Why are my pipes banging when the boiler comes on?

The boiler is at the heart of our homes, heating our water and keeping the house warm through the cold winter months. So when there’s an issue with the boiler it can become a stressful time, especially if your pipes are banging when the boiler comes on. Your central heating system should run quietly, so if this is happening in your home, continue reading to find out the possible causes and fixes for the problem.

Possible causes for pipes banging

There are a variety of noises you can hear in the pipes when trying to heat up water or the radiators. They include clanging, banging, tapping, vibrating and even humming. There are a number of reasons why your pipes are banging when the boiler comes on. 

The potential causes for these noises include:

  • Heating too high – your thermostat could be turned up too high, leading to an overheating issue, and creating loud noises in the system.
  • Limescale build up – a build up of limescale in the system can create some noise.
  • Water hammer – this is what happens when the flow of water is suddenly reversed, like when taps are turned off.
  • Trapped air in the pipes – a common cause for noisy pipes is air trapped inside the system. There is an easy fix for this problem.
  • Metal pipes – the metal pipes in your central heating system will expand when the heating is turned up, which may cause noise.

Fixes to stop pipes banging

Any problem with your boiler or central heating system is a big concern, but there are some relatively easy fixes for some of the possible causes behind pipes banging when the boiler comes on. Regular boiler services may be able to detect these issues before they become a problem, but there are still fixes for when they happen.

Heating too high

If you believe the thermostat is turned up too high, leading to overheating in the central heating system, then the quickest way to remedy the problem is to turn the temperature down.

Pipes banging when the boiler comes on could be down to the system being too hot, so turn the switch down a little and see if this resolves the issue.

Limescale build up

A build up of limescale, also known as boiler kettling, is common in hard water areas like London or the home counties. The boiler’s heat exchanger will accumulate limescale, which will restrict the flow of water through the pipes. This causes the heat exchanger to overheat and expand, which causes loud noises in the system.

A special cleaner can be used to flush out the limescale from the system, but seeking the help of an experienced professional to undergo the work is your best chance for the problem to be resolved.

Water hammer

Water hammer is a worrying issue with pipes. It is caused by the sudden reversal of the flow of water when the taps are turned off. This can be very harmful to your pipes, so if the noise is more pronounced when turning off taps, seeking the help of a professional is the best course of action.

Trapped air in the pipes

Trapped air in piping is a common cause for pipes banging when the boiler comes on. There is a simple fix for this problem and it involves bleeding the radiators around the house.

Bleeding your radiators will release any air trapped in the system and relieve any pressure. This should not only solve the banging, but it will ensure your radiators heat up properly and efficiently in future.

If you do bleed your radiators, keep an eye on the water pressure in your boiler as it has been known to cause a loss of pressure in the system. There is a simple solution for this, though. Turn the filling loop handles underneath your boiler so they face the same way as the pipes. You should hear water flowing back through to the boiler. Once the pressure dial has reached between 1 and 1.5 bars, return the handles to their original positions.

Metal pipes

Another possible cause for noisy pipes when the boiler comes on is the metal pipes themselves. When the pipes heat up, they expand and may well make some noise. It would be best to try and inspect some of the pipes to ensure they’ve been fitted correctly and aren’t banging on floors or walls.

If you’re unsure of how to do this, contact a professional who will know exactly what to look for.

Boiler fixes at toasti

If you’re still unsure of why your pipes are banging when the boiler comes on, get in touch with our experts at Toasti. We provide boiler cover and excellent service, such as boiler installation and services. You can book an appointment with a qualified gas engineer on our website. Or contact us on 0161 527 7326, and email us at info@toasti.co.uk.