I have a worcester bosch 29cdi less than 1 year old. My boiler is generally set on 1 bar. However I have tried to raise the pressure to 1.5 bar several times making sure I do it when the boiler is switched off and has cooled down. The needle does rise and it stays on the new setting until the boiler next switches on. But when it then switches off and cools down again the needle drops back to 1 bar. I have tried to increase the pressure several times to 1.5 bar , but each time this is done, and the boiler comes on and goes off the needle drops back to 1 bar. It never drops below 1 bar though so I don't think we can have a leak.