pressure loss - overflow?

We have a worcester combi boiler which is losing pressure ( around 1/2 bar every 12 hours) I\\\'ve traced all the joints and can find no evidence of a leak. However the overflow is dripping constantly. Is this likely to be the problem and if so how do I fix it?

Thanks in advance

the overflow is the pressure relief valve. check the pressure of this system when the boiler is operating and see if it rises to over 3bar. if it does then the expansion vessel needs recharging or replacing.

cannot remember how to do it on this boiler so dont know if its hard to do, sure some of the other lads will know though

Thanks for that. I did the no-no and flushed the pressure relief valve (being fairly sure that the system was clean, due to it having been fully flushed about a month ago). I just gave it a quick blast through a couple of times and it now seems to be ok. Time will tell

Thanks again