I have a fault on my Baxi 80 HE instant where if you open the hot water tap the boiler will light as it should and I get hot water, the issue is when you close the hot water valve the flame will extinguish but something in the boiler will run on (possibly the pump) and the only way to stop it is to open the hot water tap again and immediately close it. This fault used to be accompanied by a screaming noise, which over time has stopped. I have been told I need a new expansion vessel as the internal one is faulty (passing water). The question is, could the fault be caused by the faulty expansion vessel or is this a separate fault?
