hi with the radiators on from starting point the pressure should be 1 to 1,5 bar when cold with your heating on look at the pressure gauge does it go up into 2.5 to 3.0 bar quickly then blow the water off outside via the 15m copper blow of pipe if so the problem lies with your expansion vessel if without you using your central heating the pressure is still dropping then you have a leak on your central heating pipework have you recently had a carpet fitted or banged in a protruding nails in your floorboards which could have nicked a pipe universalheatingsparesuk
byron universalheatingsparesuk, October 2010
