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Boiler Banging Noises: What it means and how to stop it

Got a noisy boiler? Find out the different sounds your central heating system can make and how to get to the root of the problem.  

Your boiler will likely make a little noise when heating water and pumping it around your home, but a boiler making unusual noises could be a sign of a problem. If your boiler is making weird or loud noises, you shouldn’t ignore it because it could cause damage to your system and lead to an expensive repair bill.   

Below, we’ve shared the sounds your boiler or central heating system may make and whether you can fix the issue yourself or need to contact a Gas Safe registered engineer. 

1. Humming noises

If you can hear a humming noise coming from your boiler, the cause could be high boiler pressure. Another culprit of a humming boiler is a circulating pump set too high or fast. A loose or faulty component inside your boiler can also result in your system making humming noises. 

How to stop this noise

You can check whether your boiler’s pressure is too high by looking at the pressure gauge. If the pressure is too high, you can lower it yourself by bleeding your radiators. 

Thankfully, checking the circulating pump speed settings is straightforward and something you can do without contacting an engineer. If the pump is set too fast or high, you can fix this by lowering the speed. 

If lowering the boiler’s pressure and reducing the speed of the circulating pump doesn’t solve the problem, you should contact a Gas Safe registered engineer to remove the boiler casing and check the internal components. 

2. Vibrating noises

A boiler can sometimes make vibrating noises when the brackets are loose or when the exterior flue is blocked. The cause of vibrating noises can also be a build-up of sludge in your system, a shaking pump inside your boiler or, as we mentioned above, an incorrect setting for your pump. 

How to stop this noise

First, check to see whether the brackets are loose. If they are, you can tighten them yourself. If the cause is a blocked flue, go outside and check your external pipe for a blockage and remove it with your hands if it’s safe to do so. 

If you suspect the pump is shaking or you have a build-up of sludge inside your boiler, you must call a Gas Safe registered engineer to inspect your boiler for any possible faults. They can check the pump and put it right if it’s shaking or remove the sludge from your system.

3. Kettle noises

If your boiler sounds like a kettle when it comes to the boil, this is known as boiler kettling, which is one of the most common causes of a noisy boiler. Kettle noises can occur when debris or limescale builds up in your system, causing your boiler to overheat and generate steam. 

How to stop this noise

Limescale build-up can trap water, affecting the area around your boiler’s heat exchanger. A build-up of debris or limescale can also affect other parts of your central heating system. 

When left, the problem gradually gets worse and can lead your boiler to break down. A deep clean of your central heating system is usually enough to clear the debris or limescale, so you’ll need a Gas Safe registered engineer to carry out a powerflush using various chemicals. 

4. Gurgling noises

Most boilers make gurgling noises now and then, but not loud or constant noises. The most common reason for a gurgling boiler or central heating system is trapped air. However, incorrect water pressure or a frozen condensate pipe might be the culprit. 

How to stop this noise

If the cause is trapped air in your system, you can resolve this problem by bleeding your radiators. You should bleed your radiators as soon as possible or contact a Gas Safe registered engineer to do it for you if you’re unsure about doing it yourself.  

You can also check the pressure gauge on your system to see whether the pressure is too low or high. If it is, switch off your boiler and allow it cool before you re-pressurise it, following the instructions in your user manual. 

Another thing you can check yourself is the condensate pipe, which is usually a grey or white plastic pipe that runs from your boiler to an external wall. The water can freeze inside the condensate pipe where it is most exposed outside your home and cause a blockage during cold weather. You can thaw the frozen blockage using a hot water bottle, microwavable heat pack or some warm water – but do not use boiling water. If your condensate pipe runs inside your house and not externally, it’s unlikely to be frozen. 

5. Banging noises

Banging noises are often due to kettling which, as we said before, is usually thanks to a build-up of debris or limescale in or around your boiler’s heating exchanger. Limescale build-up is more common in areas with hard water. But if you can hear your pipes under the floor banging or tapping, they may be loose and need retightening. 

How to stop this noise

You should call a Gas Safe registered engineer to look at your boiler and diagnose the problem. 

6. Drone noises

If you can hear noises that sound like a drone or aeroplane taking off coming from your boiler, chances are your boiler has a faulty pump. Many things can cause this, such as the pump could be leaking, worn out or gathering debris.  

How to stop this noise

A Gas Safe registered engineer may be able to get the pump working correctly again, depending on the fault. If they can’t fix the pump, they might recommend a replacement pump, which will cost between £200 and £300, including installation. However, they may suggest replacing your boiler if it no longer works well and is over ten years old.