Day to day, you don’t tend to think about your boiler, it simply sits there out of sight getting on with its hot water and house heating business. That is, until it starts to make its presence known. While most central heating systems have a grumble every now and again, if your boiler suddenly starts to make an unfamiliar noise, you really do need to investigate. Not only is a noisy boiler annoying, but it can also indicate that something is wrong. And left alone, it could lead to more extensive and potentially expensive damage.
To help you understand ‘boiler speak’, we take a look at the various noises your boiler may make and what it could mean.
Check If the Noise is Coming From the Boiler
If you are hearing an unusual noise from your boiler, the first thing you need to do is check exactly where it is coming from. This may sound a little obvious, but it may not actually be coming from the boiler, but from the pipes or radiators it is connected to. Sounds can travel down the pipework, putting you off the scent so pinpointing the origin of that noise is key.
If it is not the boiler but your radiators or pipes, it is worth bleeding your system to see if it resolves the noise issue. If not, it’s advisable to call out a Gas Safe registered engineer to check everything over.
But if the sound is definitely coming from the boiler, then you’ve located the source and now need to identify the problem. Common causes of a noisy boiler include a build-up of limescale, an air blockage, low water pressure, insufficient water flow and overheating.
Check the Boiler Error Codes
One quick way to know whether there is a serious problem causing the noise is to check your boiler’s error codes on its digital display. Modern boilers are designed to display an error code if a problem or fault is detected, while a more serious issue will cause the safety lockout feature to be triggered or even shut the whole boiler down.
However, if there is no indication on your boiler’s display that there is a problem or a specific fault has been detected, then there is another way to identify the potential issue. And that is based on the type of sound you are hearing coming from your noisy boiler.
Different problems can create a different noise, including a distinct gurgling, vibrating or whining. We take a look at the most common noises that your boiler may make, what it means and what you should do to put it right.
As your boiler is continually heating water and then pumping it around your home, a little gurgling can be expected. But if the gurgling is happening more frequently, or is getting louder, then it is worth investigating. The gurgling noises in your boiler system may be caused by some trapped air which, if left unresolved, can lead to uneven heating and can cause your boiler to use more gas or work overtime to warm your home, and so increase your energy bill. Gurgling boiler noises can also be caused by a frozen condensate (wastewater) pipe, which can damage your boiler.
If your boiler is making a gurgling sound, you can:
Bleed the system – bleeding your radiators will get rid of any trapped air in your boiler system and should stop the noise if trapped air is the problem.
Check the water pressure – low water pressure can also cause gurgling in your boiler so check the boiler’s pressure gauge. The correct pressure should be between 1 and 1.5 bar so if it’s below this, then repressurising the system could do the trick. If you find the pressure is dropping regularly, get a gas safe registered engineer to do a full check.
Consider the circulation pump – a gurgling noise could also indicate a problem with the circulation pump, which is usually found inside your boiler. You’ll need an engineer for any repairs.
Check for a frozen condensate pipe – the condensate pipe will typically be on the outside of your home and if frozen, you should be able to thaw it with warm (not boiling) water.
Buzzing or Whining Noises
A persistent buzzing or whining should not be coming from your boiler and is usually a sign of an internal fault. Possible causes can include a defective burner, vibrating fans or worn pump bearings.
Buzzing or whining can indicate a serious fault within your boiler, and you should not attempt a home repair. You will need a skilled gas safe engineer to come out to correctly diagnose and resolve the problem.
Vibration sounds coming from your boiler can be caused by several issues, including a malfunctioning pump vibrating inside its casing, or a pump on too high a setting. It can also be caused by a build-up of sludge inside the boiler, which if left, can lead to over-heating – causing your boiler to make a kettle boiling sound.
A build-up of sludge – this can become serious and so will need to be removed which requires the attention of a qualified heating engineer. A faulty pump will also need the attention of a professional.
Check the boiler intake flue – a blocked air vent can also cause a vibrating noise and is simple to rectify. Check the outside pipe and remove any debris such as leaves that may be obstructing the airflow. Check the air filter – the boiler air filter may also be blocked so read your boiler manual to see if it is possible to clean this part yourself or call out a gas safe engineer.
Other Common Noises From Boilers
As well as gurgling, buzzing and vibrating, your boiler can be vocal in other ways. Below are other common noises that may come from your boiler and what the sounds could be telling you.
Rattling sounds coming from your boiler may well indicate that there are loose objects inside, knocking against each other when the central heating system is turned on.
Alternative causes for the rattling can include air in the pipework, which can usually be resolved by bleeding your radiators. Loose valves can also rattle as well as pipes which may not be clipped on properly. Another cause of rattling can be a faulty pump or non-return valve so if bleeding your radiator or checking connections has not resolved the rattle, call out an expert to check the heating system over.
Loud humming noises
Water heaters can rumble and hum if there is a build-up of sediment within the cylinder, however loud and persistent humming can be an indication of very high pressure of incoming water within your boiler. Check the pressure and adjust if necessary and check your tap washers as they could also need replacing. Humming can also indicate too high a setting on your boiler’s pump, so water is travelling too fast around your hot water and central heating system. If in any doubt about a humming boiler, call out an engineer.
Boiling Kettle Noises
If your boiler is making sounds like a boiling kettle, one of the most likely causes is air trapped inside the central heating system, which can be rectified by bleeding your radiators to release the air. If, after bleeding your radiator, the boiler kettling noises persist, it could indicate a build-up of limescale or debris in the system, a possibly in the boiler and on the heat exchanger, restricting waterflow and leading to a build-up of steam, causing the kettling noise. If this is the case, your best option is to get an engineer to do further investigations and if need be, clean out the system.
Banging or popping noise from your boiler is also another likely indicator of a build-up on limescale, deposits or sludge in the heat exchanger, especially if you live in hard water areas. You may also hear very loud bangs as big air bubbles trapped inside the boiler pop – it sounds pretty dramatic, but it doesn’t mean your boiler is about to explode. You will need to call out an engineer though, as it needs a qualified expert to clear your clogged up boiler out.
Tapping is another sound related to a kettling boiler, and again, is caused by limescale build-up on the surface of the heating exchanger. It may get louder as the water is pumped around your central heating system. Trapped air bubbles can also cause a tapping sound as they expand and then collapse. To be safe, call out an engineer for tapping sounds so it can be diagnosed correctly.
Is a Noisy Boiler Dangerous?
While a noisy boiler at best can be mildly annoying and, at worst, pretty scary, it is unlikely to be dangerous. But that doesn’t mean it should be ignored. Noises do indicate something may not be working as well as it should, or there is air, limescale or debris trapped inside the boiler system. And leaving your boiler to its noisy antics could mean you are storing up trouble that could lead to expensive repairs. If none of the quick fixes outlined in this blog work, and your boiler keeps making a noise or you are in anyway concerned, get a gas safe registered engineer on the case.
Is it Normal for a Boiler to Make Noise?
It’s not unusual for your boiler to make the odd noise as it works to keep your home warm and your hot water on tap, and in most cases shouldn’t be a cause for concern. The time to sit up and listen if the noises come on suddenly, are happening frequently, lasting longer or getting louder. These are a sign that something may not be quite right. You can do some quick checks and fixes for some of the most common causes but there are occasions when you should attempt a repair yourself. If this is the case, or you are in any doubt, the best way to deal with a noisy boiler is to call a heating engineer out.
- Why is my boiler making noises? – Viessmann