Category - Boilers
Guide author photo

Ryan Gill, Engineer

31 Jan : Updated 18 Apr ● 8 min read

9 reasons why your boiler is making a noise

If you've noticed your boiler making noise that varies from how it usually sounds, it's best to act fast to prevent further damage. A noisy boiler isn't always a cause for concern, but there are certain noises to look out for, and each comes with its reasons and remedies.

It's not until our boilers start breaking do we realise the importance of a functioning heating system. So we understand how concerning it can be if you start hearing any of the 9 noises discussed in this guide.

Typically, the problems causing your boiler to make noise can be fixed quickly. But if your boiler is old and ready to be replaced, there’s a chance that the problem might be something a little more severe and, in these instances, it’s important to be aware that it might be time for a new boiler.

In this guide, we’ll take a look at:

1. Loud banging noises

A loud banging noise can come from a faulty boiler thermostat.

This typically means that limescale has built up inside your heat exchanger, causing your hot water to overheat. Either this or your temperature is on the incorrect setting.

You may want to call a heating engineer who can check that your boiler thermostat is set to its correct temperature. If that wasn't the issue, they might need to get under the flooring to check the pipes for any loose screws; another common cause.

A Gas Safe engineer can also determine if the problem is coming from your heat exchanger, which in that case, you may need a central heating powerflush to fix the problem if it is a result of a build up of debris and dirt.

2. Gurgling noises

Typically, a gurgling noise is most commonly caused by trapped air in your radiators, although it could also mean a frozen condensate pipe, water shortage in the header compartment, or low water pressure. Sometimes, gurgling sounds are just the hot water moving in the heater and not a reason to worry. However, if the noisy boiler becomes more prominent and frequent, it might need further attention.

If this sound is persistent, the first thing you should do is bleed the radiator. Sometimes, a gurgling sound can be mistaken for your boiler when instead, it could be from another appliance associated with it. Bleeding your radiator should be the first step for a few boiler noises covered in this guide.

Once your heating has been switched off and given enough time to cool down, follow these steps:

  1. Make sure you have a radiator key, if you do not have one in your home, you’ll be able to buy one from any hardware store. 
  2. With your radiator, put a towel and jug at the bottom of the bleed valve.
  3. Slowly turn the radiator key anticlockwise.
  4. Let the air retreat from the valve. You'll know it's working if you can hear a hissing sound.
  5. When the water is present through the bleed hole, close the valve.

It's essential to check your boiler's pressure after bleeding the radiator, as there's a chance it would have dropped significantly. Low boiler pressure will lead to further issues. If you've followed these steps and your boiler proceeds to make strange noises, then the issue resides elsewhere.

Alternatively, there are three main reasons and remedies to fix a gurgling boiler. There could be low water pressure, which in that case, you should look in your airing/boiler cupboard for the pressure gauge.

It should have compartments in red or green. The dial should be in the green section. If it's in the red part, the pressure is too low. If that's the case, you should add more water via the filling loop.

Secondly, if your circulation pump runs too quickly, you'll need to slow it down. You will need to contact a heating engineer to do this for you.

Finally, you should check for a blocked condensate pipe. It's highly likely for cold weather to form icicles on your pipes outdoors. To fix this, gently melt the icicles with warm water. However, if you are unsure that this is the cause of the gurgling noises, and you have bled your radiators, speak to a registered gas safety engineer.  

3. Vibrating noises

If you hear vibrating sounds, you might be lucky and only need the screws tightened, which is something you can do yourself. However, one of the other common causes of vibrating noises is something being trapped in the boiler flue. If you can, check your pipe on the outside of your properly to see if there is a blockage, just take your hand and place it over the vent, if you can feel air flow through the vent, it’s likely there is no blockage. If you’re still unsure, we advise to contact a gas safety engineer. 

If the noise returns, there may be something at fault with your boiler system.

If your pump is on an incorrect setting, it could be faulty and shaking inside the boiler, or there could be residue within your heat exchanger. Any built-up residue inside your boiler could cause hot water to overheat. This is dangerous for your boiler's health, and the only way to fix it is by calling a gas safe registered engineer who can conduct any relevant boiler repairs.

Find out more on boiler flues in our guide 'what is a boiler flue'.

4. Kettling noises

One cause of a noisy boiler could be kettling, which happens when the flow of water through the boiler slows down, causing the water to be heated too quickly and reach boiling point. When this happens, air becomes trapped in the system as a result of steam being generated, and gives off a whistling sound, hence being known as ‘kettling.’

A lot of the time this can be a result of circulating issues which means the water isn't pumping around the system properly, there could be a faulty pump, or be a result of system condition being poor. 

Kettling can be a serious problem that should be looked at by a gas safe engineer, but common causes include:

  • Limescale build-up
  • A leaking system
  • A faulty thermostat
  • Boiler overheating or faulty 
  • Faulty pump 

5. Rattling noises

The most common reason your boiler is making rattling sounds is there are loose bolts in your boiler. But these unusual noises can mean other things. Sometimes they come from blocked air in your radiator pipes, so your first step should be to try bleeding your radiator.

If all seems well, check for unclipped pipes or open valves. If you can find them, you can tighten and fix these yourself.

If you're unsure of the cause of the boiler noises, you should call an engineer. You may have a faulty pump or valve, which can't be fixed independently.

6. Loud humming noises

There are a few reasons why your boiler is making a humming or constant droning noise. Firstly, your central heating system might be affected. This can cause the hot water to move faster than it should. To fix this, you'll have to adjust the speed setting on the boiler pump.

Another reason is the boiler pressure is too high, which may need adjusting. If strange noises continue after adjusting the boiler pump and checking the central heating pipes, you may have a problem with your boiler fan, which will need to be looked at by a professional.

If you’re in luck, it could just simply be a loose component that needs tightening up. 

7. Clicking and tapping noises

If your hearing a clicking or tapping noise, and your boiler is struggling to fire up, it is most probably ignition failure. In this scenario, you will have no option but to call a gas Safe engineer as it could be related to the gas supply to your property.

8. Buzzing or whining noise

If you hear this sound, then you have every right to worry. 

Typically, it will be from worn pump bearings. If you can hear your boiler making a buzzing sound, or it sounds like it's moaning at you, you should listen to it.

Essentially, the whining noise is your boiler asking for help. It means it needs to get fixed immediately, and you must call a professional to do it.

9. Whooshing noise

Whooshing noises are prevalent in combi boilers. These noises coming from your boiler are made from a blocked circulation pump. 

You should call an engineer who can check for any blockages and diagnose the problem. 

Time to upgrade your boiler?

Time to upgrade your boiler?

Find a brand new, A-rated boiler that's perfect for your home in just 90 seconds

Get a fixed-price quote

Frequently asked questions

Hopefully, this guide has given you the confidence you need if your boiler makes unfamiliar noises. Remember, never attempt to fix anything yourself if you are unsure. You should always call a professional if you're in any doubt about the noises coming from your boiler. If left too long, your boiler will perish, and you'll have to invest in a new one.

If you feel it's time to let go of your noisy boiler, why not upgrade to a new boiler today? We can help you every step of the way in finding the suitable combi, gas or oil boiler for you.