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Why Is My Boiler Making a Noise?

My boiler is making a banging noise

If your boiler is making a strange banging noise you could have a build-up of sludge or limescale in your boiler’s heat exchange – causing a restriction of water which begins to overheat & steam.

Kettling causes your system to work harder and often shortens the lifespan of a boiler. This isn’t a major issue, but we would recommend getting a Gas Safe engineer to flush out the system, which will clear out the build-up of sludge & limescale and will aid in restoring the boiler efficiency.

Estimated flush cost of £300+ depending on how many radiators you have in the home.

My boiler is making a gurgling noise

Gurgling noises can be air trapped in the system or a blockage at the bottom of the boiler. The majority of the time gurgling noises are a tell-tale sign that your condensate pipe is frozen.

Your condensate pipe (or wastewater pipe) will need to be thawed to fix the issue – this an incredibly easy fix. Here's our guide on how to safely thaw a frozen pipe.

After you’ve completed our guide, all should be working as normal.

My boiler is making a whistling noise

Whistling noises can be caused by kettling, loss of water or air is trapped within your system. If it is trapped air, you can easily fix this by bleeding your radiators.

If you don’t feel comfortable bleeding your radiators, you can always call a Gas Safe engineer to sort it out. When they bleed your radiators, they’ll also find out what caused air to become trapped in the boiler and perform the appropriate repairs.

There will be a call out charge of at least £50 - £60 per hour.

Things to look out for

Water pressure

If your water pressure is too low it won’t cause any damage, but it will affect the efficiency & effectiveness of your boiler – so you’ll be paying more in energy bills.

The standard operating pressure is usually 1 – 1.5 bars of pressure. Anything above or below that will need to be repressured. 

Water flow

If you have poor water flow, the water could get stuck in the boilers heat exchanger. So, when the water starts to boil, steam & expand the boiler will make a noise like a boiling kettle, and have a slight whistle. This is very common in older boilers or central heating systems. 

Incorrectly set thermostat

If your thermostat is set too high it could cause a boiler to become very noisy. Try lowering the temperature on your thermostat, so your boiler isn't constantly running too high and working too hard. This should help your boiler stay quiet.


A build-up of limescale will cause steam bubbles to be produced, which will make a loud noise like a kettle boiling. Limescale has a significant impact on the lifespan & energy efficiency of a central heating system.

To fix the issue we'd recommend getting a gas safe engineer to administer a chemical flush or descaler to clean up the pipework and get rid of the build-up of limescale within the system.