i need to know what causes the pressure to rise continually when my central heating is on,and the pressure to drop when the hot water is taps are turned on?

paul, October 2008

Hi Mick
Thanks very much for your help,the boiler is workable with the heating control turned down to about halfway,does this support/confirm your diagnosis?

paul, October 2008

I would guess you have a leak on the inside of the plate to plate heat exchanger, mains would then get into the heating system and cause the pressure to rise but when taps opened pressure will drop down. Other thing that causes pressure to rise on heating is no air in the pressure vessel, but that wouldn't let pressure fall when hot tap opened.

Mick Andrews, October 2008