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What different noises coming from your boiler mean

The reasons behind strange noises coming from your boiler

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Is Your Boiler Making Weird, Loud Or Unexpected Noises?

Wanting to know why your boiler is making a strange or loud noise? Well this isn’t a question that is easily answered, there are many different types of noises your boiler can make with a variety of different reasons behind each. An easy way to put it would be if your boiler is making noise similar to a Marilyn Manson song, then your best bet is to run for the hills and call an engineer! Jokes aside, every boiler is expected to make a certain level of noise whether it’s the pipes creaking from thermal expansion or humming as the system starts up. Each boiler is different and will make different noises depending on its model, age and installation. No one will be able to definitively say why a boiler makes a certain noise without inspecting the system beforehand; in this article we will try to detail some of the causes behind common noises and how to address them.

Boiler kettling

Kettling refers to a whistling noise a boiler can make due to limescale build up or a faulty part. It is called kettling because it resembles the whistling sound a stovetop kettle makes when the water inside reaches its boiling point. 

Boiler kettling is normally due to a build up of limescale around the heat exchanger, this causes the heat exchanger to overheat which in turn heats the water past its boiling point. When the water is heated in this manner it turns into steam which then escapes, creating the whistling noise known as kettling. Limescale build up isn’t the only thing that causes kettling to occur, it can also be caused by other debris building up around the heat exchanger. When debris is responsible for the boiler kettling then your system will need to be power flushed by a professional in order to be certain the system is cleared and clean. 

Kettling affects the efficiency of the boiler as it will take more energy to heat the same amount of water, leading to higher energy bills. It can also damage other internal components due to the overheating of the heat exchanger. You will need a gas engineer to attend your property so they can officially diagnose the problem, clean / repair any parts, replace any parts if necessary and also potentially install a limescale inhibitor or a dosing pot to reduce the likelihood of the problem recurring.

Vibrating / rattling noise

This is normally the boiler noise that is fairly easy to address and solve. Most vibrating or rattling noises coming from your boiler system are resulting from loose components that simply need to be tightened. Components that could need tightening vary greatly and could be anything from a loose pipe bracket, a loose valve or an internal component behind your boiler casing.

When trying to solve this issue yourself we recommend trying to figure out where the noise is coming from and once located tightening the screw in the area to see if the noise ceases. If the noise is coming from the boiler itself and is behind the boiler casing you will need to book an appointment for a gas engineer to diagnose and fix the problem. This is because it is illegal to do so without being a member of the Gas Safe Register and holding the correct qualifications for the appliance in question.

The vibrating noise could also be caused by a malfunctioning pump that is on a too high setting, this would then rattle against its case giving off a loud rattling sound. Any air trapped within a boiler system can also lead to an occasional vibrating noise, this is normally solved by bleeding your radiators to remove any excess air inside the boiler system.

Banging noise

Another noise often resulting from boiler kettling is a loud banging or cracking noise from inside the boiler itself. When the water flow in and around the heat exchanger is restricted or blocked, it can result in big air bubbles becoming trapped at certain parts inside the system. Once the air bubbles eventually break free or pop it regularly produces a harsh banging sound. 

Another factor that may cause a large banging noise is when the initial combustion process occurs. In this part of the heating process air is drawn in to fuel the combustion, if your boiler is fairly air tight it will create a suction effect which can move the casing of the boiler creating a large banging noise. This may make you jump but don’t fear, boiler noises like these don’t mean your boiler is going to explode despite how scary it may sound. 

As mentioned previously, you will need to organise for an engineer to solve the matter. If not the kettling can damage internal components of your boiler leading to a lot of maintenance or a complete replacement.

Solving the problem may be as simple as installing a water softener to prevent the build up of limescale, or it may involve a more complex solution. This is why we always recommend calling an engineer to investigate the matter.

Gurgling noise

Gurgling noises are usually produced by two different factors. Excess air trapped inside your boiler is a common and easily solved problem with boilers; bleeding the radiators on your property should remove any excess air within the system and prevent this from happening.

Alternatively if the weather is cold then it may be because of a frozen condensate pipe. The gurgling noise omitted from a frozen condensate pipe is normally fairly quiet so probably won’t be noticeable when paired with the general sound of your boiler running. For more information on frozen condensate pipes read this article.

Banging noise

Another noise often resulting from boiler kettling is a loud banging or cracking noise from inside the boiler itself. When the water flow in and around the heat exchanger is restricted or blocked, it can result in big air bubbles becoming trapped at certain parts inside the system. Once the air bubbles eventually break free or pop it regularly produces a harsh banging sound. 

Another factor that may cause a large banging noise is when the initial combustion process occurs. In this part of the heating process air is drawn in to fuel the combustion, if your boiler is fairly air tight it will create a suction effect which can move the casing of the boiler creating a large banging noise. This may make you jump but dont fear, boiler noises like these don’t mean your boiler is going to explode despite how scary it may sound. 

As mentioned previously, you will need to organise for an engineer to solve the matter. If not the kettling can damage internal components of your boiler leading to a lot of maintenance or a complete replacement.

Gurgling noise

Gurgling noises are usually produced by two different factors. Excess air trapped inside your boiler is a common and easily solved problem with boilers; bleeding the radiators on your property should remove any excess air within the system and prevent this from happening.

Alternatively if the weather is cold then it may be because of a frozen condensate pipe. The gurgling noise omitted from a frozen condensate pipe is normally fairly quiet so probably won’t be noticeable when paired with the general sound of your boiler running. For more information on frozen condensate pipes read this article.

Clicking or tapping noise

Another byproduct from your boiler kettling may be a clicking or tapping noise. When the air bubbles created by the boiler kettling move throughout the system they can expand and contract, when they do this it can cause the pipes to do the same which creates the clicking or tapping noise heard.

Although if this noise is consistent and your boiler isn’t heating up as it should it may be due to a faulty ignition. Ignitions will make a clicking noise when trying to ignite its fuel source, it will continually make this noise if it doesn’t successfully light. An engineer will be needed to fix this problem due to it being a gas component and therefore a Gas Safety licence is needed to legally do so.

Humming noise

A humming noise is regularly a result of having too high boiler pressure. If the boiler pressure is too high it could make the valves give off a whiney humming noise as the pressure tries to escape. On the other hand it could cause the water to move around faster than it should, producing a humming sound throughout the whole system.

Persistent ongoing hums are normally caused by a pump which is on too high of a setting (as seen in the rattling noise sector), or by an internal fan inside your boiler due to the bearings wearing out which will happen over time.

Every system is unique

Please bear in mind that all boilers are different and there is a wide variety of different noises that a boiler can make, each noise has a plethora of reasons as to why it could occur. The reasons for the noises stated in this article are simply the most common explanations that we witness daily as a company. The description of the sounds is completely subjective to your own perception e.g. a humming noise to one person may be described differently by another. We always recommend contacting a qualified professional to diagnose and fix any problems you have with your boiler system, for any questions or to book an appointment please call our 24/7 customer service helpline (0207 9989 005).

Every system is unique

Please bear in mind that all boilers are different and there is a wide variety of different noises that a boiler can make, each noise has a plethora of reasons as to why it could occur. The reasons for the noises stated in this article are simply the most common explanations that we witness daily as a company. The description of the sounds is completely subjective to your own perception e.g. a humming noise to one person may be described differently by another. We always recommend contacting a qualified professional to diagnose and fix any problems you have with your boiler system, for any questions or to book an appointment please call our 24/7 customer service helpline (0207 9989 005).