The ideal boiler pressure should be somewhere between 1 and 2 bars.
When your radiators are cold, it’s normal to see a water pressure of one bar. Anything below one bar is considered low pressure, whilst 2.75 bars and above is considered high pressure.
If your boiler has high pressure, it is best to call out an engineer to fix the issue as soon as possible.
Reducing high pressure on your boiler can be dangerous, so it is always best to let a qualified heating engineer complete this for you.