How to Diagnose Noisy Boiler


Is your boiler making noises? Whether it’s loud banging sounds or vibrating noises you’re hearing, you’ll want to know why.

Furthermore, you’ll probably be looking for information about whether noisy boiler sounds are a cause for concern.

Boilers work hard to keep hot water and heat running around our homes, so it’s important to remember that a boiler can make a noise on startup.

In this helpful guide, we’ll help troubleshoot some common noises by showing you why your boiler might be making certain sounds.

We’ll tell you how to make simple checks to diagnose a common problem yourself and help to fix any minor boiler issues.

Common Noises from Boilers

While some noises are typical and harmless, other loud sounds might indicate a more serious problem which will need to be fixed as soon as possible.

Persistent noises from your boiler can become irritating over time. Reasons for boiler noises range from low water pressure, boiler pump, boiler fan, and an incorrectly set up boiler due to lack of maintenance.

Let’s break down these common boiler sounds.

We’ll examine which boiler noises require further investigation and those you can solve with a little effort.


Humming is a common boiler noise and there are a couple of reasons for it, both of which relate to the pump.

Humming could simply be due to normal operation. After all, the pump makes a humming noise, so it’s a good idea to check this first.

The second potential reason might be that the pump is seized – or that a part on the pump has seized.

Inspect the pump if external to your boiler to see whether it is warm or hot. It should be warm. If it is very hot, it could indicate a seized pump.

You’ll need to call a qualified boiler engineer to deal with a faulty or seized pump.

Whistling or Kettling

Whistling, or ‘Kettling’ as it is also known, is a very common boiler noise.

If your boiler is sounding like a kettle boiling water, it usually means there is air trapped inside the heating system. One way to remove the air is by bleeding your radiators. This can be done easily yourself and it’s a tried and tested method for releasing trapped air from the system itself. 

Another common cause of boiler kettling is the build-up of scale, sediment or sludge. ‘Hard water’ is the term used to describe water that possesses a high mineral content.

The build-up of limescale relates to the amount of calcium in the water. When limescale builds up, it restricts the flow of water. Over time, this can cause water to become trapped around the boiler’s heat exchanger. This can make the boiler overheat, and a kettling sound will be heard. 

Other causes of kettling include a stuck pump and a build-up of debris or sludge collecting around the heat exchanger. Both of these problems can have a serious impact on the efficiency of your boiler.

In fact, your boiler will need to work harder to get your heating and water up to temperature – which can push up the cost of your bills.

You can treat sludge by introducing an inhibitor into your boiler and central heating system to break down the collected sludge. You might also want to fit a magnetic filter (Magnaclean) to catch any debris travelling around the system.

If you have released trapped air from the system and are still concerned your boiler is kettling, call a qualified engineer who will be able to thoroughly inspect your boiler.


Vibrating sounds in your boiler are typically due to the casing coming loose.

If your boiler is making a loud vibrating noise, check the casing around it. You can easily tighten it yourself with a screwdriver.

If the vibrating noises don’t stop, call a certified engineer who will be able to help diagnose the cause.

Never remove a boiler casing, only a Gas Safe registered engineer can do this by law.


Gurgling sounds could be a few different issues.

The first, and the most easily fixable, is a radiator bleed. Leaving trapped air in the system could lead to bigger problems, so it’s best to correct the issue swiftly.

Thankfully, it’s not a big deal as bleeding a radiator system is an easy task.

In the winter months, the condensate pipe can freeze. You’ll usually find the condensate outside the house. Look for the white overflow pipe and gently tip over some warm water to thaw it.

Use warm water, never boiling. The freezing of condense pipes may leave your boiler inoperable with a fault code on your boiler.

Finally, it’s worth inspecting your boiler’s water pressure to ensure it’s giving the correct reading. Low pressure can cause your pipes to gurgle.

Use your boiler’s manual to determine the precise reading, but as a general rule, if the reading is below 1 you’ll need to increase the pressure.

Loud Banging 

You might hear your boiler banging when it’s turned on for heating, or when the hot water’s running. This could be down to an ignition issue on the boiler – call a Gas Safe registered engineer straight away.

The system or boiler pump may have failed causing all the heat in the boiler unable to be dispersed to the system giving a loud banging noise – call a Gas Safe registered engineer to inspect further.


Clicking usually means ignition failure. Check your boiler is firing up properly. If it isn’t the chances are the noises, you’re hearing are your boiler trying, and failing to ignite.


Central heating pipes can often be noisy. If yours are making tapping sounds while switched on or off, this could be well due to the expansion of the system due to heating and cooling of the metals.

This issue may require an expert engineer to investigate the problem and give advice.

How To Keep Your Boiler Quiet

While some of the noisy boiler sounds aren’t preventable, there are some simple measures you can take to ensure your boiler works as well as it’s designed to.

Good boiler maintenance can be the difference between proactively preventing a problem or catching it early.

Here are some quick and simple checks you can make:

  1. Regularly check your boiler: Check for leaks, and inspect pipes for cracks and damage.
  2. Fit a filter to catch sludge or debris: Ask your qualified boiler engineer to clean the filter during every service.
  3. Regularly check your boiler’s pressure.

Boiler Still Making Noises?

If your boiler noises persist and you’re unable to identify the underlying cause, we recommend getting in touch with Blue Emergency Cover.

Old boilers or boilers that are out of warranty can make all sorts of sounds. While not necessarily a cause for concern, long term damage can occur without inspection.

Old boilers can break down frequently, and every now and then they need replacing.

Blue Emergency Cover is on hand to fix and service boilers. We are the boiler experts and as specialists, we can help.

If your boiler breaks down, we can get you up and running again. We aim to get your boiler working with heating and hot water running around your home as soon as possible.

We offer unlimited repairs to Blue Emergency Cover plan customers.

If you need affordable boiler cover, our plans offer immediate protection, which can help avoid any unexpected repair costs. Why not speak to one of our experts today?