My CH system loses half a bar in pressure every week. I cannot find any leaks from Radiators or anywhere in the system. The boiler is under 12 months old as is most of the piping and rads( there are 5 older rads and piping and the system has furnox ). The pressuer cylinder has been pushed up to 2.5bar on advice ( system says max is 3 ) and no leaks apparent but pressure loss means if I go away for 2 weeks and put the system on night operation (7degs c ) then the boiler over temp switch pops out even though the pressure has only dropped to 1 bar. Anyone got any ideas where I go from here?