my wm 28i junior keeps over pressurising?

You say the Filling loop is off, but the valves that you turn off may not be working, with both sides of the filling loop turned off, disconnect one end of the Braided steel hose, NO WATER SHOULD FLOW, even a constant dribble will cause over pressure, if you have water flow the inlet valve will need repalcing, if however the hose does not flow, it indicates that the HW Heat exchanger has failed and mains water is mixing with system water within the Heat Exchanger

www.elanar.co.uk
May 2009