Why is my boiler pressure too high?

A quick guide from the experts

If your boiler pressure is too high, yet your appliance still seems to be working okay, then you don’t need to worry too much. There probably isn’t anything wrong with your boiler. Consequently, you should be able to get the boiler’s water pressure down to the right level yourself.

The pressure of a boiler should stay at around one bar. However, your machine only runs at this level when your central heating is switched off and no hot water is running.

Once the boiler starts to heat up, it makes the water expand and causes the pressure gauge to raise up.

This is normal behaviour. Boilers are well equipped to deal with these jumps in pressure thanks to their built-in pressure relief valve.  That means there’s no need for concern if your boiler’s pressure gauge needle is steering towards the red areas whilst you are using your central heating and/or hot water.

The pressure gauge on your boiler should automatically drop back down to a safe level once the central heating and/or water is turned off.

What to try if your boiler pressure remains too high

If you’ve repressurised your boiler recently, you may have caused the problem. Check to make sure the valve or filling loop has not open by accident, or the valve has loosened slightly. Close it tightly to make sure it isn’t causing the issue.

You could also try bleeding your radiators. This could help to reduce the pressure in the heating system and in turn the boiler.

Bleed all of the radiators until the air is expelled and the pressure gauge has dropped back down to a safe level. This is around one bar.

If you’re still having problems trying to get your boiler pressure down, there could be an issue inside the appliance. This may be a fault with the boiler’s filling loop. Never mess with the appliance and its inner workings yourself though! Always call in a Gas Safe Registered engineer.

You don’t need to worry whilst you wait for the engineer to arrive – if the boiler is working and not making any strange noises, the appliance will be safe. The pressure relief valve will put a stop to the appliance over-pressurising.

To find out more about our boiler installation, repairs and maintenance services, call and speak to one of our Gas Safe Registered engineers today on 0800 311 8990.

Alternatively, please fill in our free no-obligation quote form below. One of our fully qualified boiler installers will reply within the hour.