My boiler is 8 years old. Never been serviced. The pressure dropped last summer when I was not using the boiler, so I kept filling it up to 1.5 bar.
Just a week ago I noticed the pressure had risen to 2.5 bar. It now goes to 3.1 bar when the heating is on and never drops below 2.5 when the heating is off.
HELP!!

dianne, February 2009

It could hace one of the following problems.
1. Filling loop passing through the isolation valve try disconnecting the braided hose if the isolation valve & check
2. The expansion vessel is flat. the vessel is a flat round cylinder usually at the rear of the boiler it will have a screider valve like a car tyre. Drain the boiler attach a footpump to the valve and recharge the vessel to 0.75bar. Fill back up and test that the pressure stays at about 1.5bar on the boiler pressure gauge.

Richard, February 2009