Boiler making noise? What they mean

Boiler making noise? What they mean
Boilers emit noises for various reasons. A faulty boiler can be highly annoying and even dangerous. The first and foremost thing to do is identify the cause of the noise and find a remedy to fix the issue as soon as possible.

This guide will help you understand the various types of noises that occur in boilers, the reasons for them, and the solutions.

 

Types of boiler noise:

Whistling or kettling:

Wondering if your boiler could be compared to a kettle? The build-up of limescale on the boiler's heat exchanger tends to be the most common cause of boiler kettling. Limescale deposits accumulate when calcium deposits are present, they are insoluble and restrict water flow. The water in the boiler's heat exchanger can get trapped by the deposits, and the boiler may overheat, create steam, and expand. This results in a whistling sound.

There can also be kettling in boilers if sludge or debris collects around the heat exchanger or if the pump has become stuck or needs to be replaced. Kettling could cause long-term damage, and the efficiency of the boiler is reduced. You may see a rise in your monthly bills if the boiler has to use more fuel to reach its desired temperature. The overwork of your boiler can also shorten its lifespan, so you may have to replace it early.


Banging noises

Banging or popping noises from a boiler indicate a faulty thermostat or debris build-up in the boiler's heat exchanger. Deposits of minerals or sludge accumulation in heat exchangers cause kettling. This accumulation is more common in hard water areas or older cast-iron heat exchangers. A slow flow of water through the heat exchanger or any blockage which can cause the boiling of water or steaming leads to the start of kettling. In kettling, the popping up of air bubbles creates such a loud and intimidating banging noise. However, you can be sure that kettling will not cause your boiler to explode! Despite this, you need to call a gas safe registered engineer to inspect your boiler as the accumulation of debris isn't a simple DIY fix.



Aeroplane noise

Boiler making a noise like an aeroplane can be caused by multiple reasons, such as a mechanical pump failure or air and debris caught in the boiler's impeller. A single affected part of your boiler system can quickly spread to other areas and worsen your home's condition. Contact a gas safe registered engineer to identify the problem and possibly replace the faulty pump. It may be recommended to replace your boiler instead of repairing it if there is major damage to the internal system caused by mechanical failure.


Gurgling sounds

Gurgling noises in your radiators or pipework usually occur due to trapped air in your boiler system. Other reasons include a frozen condensate pipe or low water pressure. However, there shouldn't be air inside the boiler at all. If the sound becomes loud or constant, it should be investigated further. Depending on the issue, you can perform simple fixes at home yourself.


Tapping noises

Overheating causes your pipes to bang when you turn on the tap. Kettling is also a reason for this, as it builds up limescale or corrosion debris on the heat exchanger surfaces. This build-up restricts the water flow, causing localised boiling of water, turning hot water into steam. Usually, the frequent sludge formation in the radiators or pipes causes issues like slowed down water flow and blockage in the central heating system. Reaching out to an engineer is highly advised if you hear consistent tapping noises, as you cannot fix this by yourself.


Vibrating sounds:

Generally, vibrating noises in the boiler occur due to various factors—to specify, a malfunctioning pump or its incorrect setting. Accumulation of sludge in the boilers can also cause this. Excess sludge leads to boiler overheating, causing the boiler to create a vibrating noise, which is very dangerous. Therefore, a Gas Safe registered heating engineer will need to diagnose the problem to get it repaired.


Reasons why boilers make noise:

  • Low Water Pressure & Flow Rate 

Unexpected sudden falls or increases in water pressure may be a major reason for a noisy boiler causing banging and clanging in pipes.

  • Boiler Pump Airlock

You may hear your boiler banging if you have an airlock in your heating pump, as the central heating system is prone to airlocks. You will hear the sound a few minutes after turning on the boiler or the hot water.


The build-up of limescale or faulty heat exchangers

Hard water persistent areas are prone to limescale and sludge accumulation in pipes, connections to the boiler, and even the heat exchanger. Limescale and sludge formation will also damage the boiler. Banging and clanging noises in boilers are very common, yet whistling and kettling occur when the water boils, leading to the steam bubbles popping. Based on the severity of the issue, steam bubbles will create kettling, tapping, banging, and clanging sounds. The heat exchanger or even the boiler itself may need to be replaced due to this serious issue.


Sludge build-up in central heating

The sludge build-up in central heating systems is a common issue in boilers. When the interiors of boilers, radiators, and pipework break down into heating sludge, it sticks onto various boiler parts and starts flowing through the system. This is the major reason you start hearing tapping, trickling and clicking noises.


To fix this issue, flush the sludge from the heating system. Flushing off sludge is much easier than clearing limescale- for older systems that might be leaky, use a hot flush to remove sludge; for new systems, go for a strong and powerful flush. A boiler filter needs to be fitted to catch the sludge, and this filter needs to be cleaned by your boiler engineer at each service.


Failed Ignition

The day will not be good when you wake up to a much colder home than usual or jump into a cold shower without checking first to see if it's warm. Your boiler is flashing red at you. You check the error code, and it turns out there's an issue with the ignition system. Why is that?


You may have a faulty ignition lead or electrode if you hear a clicking sound when trying to ignite your boiler. This part provides the spark that ignites the boiler. Ideally, this should be examined by a trained engineer.


Components of a boiler pump failed

A boiler's pump is the most susceptible to failure because it performs many mechanical tasks. For example, a loud vibrating noise indicates that some parts of the boiler are seized. Therefore, you should get the repairs done ASAP. In addition, the boiler pump should be appropriately lubricated and corrosion-free by performing regular maintenance.


Noisy pipes

If you turn on a hot tap, you might hear your pipes making noise. This could be caused by overheating. You can check your boiler's thermostat by turning off the boiler and allowing it to cool. Then, try restarting the boiler and turning up the thermostat. Banging pipes may be caused by pipework not being appropriately secured under the floor; if you've always heard rattling noises, this may be the cause. As water runs through them, they might rattle around. 


All of these circumstances will result in the following types of noises.

Here are a few of the best ways to quiet a noisy boiler:

  • If trapped air in the system causes the gurgling, you could bleed the radiators to release it, as the very presence of it in the system could cause further problems. Therefore, it's best to get away with it as soon as possible. 

  • Ensure there is no low water pressure causing the gurgling noise by checking the boiler's pressure gauge. Check your user manual for specific recommendations, but a reading below 1 bar typically indicates low pressure. 

  • Inspect the heat exchanger for limescale accumulation.

  • Check if your boiler pump is seized.

  • The ignition leads and probe needs to be tested for any faults.



A boiler is essential for keeping our homes warm. Unfortunately, they only draw our attention when they fail. A broken boiler may not be cheap or easy to fix, but it should be repaired as soon as possible when it breaks down.


Your boiler repair costs won't be dictated by the worst-case scenario when you have boiler insurance. The Smart Cover boiler policy covers unexpected boiler breakdowns such as whenever boilers make noises and have faulty parts and controls. In addition, our boiler insurance policy will provide you with a peace of mind solution to boiler problems.