My boiler pressure is at maximum of 4 bar and water pours out of the overflow pipe. I reduced the pressure but with half an hour it has increased again.
Is there a fault with the expansion vessel?
Im waiting for an engineer visit tomorrow, can i still use the the system?

lisa, April 2008

if it increases when the boiler is off and just keeps rising then there is mains cold pressure getting into the heating system. either filling loop not closed properly or passing or holed heat exchanger

i, April 2008