Vokera Compact combi Pressure loss

[DrAl]

This is a very similar problem to one posted under the thread "Vokera Linea 24 pressure problem" - but we didn't get to see if that problem got fixed or not -
I've got a Vokera Compact combi with an almost identical problem - slowly losing pressure (about 0.5 bar over a month), identified some small leaks in the central heating system, fixed them, all ok. Then over Xmas noticed that when the CH is on pressure drops very slowly (losing about half a bar per week) but if the CH is off pressure drops from 2 bar to zero within 2 hours. Only evidence of any water out is from the wee copper pipe to the outside of the house (overflow I guess) when i topped the boiler up to 3 bars but this stopped after pressure dropped off to 2.5. can't find any leaks from radiators or piping in spite of lots of looking and crawling about under house - any suggestions?

 

[DrAl]

Little embarassing

Luckily(!) the washing machine broke down last night and when I moved it out of it's unit I noticed that the main pipe behind the washing machine taking water from the combi boiler to the central heating system was leaking steadily through a gap into the wall cavity with the external wall.. Joint re-tightened, pressure holding, problem solved.