My Baxi 105e combi is showing 3 bar when the heating is running, causing it to lose water through the blow off valve, do I have a problem with the CH Pressure Differential Valve Diaphragm?

Terry Johnson, December 2007

I had exactly the same problem, it turned out to be the expansion vessel(the internal diaphram had gone) to test, put a tyre pressure guage on the vessel, it should be about 18psi ish, it is situated at the very back at the top behind the flue. remove the plastic cap (same as a car tyre) press the centre and let a bit of air out...if nothing comes out charge it and try again but if any water comes out the diaphram has gone.

A new expansion vessel was about £60 and a pig to fit, a plumber mate said it can be done fastened to the wall. I couldnt, it had to come off...
Hope its of some help.

Fletch

Mick Fletcher, December 2007

posssible secondary heat exchanger leak or expansion vessel faulty

grahame, December 2007

I would say that your pressure is way too high unless you live in a 3 storey house....why not reduce pressure to about 1.5 bar by draining water out of the system and seeing if its stable after that?

John, December 2007