Why am I losing pressure?

does the pressure increase to around 3 bar when the heating is on? if so it may be a faulty expansion vessel.

the easiest way to tell if you have a leak on the system is to set the system pressure to 1.5 or 2 bar before going to bed and turning off the flow and return isolation valves.
when you get up in the morning if the pressure has dropped then the leak is on the boiler. if pressure is ok then open the isolation valves again and if the pressure drops the leak is somewhere on the system i.e a radiator or the pipework.

Ian
December 2009