Have Glow-worm Combi 30ci plus. Had the (cracked) expansion vessel replaced after leaking. Boiler pressure now rises from 1 bar to about 2.5 bar each time heating/hot water used. Have to release pressure using valve (into a bowl under boiler, very messy) Won't go down of own accord. Is it the heat exchanger that's faulty? How much to replace/fix?

Peter McGowan, October 2007

the expansion vessel is split in two inside with a diaphram! it is pressurised on the dr side with air to balance the pressure in the sealed hot water system, if it is not filled with air you will get that problem, also the boiler will automatically discharge the pressure out the pressure release at 3 bar!

toby, April 2008