair and 95% first time fix rate, we’ll have your heating up and running again in no time.

Book a Boiler Repair

The boiler is gurgling

The most common reason for a gurgling sound is air trapped in the system or a blockage at the base of your boiler. This trapped air may also be accompanied by cold patches on a radiator. This can be fixed by bleeding your radiators.

You should also check your boiler pressure in case you have low water pressure causing the gurgling noise. Always refer to your user manual, but typically if the reading on the display is below 1 bar, this is a sign of low pressure.

To increase boiler pressure to the correct level, follow our step-by-step guide.

Is a gurgling boiler dangerous?

More often than not, trapped air is an indication that the wastewater (condensate) pipe is frozen, which will need to be thawed to fix. Luckily, this is a straightforward procedure, with the golden rule being NEVER to use boiling water on the pipe as this can cause it to crack.

For a full run-through, check out our guide on how to thaw a condensate pipe.

Another common reason for a gurgling sound is low water pressure. You can check if this is the case by reading your boiler pressure. If it is too low or high, you can fix this easily yourself.

The boiler is whistling

Whistling noises, as well as banging, can also be caused by kettling, a loss of water or even trapped air. It may be that a squeaking or whistling is a sign of a mechanical defect. For example, pumps that need oiling can be prone to making these types of sounds.

Simply bleeding your radiators to release the trapped air could be all that’s needed. While this is easy to do by yourself it may still be useful to call out an engineer, who will be able to identify the root cause and carry out any minor repairs before they become bigger problems.

If you suspect that the whistling noise is coming from a boiler component, getting it check by a professional is definitely the way to go.

The boiler is vibrating

A boiler vibrating noise or a boiler humming noise can be caused by several factors, including a faulty pump shaking inside the boiler casing, as well as a range of other component issues.

If your boiler is making a humming noise, it may also be the case that your pump setting is too high, which results in water being sent around your pipework too quickly, which can result in vibrations, boiler buzzing, trickling and humming noises.

Once again, vibrating sounds can be caused by a build up of sludge inside the boiler. As hot water is passed to the heat exchanger, the sludge stops the flow of water which begins to violently boil, resulting in the noise you hear and the vibration you can feel.

With so many possible reasons relating to boiler humming noises, it’s always advisable to seek the help of an engineer.

The boiler is buzzing and whining

If you can hear your boiler buzzing or making a whining noise, you may have a component issue on your hands. Faulty parts such as a worn pump bearing, a defective burner or vibrating fans can easily lead to boiler buzzing and whining sounds.

As these noises are usually a genuine cause for concern, the causes should be diagnosed and remedied as soon as possible and a boiler repair booked in as soon as possible.

The system is making a bubbling noise

If your radiators are making a bubbling noise, then you may have air bubbles trapped in the system.

Air bubbles are created when you fill your radiators and there is little air left, which is likely why you are hearing a boiler bubbling noise. While these don’t cause any harm directly in the short term, you need to remove them as they can lead to the heating system oxidising which can create sludge build-up.

Bleeding your radiators is the simplest way to remedy the problem of a boiler making a bubbling noise.

Other causes of a noisy boiler 

While the above examples cover most noises, there may be some that are the result of more complex issues and faults. 

To help you work out just what the problem is, your boiler may also be displaying a fault code, which, when referring to your user manual, will refer to the exact issue at hand.

To help you, we’ve listed the codes you should be aware of for each manufacturer.

How to avoid boiler noises

To make sure that your boiler stays in good working order and that it doesn’t develop a suspicious noise, it’s wise to book an annual boiler service of your system.

For complete peace of mind, it’s also a great idea to sign up to a boiler cover plan, which will include an annual service, and, depending on the level of cover, could ensure that you won’t be hit with any nasty repair bills.