7 Noisy Boiler Noises and How to Fix Them

A white home boiler

Last updated: July 20, 2021 at 11:27 am

Household noises are common and usually nothing to worry about. However, there’s one item in the home which easily takes the top spot for the most varied and worrisome amount, and that’s a noisy boiler.

A boiler can make countless different noises, some harmless and some that need some more attention.

In this article:

We’ll run through 7 different boiler noises, what they mean and how to fix them (if required).

Find the Cause of the Noisy Boiler

Before we start, it’s important to be clear that there’s no such thing as a silent boiler. All boilers make some noise, and this is entirely normal. However, if the noise starts to increase significantly, it’s a definite sign of trouble.

So:

If you’re noticing new noises, do not ignore them. While plumbers aren’t cheap, getting one in to fix a fault is still cheaper than replacing your boiler if the problem becomes too far gone.

What Is Making My Boiler So Noisy?

There are a lot of possibilities, so the quickest way to narrow it down is to determine the type of noise the boiler is making. First, take a quick look at the types of noise and potential causes below. Once you think you know what it is, you can take the time to read the correct section below.

Noise – Banging

  • Cause – Build-up of dirt on the heat exchanger. Pipes not fixed securely to the wall
  • Sign – Banging in your boiler or along the walls
  • Need Professional Help? – Yes, a powerflush is needed

Trapped air is responsible for a surprising number of sounds within a noisy boiler and even your pipes and radiators. Luckily, this is one of the problems that’s easiest to fix. You can’t bleed the boiler, but bleeding the radiators should release any air trapped in the system.

You’ll need a key, and if you don’t already have one, they’re freely available at hardware/DIY shops. Fit the key to the little nut on the end of the radiator at the top. You’ll hear a hiss of air, turn the key back when this sound stops. There’s a slim chance a blockage in the heat exchanger could also cause this, but air in the system is much more likely.

If bleeding the radiators doesn’t sort the problem, then a build-up of dirt on the heat exchanger is the likely culprit. You’ll need to get a heating engineer in at this point to perform a powerflush.

Noise – Dripping

  • Cause – A leak within the system. The most common cause is excessive pressure or old components.
  • Sign – Pools of water under the boiler or radiators
  • Need Professional Help? – Yes, the pressure will need to be reduced and/or components replaced

A dripping sound is always a problem, no exceptions! It will not get better on its own and could cause substantial issues if left unresolved. Get this professionally looked at asap.

Noise – Gurgling

  • Cause – Possibly air trapped in the system
  • Sign – Radiators have cold patches or don’t get warm at the top
  • Need Professional Help? – No, bleeding your radiators should fix it

Nine times out of ten, a gurgling sound from your boiler is caused by too much air in your central heating. This will stop the water from circulating properly, leaving cold spots on your radiator. This means the rooms won’t heat up as effectively, which will cause you more as you’ll have to leave the heating on for longer.

Luckily this is fixed by bleeding the radiators. For instructions on how to do it, check out the banging section above.

Noise – Humming

  • Cause – The pressure in your central heating might be too high
  • Sign – None
  • Need Professional Help? – Yes, you wouldn’t be able to reduce the pressure unless properly trained

If you hear a humming noise coming from your noisy boiler, then it’s likely the pressure is set too high. If your pressure is either too high or too low, it will not be running properly, and if it’s excessively high, it could even cause damage.

All boilers have a gauge where you can check the current pressure. If you’re not sure what your boiler should be set at, the best thing to do is to check your manual. As a good rule of thumb, though, most boilers run around 1.5 bar.

If your boiler is showing as higher than in your manual or in the red part of your gauge, you can bleed the radiators to lower the pressure back to the safe zone. It’s possible that bleeding the radiators could drop the pressure too low, and if so, consult your boiler’s manual to find out how to increase the pressure back to the optimum range.

If you’ve got your boiler back to the right pressure, or it was already there to begin with, and the boiler is still humming, it could be an issue with the pump.

The pump’s job is to force the water through the system from the boiler to the radiators where they’re needed. A lot of central heating pumps come with three speed settings, and if yours is set too high it may create that humming sound you’re hearing.

If you’re not sure why it’s at the level it’s at, and you know who installed your boiler, it might be worth querying it with them before changing the speed. There may be a good reason why it’s at that level.

If not, then have a quick look through your manual and see if there are any clues in there. If you still draw a blank, then you can try turning the speed down one level to see if the noise stops and if your heating still seems to work correctly.

Noise – Tapping

  • Cause – Sludge in the system or a loose component
  • Sign – None
  • Need Professional Help? – Yes, you’ll need to have your boiler checked and possibly powerflushed

Tapping noises in your boiler can be due to parts that were fitted badly or have worked themselves loose. You’ll need to locate the source of the noise and tighten up the part.

If tightening any loose parts doesn’t solve the problem, the tapping could down to a build-up of sludge or limescale on the heat exchanger. As explained in the banging boiler section, these build-ups need to be resolved by a professional performing a powerflush of the system.

Noise – Vibration

  • Cause – Loose brackets, open compartments, or the boiler might be shaking
  • Sign – None
  • Need Professional Help? – Possibly. You can close any obviously open compartments and try to tighten the brackets holding the boiler in place. If these don’t work, help is needed

Vibrating noises are one of the more difficult types to pin down. It’s easier if it was installed recently; it suggests it’s not been fitted properly to the wall. Get the engineer who installed it back in and have them tighten it.

If that’s not the cause, then look for any open compartments on the boiler and close them to see if that solves it. Failing that, look for any loose parts in the same way you would for a tapping sound.

If none of these things fix it, then it may be an issue with your central heating pump being set too high. See the humming section for more instructions on how to resolve it.

Noise – Whistling

  • Cause – Build-up of sludge or limescale on the heat exchanger.
  • Sign – None
  • Need Professional Help? – Yes, a powerflush should clear the contamination

A whistling noise tends to sound like an old-fashioned kettle; that’s why the issue that causes it is called kettling. It’s caused when limescale builds up on the heat exchanger. Once it happens, it isn’t something you can sort on your own. As with other issues, you need a heating engineer to perform a powerflush.

Once the engineer has fixed the problem, there is something you can do to make sure it doesn’t happen again. You can have the engineer fit a magnetic filter into your system, which will collect any contamination in your central heating and prevent it from reaching the heat exchanger. This will prevent kettling and improves efficiency.

Other Causes of a Noisy Boiler

Having the Thermostat Too High

You may love the heat, but if your heating is on full blast, the central heating will have to work hard to maintain it. Try turning your thermostat down by a few degrees and see if this stops it from being noisy.

If your house is too cold unless the heating is at the highest temperature, it’s a sign there is a problem in your system somewhere. Get a properly trained professional to look for the source of the problem.

Low Water Pressure

As explained in the humming section, problems arise if the pressure in your boiler is too low as well as too high. Check your manual to see what pressure it should be at, and then look at the pressure gauge. If it’s too low, follow the instructions in the boiler to repressurise it.

Frozen Condensate Pipe

Condensing boilers have a condensate pipe that takes away acidic waste water outside your home and directly down a drain. Because they’re outside, they’re prone to freezing over in freezing weather.

You can fix this yourself by pouring warm (but not boiling) water onto the pipe to thaw it out.

Conclusion

All boilers make some noise, but it shouldn’t be noticeably loud. If your boiler has a new loud sound, don’t ignore it, it’s usually a sign of trouble. The sooner boiler problems are addressed, the better.

Check out the list above for issues you can solve yourself but always call in the experts if you need more help. Gas is dangerous, so always treat it with respect.

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About the Author: AJ

AJ writes about living a quieter life, soundproofing tips and recommending the best quiet products here on Quiet Living.

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