Boiler Making Noise: Causes & How To Fix a Noisy Boiler

James Elston
Written by James Elston
Updated on 22nd February 2024
Posted on 6th February 2024
Boiler Making Noise: Causes & How To Fix a Noisy Boiler

Boiler Making Noise? Here are the Reasons Why & How To Fix Them

noisy boiler

Ask any repair engineer near you, and they will tell you one of the most common complaints by customers is that their boiler is making a loud noise. The best way to describe this noise is “banging”. Regardless of how you describe it, it can be very clear that something is wrong.

True, the noise from your boiler varies depending on the source; however, this description is especially useful for repair engineers. This article highlights why your boiler is making noise and how you can fix it.

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What kind of fuel does your boiler use?

If your boiler is banging loudly, it is because of debris on the heat exchanger or a faulty thermostat. Regardless of the case, you will need to hire the services of a certified engineer to do a power flush. Other causes of boiler noise include trapped water or air, which you can fix yourself.

Most boiler issues can be sorted quickly if there is a plan to deal with them. However, to diagnose why a boiler makes unnatural noise, we first need to look at the reasons.

Our Expert Gas Safe Engineer Says:

If your boiler is making strange noise, you must never try to get inside the boiler yourself. This could be much worse than just getting it sorted quickly and easily by someone who is qualified like myself

James Murfin

Gas Safe Registered Heating Eningeer

Reasons a Boiler Might Be Making Strange Noises

Limescale air vent blockage

This type of blockage happens when limescale build-up inside the boiler is so much that it blocks the air vents. It can even inhibit the heat exchanger from functioning optimally. The blockage causes the boiler to overheat before it shuts down. In this instance, you will need to check the temperature gauge to ensure that the boiler isn’t getting too hot.

The thermostat isn’t properly functioning.

master holds a thermostat from an electric boiler in his hand

If the noisy boiler has a faulty thermostat, it is unlikely to provide sufficient heat in the system to work efficiently.

The water tank’s level might also drop or rise excessively. When the temperature goes above 100 degrees Celsius, it results in excess pressure, which, in turn, causes the water in the tank to expand. All of this results in the water hitting the sides of the tank.

This noise can be quite concerning since it is sufficiently loud to resonate through the home. It is a problem that needs to be solved as quickly as possible. Not fixing this issue as quickly as possible could cause the boiler’s internal components to become damaged, requiring replacement.

Pipes causing a loud banging sound in the boiler

The sound emanating from your boiler might be deceiving, as the issue could be from your copper pipes. You will need to investigate this thoroughly to get to the root cause. You can use the steps below for your investigation:

  1. First, find the source of the noise.
  2. Run an analysis based on the type of noise.
  3. Fix the root cause.
  4. To do this, look at your boiler and the pipes that carry water to and from the boiler space.
  5. If you hear the sound of rushing water, for instance, then it could be that a pipe has overflowed.

First, find the source of the boiler noise.

This step is all about tracking down where the noise is coming from. To do this, you will need to get a wider picture of the problems first. Identify where the noise is coming from.

It could be that your boiler is making the noise, or it could be that the noise has another originating source, such as the central heating pipe, gas valves or radiator, and is only reverberating in and around the boiler. Generally, at this point, the sounds you hear will become more pronounced, so you will need to listen to them to find out what the problem is

For example, if your boiler is creaking, it could simply be due to a flow temperature change in the pipes. Such a sound is perfectly normal for pipes and occurs frequently, so you should pay closer attention to unusual sounds.

As soon as you have identified the source of the noise, you will have a better chance of diagnosing the issue. The next step deals with understanding your boiler’s type of sound.

Run an analysis based on the type of noise.

Generally, quickly diagnosing and taking action with unusual noises can help you fix the issue, minimising the potential cost and complexity. Handling this issue quickly might even mean not requiring a new boiler. This step deals with providing a stress-free method of avoiding replacement boiler costs.

If, for whatever reason, you cannot diagnose the issue at hand, you should always enlist the services of a licensed engineer to handle the issue.

Fix the root cause of the noises

In most instances, a banging noise coming from the boiler will require professional attention. Nevertheless, there are some noises that you can theoretically fix yourself. This section will highlight those noises and how you can fix them and those noises that require professional assistance.

For future purposes, you should consider covering your plumbing and boiler to help you get faster repair services, lower costs and peace of mind to know that you are covered at all times. This way, you never have to be too concerned about where the noise is coming from. You can simply get on the phone with a qualified boiler repair engineer in no time.

Different Boiler Noises and are they Dangerous?

Before you get to the point of calling a professional, you can take basic steps to determine the cause of the noise. You first need to ascertain the type of noise.

Boiler making noise when not in use

If your boiler is making noise when not in use then this can depend on the type of boiler you have. If you have a combi boiler for instance, and you have just used it, there can be a pump overrun. This pump overrun is basically the boiler cooling itself down after use. It should be no louder than when the boiler is in actual use.

If you have a system boiler or conventional boiler, these will often start up to maintain the heat in the hot water cylinder. This happens throughout the day depending on how quickly the hot water tank cools down. To lower the amount of times a system boiler or conventional boiler has to heat up the hot water in the tank, you can make sure that it is really well insulated to keep the heat in.

Boiler Kettling or whistling noise

Boiler kettling is the term for this noise, which resembles a kettle whistling. A buildup of limescale near or on a boiler’s parts, like the heat exchange, is a typical reason for kettling. Hard water locations are where this frequently occurs.

Illustration of a noisy water heater

Some locations in the UK have hard water. The word refers to water that contains significant amounts of minerals like calcium and magnesium. Although having more of the aforementioned minerals does not necessarily make hard water superior than soft water, it does mean that it is harder.

It is believed that certain regions of the country, like Bristol, Southampton, and London, have a higher concentration of hard water. Calcium is the main cause of hard water. Calcium causes limescale to build up in layers, which restricts the flow of water. It’s unfortunate that any boiler might develop limescale buildup.

This causes water to become trapped within the heat exchanger, causing it to overheat. During the overheating process, steam is produced, causing the heat exchanger to expand. This process results in the whistling or kettling noise you hear from your boiler. Bolling air is forced through small gaps within the boiler system in the same way that a boiling kettle forces air through the spout.

However, there are a few other factors to consider when this occurs. This could be caused by a buildup of sludge and debris around the heat exchanger. The whistling sound could also indicate that your boiler pump has become clogged and needs to be replaced.

Kettling can lower the efficiency of your boiler as it damages it every time it occurs. After kettling, you will need more fuel to get to your desired temperature. This added fuel can result in higher monthly energy costs. Moreover, it can reduce your boiler’s lifespan.

Boiler making buzzing noise

When your boiler starts to buzz, it could be signalling an issue with some of the main components like a malfunctioning burner, a deteriorating pump, or faulty fans. Such buzzing sounds often arise when these essential parts become damaged or wear out over time.

The durability of boiler components is noteworthy, as they are designed to withstand substantial wear. However, the continuous operation of heating water over many years inevitably leads to wear and tear.

If your boiler is making a buzzing noise, it’s essential to act promptly. This situation warrants professional intervention. Early diagnosis and repair by a qualified Gas Safe engineer is key to resolving the problem efficiently and safely. Only an expert can accurately identify and fix the underlying cause of the buzzing.

Boiler making loud noise and vibrating

If your boiler is vibrating loudly and making a noise, it can be cause for concern. A noisy boiler that is vibrating loudly can often be associated with a potential blockage in the flue, frozen condensate pipe or fan.

This blockage if it is in relation to the flue can mean that the loud vibrating boiler noise is quite dangerous to your health due to the fact that the flue is where all the waste gasses leave your house safely.

Check the flue outside and if there appears to be something blocking, then make sure you remove this.

If the vibrating noise is to do with a frozen condensate pipe then you simply need to defrost the pipe with warm water. This is a simple and effective way, especially when temperatures are subzero.

Boiler Making Gurgling noise

When air is trapped in the boiler system, it could lead to the gurgling and bubbling noise you hear in the radiators. The gurgling noise could also be from a frozen pipe or low water pressure. You should note that gurgling noise is quite common in boilers, as a tiny amount of air can get into the heating system.

Nevertheless, it is imperative to investigate further if the noise becomes constant or increasingly louder. When it comes to this type of noise, there are a couple of basic fixes that you can carry out by yourself.

Boiler Making Loud banging noise

As highlighted earlier, a loud banging noise is typically the result of debris build-up, limescale build-up or a faulty thermostat. These issues will no doubt require the services of a professional to fix. Irrespective of the issue, the first thing to do is turn the boiler off as quickly as possible.

It doesn’t matter what caused the loud banging noise; it is undoubtedly harmful to your boiler system. Shutting the system down is the most effective thing you can do at the moment.

Call a professional to inspect the boiler as quickly as possible to rapidly eliminate the source of the noise and assess the boiler component for replacement or repair.

Other Variables to Consider Why Your Boiler is Making Noise

To have a clear idea of why a boiler makes noise, we need to highlight a couple of other variables as to why your boiler is making noise when in use.

The boiler’s water temperature is too high.

Boilers run at optimal temperature, and if the setting goes higher than recommended, it could cause severe damage to the boiler. Raising the temperature of your boiler too high could result in steam bubbles or a faulty boiler timer keeping an old boiler on may cause overheating. Most times, homeowners wrongly interpret the banging noises as originating from the boiler.

However, if, for some reason, the air has entered your pipes, you can get fluctuations in pressure which can lead to loud banging or gurgling noises. With a closer inspection, you should have no problem identifying the offending radiator or pipe.

Air can get into your boiler system in various ways: from parts that previously had issues to defective parts. Air getting into the boiler is commonplace in boilers that feed to radiators. The most effective solution is to drain the air from the boiler system. Doing this equalises the pressure. You can handle this yourself if you know what you are doing or are technical enough. Alternatively, you could enlist the services of a professional to handle it.

The water flow or water pressure is low.

When the water flow or water pressure is too low, the flow over the heat exchanger isn’t as quick as it should be, possibly due to a faulty diverter valve. This reduced speed means that the water overheats, resulting in steam bubbles that quickly expand and erupt once they come into contact with cooler water.

When to Call an Engineer for a Noisy Boiler

technician checking the heating system in the boiler room with tablet in hand

If your boiler is making a loud banging noise, limescale buildup or a malfunctioning thermostat may be to blame. To manage a system flush or a new thermostat, whichever is needed, you must call an engineer.

Because whenever your boiler makes a low banging or loud noise, the temperature settings need to be lowered since they are set too high.

Unless you have air in your boiler’s pipe system, the pipes may be banging, and the only method to fix this problem is to bleed the system.

If your boiler is making noise and doesn’t provide enough water, there may be a leak somewhere in the system. This is a fix that you can do yourself or hire a professional to do for you.

If the boiler is making a whistling sound, chances are you have a build-up of limescale. You will need to call an engineer out to flush the entire system. The system flush helps to get rid of any limescale and debris build-up.

Noisy Boiler – Conclusion

If you’ve ever wondered how to fix a boiler making noise, you will be pleased to know the steps we mentioned can help ensure your boiler works effectively, without making any unnatural noises.

Written by
James Elston
James Elston Director Of Boiler Central
Posted on: 6th February 2024

James Elston is our resident boiler and heating expert here at Boiler Central. With over 20 years in the boiler installation industry, James ensures that he knows everything there is about our Gas Safe boiler installations, energy saving and home heating solutioons. This can be from simply procuring the latest new boilers, to reviewing ensuring that Boiler Central maintains the highest standards across the workforce from office to your home.

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