More a question out of interest, but, Are Pressure Relief Valves REALLY so unreliable once opened? I have read quite a lot about them never closing properly after been operated, either manually or by true build up of pressure. I think I may need a new one as it was operated manually, and ever since I cannot get the pressure gauge to stop dropping even when the heating is off. I just find it hard to believe they are so unreliable, given it is in their design to be operated? I would be interested to know peoples experiences with them, and average prices for replacement, its hard contacting anyone on a Sunday.
