Some sounds are perfectly normal for a boiler to make when it’s working hard heating your home and hot water.
You can expect to hear some sounds from the pilot light being ignited, or the pump circulating water around your heating system – and these aren’t any cause for alarm.
But if you’ve suddenly noticed your boiler making unfamiliar, loud or strange noises, they could indicate a problem, and are a cause for concern.
If it sounds like an aeroplane is taking off in your utility room, or your boiler is banging, whistling, or gurgling, you’ll want to get to the bottom of what’s going on – and fast.
You should never ignore warning signs that your boiler is on the blink, because it could pose a safety risk. But even if it isn’t a dangerous fault, ignoring a problem will result in a more expensive repair bill, or worse, down the line.
In this guide, we explain some of the possible causes of some common, but abnormal noises, that might be coming from your boiler.
Where’s the noise coming from?
First things first, where’s the noise coming from? Whilst this might sound like a stupid question, sometimes noises may travel and echo through your heating system.
The noises might not be coming directly from the boiler itself, but rather from your pipes, radiators or a tank or cylinder.
It’s easier to identify the problem when you pinpoint precisely where the noise is coming from.
Check for a fault code
The next step is to check whether your boiler is showing a fault code.
Most modern boilers, particularly combi boilers, have a digital display which will show a boiler fault code when your boiler encounters a problem. The code helps to identify the cause of the problem and indicates what action should be taken.
All boilers display error codes differently, so depending on your model, the error code itself will vary.
If your boiler is showing a fault code, the first step to take, is to check your boiler’s manual.
Strange or unusual noises that your boiler might make
Here are the most common abnormal noises that you may hear from a boiler that has a problem:
- Gurgling noises
- Banging or whistling noises
- Whooshing noises
- Humming or vibrating noises
- Aeroplane or droning noises
If you hear any of these noises coming from your boiler, read on and we’ll explain what might be causing them.
1. Noisy boiler: Gurgling boiler noises
If your boiler is making gurgling noises, this could be a sign that air has become trapped inside the heating system and is mixing with the water. Thankfully, this isn’t usually a big problem, and can sometimes be resolved by simply bleeding your radiators.
Fixing the problem: bleeding your radiators
To bleed your radiators, you need to start by turning your heating off and allowing your radiators to cool. Place towels on the floor under your radiators and put a container under the bleed valve.
Using your radiator key, release air from the bleed valve by slowly turning it anti-clockwise to release air. You should hear a hissing sound as the air escapes.
Keep releasing air from the valve until you can no longer hear air escaping and some water begins to trickle out. When this happens, close the valve quickly.
Once you have released the trapped air from your radiators, check your boiler pressure and switch the heating back on.
If bleeding your radiators has done the trick, that’s great. But if you’re still noticing gurgling sounds, you should contact a Gas Safe registered engineer for help.
2. Noisy boiler: Banging or whistling boiler noises
If your boiler is making banging or whistling sounds, chances are you’re experiencing ‘boiler kettling’. It’s called ‘kettling’ because it sounds like a kettle boiling, and it’s a common cause of a noisy boiler.
Not only does a kettling boiler sound like a boiling kettle, but it’s also much the same process behind it!
Despite the misleading name ‘boiler’, the water in your boiler shouldn’t actually boil. Water is typically heated to around 70 °C before being pumped around your home to be used by your radiators and hot taps.
But if the flow of water is slowed down for some reason, the water can heat too quickly and reach boiling point (100 °C).
If this happens, steam is generated, and air becomes trapped in your heating system. You’ll start hearing whistling, banging, popping and gurgling sounds.
There are several reasons why water might be being pumped around at a slower rate and reaching boiling point:
Possible cause of kettling: Limescale build up
Limescale build-up is one possible cause of kettling, and it’s a common problem for homes in hard water areas.
When limescale and ‘sludge’ accumulates in your heating system’s pipes, it will block the flow of water. By slowing the flow of water, it can be overheated by your boiler – causing kettling sounds.
Pipes blocked by limescale and sludge is also a common reason for your radiators developing cold spots.
Possible cause of kettling: Faulty thermostat
Another potential cause of kettling could be a faulty thermostat. A broken thermostat can give an incorrect reading to your boiler, causing it to over-heat the water.
Possible cause of kettling: Damaged pump
Another possible culprit is if your boiler pump is damaged. The boiler pump’s job is to push water through your heating system at the right speed to heat the water to the correct temperature.
If the pump develops a fault, it’s likely that water will be pushed at a slower rate, and will be overheated by the boiler.
How to stop boiler kettling
Boiler kettling is not something you can deal with yourself. It can be dangerous, and you should call a Gas Safe engineer to investigate what the cause of the kettling is.
If the cause of the kettling is limescale or sludge build-up, a chemical clean or power flush should do the trick. But if you have a faulty part, such as the pump, this may need to be replaced.
3. Noisy boiler: Whooshing boiler noises
Whooshing or vibrating noises from your boiler can be alarming, but thankfully the problem is usually with the air supply and sounds much worse than it is.
There are two common reasons for whooshing noises originating from a boiler.
Possible cause of whooshing noises: Air intake pipe blockages
The first common cause of whooshing sounds is a blocked air intake pipe. The air intake pipe is attached to the back of the boiler and leads outside of your home. If dirt and debris block the pipe, this can cause a whooshing sound.
Possible cause of whooshing noises: Air filter blockages
The second common cause of whooshing noises is a blocked air filter. Air filters are usually located inside your boiler. They can get blocked up by the buildup of dust and debris. If this happens, the passage of air is blocked, creating a whooshing sound.
How to stop whooshing noises
Whether the issue is with the air intake pipe or the air filter, you should call a Gas Safe engineer to fix the problem.
4. Noisy boiler: Humming or vibrating boiler noises
If your boiler is humming or vibrating, there are a few potential causes for this, including the following:
Possible cause of humming noises: Water pressure that is too high
High pressure is one of the biggest culprits of humming or vibrating noises. You can use the pressure gauge on the front of the boiler to check that the pressure is under 1.5 bar when the radiators are cold.
Possible cause of humming noises: The boiler’s pump is seized up or is running too fast
Another common culprit of a humming boiler is a problem with the boiler’s pump. If it has seized up or is operating too fast, it can cause vibrations and humming.
Possible causes of humming noises: A loose component such as the bearings on the boiler fan
Another issue that can create a humming noise is if the bearings within your boiler fan are on the way out.
How to stop humming noises
If the humming is caused by high pressure in your heating system, you may be able to resolve this by reducing the pressure by removing some of the water in the system.
If this doesn’t work, or it’s not a high pressure issue (you’ve checked your pressure gauge), you will need to contact a Gas Safe engineer for help.
5. Noisy boiler: Aeroplane or droning noises
One of the more disconcerting boiler noises is when your boiler sounds like a drone or aeroplane is taking off. The usual cause of this is a faulty pump.
How to stop aeroplane or droning noises
The most common resolution here is to have a broken boiler pump replaced. You should contact a Gas Safe engineer as soon as you hear your boiler making an aeroplane or a droning noise.
How to avoid boiler noises
Prevention is better than cure, so to avoid having problems in the future, you should ensure that you have your boiler serviced annually by a Gas Safe engineer.
Regular servicing reduces your chances of developing noisy faults because any required maintenance will be carried out proactively.
Research by Which? Found that around two thirds of boilers that are serviced every year never need a repair. This number drops dramatically as you increase the time between services, so spending a bit on a boiler service could potentially save you a much bigger repair bill in the future.
Hopefully this article has helped you to understand your boiler a bit better, and you may have identified a possible cause of a strange new noise.
It may be that there’s a quick fix to your problem. But unfortunately, boilers don’t last forever.
If your boiler is in its golden years; is out of warranty; or always seems to be on the blink – it might be time to consider a boiler replacement.
Why not contact The Heating People to book your free survey?