twice in the space of 2 weeks. I repressurised it tonight to 1.5 bar and just two hours later the heating has stopped and its down to zero pressure already.
When i repressurised it there seemed to be a sound of running water down the overflow pipe.Any idea what is causing this?
Thanks

David Clarkson, March 2007

likely that the valve is letting bye or the expansion vessel is flat. The red valve which normally says three bar on it (connected to the overflow pipe) can be unscrewed and cleaned. When the system is running if the pressure shoots up to 3 or above the likely cause is a flat or damaged expansion vessel.

andy, March 2007