Vaillant boiler issue - increase to delivery pressure from pump, this varies in operation - i thought just a problem with HWD exchange so changed but it appears tobe related to maybe divertor valve ?
I have had water depensing down relief for boiler so is it to do with diaphragm ? Can only think thats where mains water would be in contact, other than dhw exchange !

Steve, December 2010

your not making a lot of sense what is the starting pressure what does it end up at does it increase slowly or very fast when does water escape from the pressure relief valve all the time or when the boiler is on ???

brian, December 2010