Every boiler makes sounds, but it’s important to know which to take seriously.
Although some noises, like gurgling, might not cause immediate issues, others, such as banging or whining, could indicate a more serious problem that could lead to costly repairs or system failure if left unchecked.
New research* commissioned by BOXT (https://www.boxt.co.uk/) has revealed that nearly one in five Brits (18%) have faced heating and hot water problems in the past month - with Londoners (29%) and Scots (19%) the worst hit.
Of the 2,000 UK adults independently polled by the fixed-price boiler specialist, over half (56%) admitted they ignored warning noises from their boiler before the issue escalated.
“When your boiler starts making unusual new noises, it can be a bit worrying, especially when we rely on them so much to keep our homes warm and provide hot water,” says Adam Knight, Lead Engineer at BOXT (https://www.boxt.co.uk/).
“As an expert in heating systems, I've heard every sound imaginable and learnt how to speak fluent ‘boiler’ over the years.”
“Every whistle, bang and gurgle is a clue to what’s going on inside.”
“When you hear strange sounds coming from your heating system, it’s easy to panic. But not all noises are cause for alarm.”
Knight explains the 9 most common noises your boiler might make, what they mean, and the best ways to handle them.
1. Loud banging noises - it could simply be trapped air
Loud banging or popping sounds are often a sign that air has built up inside your boiler’s heat exchanger or central heating system. This can cause overheating and create pressure build up, which results in the banging noise.
Other possible causes could be system blockages, scale or sludge build up or even ignition issues.
Avoid this mistake: If left unchecked, it could damage your heat exchanger, leading to expensive repairs or a full replacement.
How to fix: Bleeding air from the system via radiators and ensuring correct operating pressures (topping up your boiler pressure) can solve this. If in doubt, call in a Gas Safe heating engineer to check the boiler and system over.
2. Gurgling noises - trapped air, frozen pipes or low water pressure
Gurgling sounds are often a sign of trapped air in your radiators or low water pressure, although they could also indicate condensate pipework blockage (commonly in winter months).
How to fix 1: Start by bleeding your radiators (https://www.boxt.co.uk/boilers/guides/how-to-bleed-a-radiator). It's essential to check your boiler's pressure after bleeding them, 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.
How to fix 2: As a general guide, the pressure should be between 1-1.5 bar when the system is off and can rise to up to 2 bar when the heating is on. If the pressure is too low, you may need to top it up using the filling loop or key.
How to fix 3: If the weather’s been really cold, check to see if your condensate pipe has frozen. To fix this, check where the pipe under the boiler (usually made of white plastic) exits the house. If it goes to a drain, make sure it’s not blocked. If it is frozen, and you can safely access the pipe, try and gently melt the trapped ice with warm, not boiling, water.
Avoid this mistake: Ignoring the pressure gauge. If your pressure is low, simply continuing to use the boiler without fixing it can lead to damage. Persistent gurgling can also indicate more serious issues at play.
3. Vibrating noises - loose components or blockages
If you hear vibrating sounds, you might be lucky and only need the screws tightened, which is something you could possibly do yourself.
How to fix: Start by checking for any loose screws on the external case of the boiler ONLY. If that doesn’t solve it, something could be loose within the boiler. Never remove the boiler case yourself.
Avoid this mistake: If there’s no obvious visible reason for the vibrating noise don’t leave it and don’t try and fix it yourself. The only way to fix it is by calling a Gas Safe registered engineer.
4. Kettling or ‘whistling’ noises – your boiler could be overheating
If you hear a kettling - or ‘whistling’ noise, it’s usually a sign of limescale buildup inside the heat exchanger, restricting the flow of water. It causes the water to overheat and boil.
Avoid this mistake: Never ever try to "flush" the system with chemicals on your own.
How to fix: Kettling can be a serious problem that should be looked at by a Gas Safe engineer.
5. Rattling noises - loose components or system debris
Rattling noises can indicate loose or poorly supported pipework, or even small amounts of debris in the boiler pipework or air trapped in the system.
How to fix: Check for unclipped or unsupported pipes that are visible. You may feel comfortable fixing these yourself. Trapped air can be bled via radiators, or manual air vents usually above boilers or in airing cupboards. If there is debris in the system it may need draining or flushing. Always consult a qualified plumber or a Gas Safe engineer for advice.
Avoid this mistake: If the rattling sounds like it’s coming from inside the boiler, never ever unscrew the casing and try and try and locate it yourself. Legally, this should only ever be done by a Gas Safe qualified engineer.
6. Loud humming noises - pump, water flow or fan issues
A loud humming sound could indicate an issue with your pump or there’s a problem with water flow in the system. It could be too fast, too slow, or even blocked.
Modern fans in boilers can also create humming noises, if the noise has changed or become louder when the boiler is in operation it could indicate a problem with the fan bearings or airways.
How to fix: Call in a professional for this one. The speed setting on the boiler or system pump may need adjusting if applicable. They would also take a look at the fan if suspected.
7. Clicking and tapping noises - ignition failure
If you're hearing a clicking or tapping sound and your boiler is struggling to fire up, it is most probably ignition failure. Possible issues can be low gas pressure, blocked gas injectors, an ineffective gas valve or faulty flame sensor. It could even be related to the gas supply to your property.
Avoid this mistake: Do not attempt to fix yourself. Contact a Gas Safe registered engineer to diagnose the problem and repair the faulty component. The only thing you could do is check the gas meter control valve hasn’t been accidentally turned off (commonly this can happen if they are located under sinks and in storage cupboards)
8. Buzzing or whining noise – your boiler’s “Cry for Help”
A buzzing or whining sound often comes from a faulty fan or pump that’s working harder than it should. This could also indicate something is blocking the system.
Avoid this mistake: Don’t ignore this noise. If you can hear your boiler making a buzzing sound, or it sounds like it's moaning at you, listen to it - you have every right to worry.
How to fix: Essentially, the whining noise is your boiler crying for help. It means it needs to get fixed immediately by a Gas Safe registered engineer.
9. Whooshing noise – blocked circulation pump
Whooshing noises are common in boilers. These noises coming from your boiler tend to be made from a blocked circulation pump.
When a circulation pump is blocked by sediment or debris, the water struggles to flow smoothly, leading to a rushing or whooshing sound as it tries to pass through the blockage.
How to fix: Check for trapped air. Sometimes, a whooshing noise can be caused by trapped air in the system, which can be resolved by bleeding the radiators.
If the noise persists after this, call a Gas Safe registered professional.