When turning on central heating the system pressure increases to maximum. I think the pressure relief valve is not operating correctly and wish to replace this. I know the system must be drained and replacement appears straightforward, but I should appreciate advice on any problems which may exist.

james lloyd-kitchen, April 2008

if when the heating is turned on the guage rises from say 1.5 bar when cold to 3 bar plus when hot then its the expansion vessel at fault. it could be flat but more than likely its knackered.

the pressure release valve is a valve that opens up when the system pressure gets too high. its a safety device and if it allows water out the relief pipe when the system pressure gets high and not when cold then the valve is fine.

iain, April 2008