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Last Updated on January 22, 2021

Boiler Making Noise – Rumbling, Loud, Banging, Vibrating & Whistling

Zac Houghton

Zac Houghton

Construction expert and founder of Loftera.

If you start to hear your boiler making noise, whether it’s a low rumble or full-on banging noise, it can be a serious cause for concern. Whilst it’s true that you’ll find boilers making bubbling or gurgling sounds from time – i.e. the sound of water filtering into the system – any boiler noises that are particularly loud or unfamiliar can point towards serious malfunctions and possibly major health and safety concerns.

It’s stressful when you notice anything going wrong with your heat and hot water, but if you’ve suddenly noticed your boiler making strange noises, you should act as fast as possible. Not only will diagnosing what’s wrong with it help put your mind at ease, but the sooner you do the more likely you are to avoid further, more costly repairs or worse.

With that in mind, we’ve put together a quick guide on how to determine which noises could mean what, and whether your noisy boiler just needs a little TLC or something more major.

boiler making noise

Table of Contents

First things first, where’s it coming from?

This might sound like an obvious answer: “my boiler is making a noise, duh!”; however, whether it’s an old conventional tank or a modern but noisy combi boiler, all systems have various different parts and your problem can be isolated quicker if you pinpoint exactly what part the noise is coming from.

Check the error codes

Next is another, even simpler step: check for any error codes on your boiler. Most modern systems, combi boilers in particular, come with a digital display where you control all of your settings, timers etc. This is also where problems picked up by the boiler’s monitoring technology may appear, which again will help you more quickly ascertain what the problem might be.

Now, on to what noises might mean what.

Boiler making gurgling noise?

If this is this case and the sound is louder than the usual bubbling noises you tend to hear when the heating or hot water is on, then you may be suffering from low water pressure. A relatively straightforward step would be to bleed the system.

This noise is often caused by pockets of air trapped throughout the system, so bleeding the system can help release this, allowing you to start from scratch. Here’s how:

  1.   Open all radiator valves and run the heating on full temperature for 10-15 minutes.
  2.   Turn the circulation pump off and wait for the radiators to cool.
  3.   Bleed the radiator closest to the boiler, making sure to lay down some absorbent sheets or towels, until water comes out.
  4.   Repeat this for each radiator,
  5.   Turn the boiler on and check the water pressure – it should be between 1.5 and 2 bars.

Whilst bleeding your individual radiators may be the method most people are familiar with, many modern boilers come with a bleed screw/grommet on their pump, allowing you to similarly release trapped air from this point.

Boiler making vibrating noise?

If your boiler is making buzzing noises or seems to be vibrating, this can point towards a number of different issues of varying severity. This can range from something as simple as loose brackets – which is an easy DIY job – to a problem with internal parts, such as worn pump bearings, faulty burners or the boiler fan itself.

If tightening brackets doesn’t get rid of the buzzing/vibrating noise, then it is likely that one of these problems is the cause. However, as with any serious boiler repair, this would require calling out a Gas Safe Registered engineer.

Boiler making banging noise?

If your boiler is making loud banging noises, there could be a problem with your thermostat or, equally, a build-up of limescale on your heat exchanger. If there is a build-up of debris, you’ll need to carry out a power flush. A power flush removes any blockages within your system and allows for hot water to move freely around your home.

Again, if the noise is significant, it’s best to be on the safe side and get in touch with a qualified professional.

Boiler making whistling noise?

Is your boiler making whistling noises? This is most likely a sign of limescale build up in your pipes and/or heat exchanger. The more clogged your pipes, the less water that is able to pass through, causing your heat exchanger to fill up with water and overheat, gradually releasing it as steam – hence it whistling like a kettle.

Whilst some build of limescale over time is expected, it can be worse if you live in ‘hard water’ areas of the UK. Regardless of whether this applies to you, not only will it affect your energy efficiency, but leaving the limescale to continue building up can seriously hurt your boiler, so be sure to get it fixed ASAP if you want to avoid further damage and prolong your boiler’s lifespan.

To remove the limestone, you need to run a hot water flush using a chemical solution known as central heating inhibitor: we will give you a brief summary of the process shortly and the solution is widely available should you choose to DIY.

If the build-up is significant and it has damaged your heat exchanger beyond repair, you may need to buy a new one – these can cost upwards of £500 a pop though, so act early if you want to avoid a costly repair.

Boiler making clicking/tapping sounds?

This is also one of the most common cases you’ll come across. If you hear your boiler clicking, the most likely cause is that the boiler is struggling to ignite. This can be for a number of reasons: no gas, low pressure, faulty valves or thermocouples, or even just a dirty pilot light.

While the lattermost is an easy job – just carefully remove any dirt and debris using a cloth and perhaps a wire brush – faulty valves or significant drops/increases in pressure can point towards a leak. Be sure to check for any staining around your boiler and if you can smell any gas. If you do, call the Gas Emergency helpline immediately: 0800 111 999.

Hopefully, this isn’t the case and even if you happen to have a faulty part, it’ll simply be a case of having a qualified professional come to carry out the repairs/replace the part.


Boiler sounds like it’s on when it’s off

As mentioned, there are lots of natural sounds that you can expect to hear from a boiler and they shouldn’t cause you any trouble – a lot of the time, it’s simply water moving from area to another and echoes can be sent throughout the pipes.

Another common source of noise is what is known as the ‘pre-heat’ function. In combi boilers specifically, this is basically the sound of the heat exchanger firing up intermittently, making sure that it is ready to produce hot water when you need it.

However, if the noise is constant/every couple of minutes, this could be a sign of ‘short cycling’. This is when your thermostat detects the heat exchanger is cooling when your home has already achieved the desired temperature. This means that it is constantly trying to heat up that small amount of water, not only overworking your boiler but likely increasing your bills. This may require you to repair/replace your heat exchanger.

Boiler making humming noise when heating on – is that normal?

In short, yes. Your boilers circulating pump is what sends hot water around your house and it is fairly typical for you to hear some humming when using the heating or running a shower etc.

However, if the humming is particularly loud, this could be a sign that your pump is running too fast. If setting it at a lower speed doesn’t remedy this, then similar to our point about vibrations, check for any loose parts/brackets and perhaps check your boiler pressure – this should never be above 15 psi.

How do I flush my boiler/central heating system?

  1.   First, switch off your boiler and the water intake valve.
  2.   Next, place a bucket under the drain-off valve and proceed to drain the system until it’s empty.
  3.   You are now ready to power flush (power flushing devices can be purchased online or in hardware shops). Add your cleaning fluid into the device and switch it on to start circulating the solution around your system.
  4.   Turn on your boiler to heat the chemicals until it reaches 45°. Reverse the flow every 10 minutes to achieve the most thorough cleaning.
  5.   Keeping all other radiators closed, flush a single radiator at a time, repeating this process until finished.
  6.   Now open all radiator valves and allow the hot flush to flow freely. Once you have clean running water coming out, add the neutralizing agent to get rid of any remaining chemicals.
  7.   Finally, run one more complete flush and add a corrosion inhibitor – also widely available. Once completed, close all valves while disconnecting the power flush unit. You can then reopen the valves and turn your water supply back on at the mains.

For a more comprehensive explanation, be sure to check out this helpful video.

We hope you found this quick guide helpful – it is by no means comprehensive, so be sure to do your research surrounding whatever noise your boiler is making – and remember, when in doubt it’s worth a call out.

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