Help! My Gas Boiler Pressure is High!

Sounds scary but if your gas boiler is showing signs of high pressure, it’s predominantly an easy issue to fix.

What pressure should my boiler be at when it’s running?

If you’re boiler isn’t in use/is cool, the pressure gauge should indicate a pressure of between 1 and 1.5 bars (this is the green section on the pressure gauge); this will increase as your boiler heats when it’s in use, which is normal.

The water pressure shouldn’t go above the 3.0 bar; if it does, you will notice water coming from the pressure relief valve, which is usually on an outside wall. If the water pressure is at the 3.0 bar when the heating is on, it should easily fall back down to the ‘safe’ mark once the heating is off and the boiler is cool without any trouble. Most modern boilers have been made with an inbuilt pressure release valve which is very effective at safeguarding against rises in pressure, but there are instances where the boiler is definitely holding too much pressure, which will need to be released.

How to Depressurise your Gas Boiler

Depressurising your boiler is pretty easy but if you’re unsure/not confident, you should always ask a professional to do it for you. If you’re up for giving it a go, simply follow these steps:

Bleed Your Radiators

This is the quickest and easiest way and depressurise the entire central heating system. Simply bleed all the radiators in your home until all air has been expelled and the pressure on your boiler gauge has returned to a safe level. You can also release water from the drain off valve on the central heating system instead of bleeding your radiators.

Please ensure you have some old towels or cloths handy for soaking up water and that your surfaces are protected!

Check the valve or filling loop

If you’ve recently repressurised your boiler by opening up the pressure valve, then you may have kept it open for too long or perhaps just inadvertently knocked it open. Check the valve is tightly closed and then bleed your radiators if the pressure is above normal.

I’ve Checked the Pressure Valve and Bled my Radiators but Pressure is Still High!

If you’ve carried out the above checks but are still unable to lower your gas boiler pressure, then it’s possible that your expansion vessel needs repressurising, but this is something that should be carried out by an RGII engineer. Another issue may be with the filling loop, which may also be faulty. This too, needs to be investigated by an RGII engineer.