my boiler keeps losing pressure and drips every so often i keep building the pressure back up, the only way that it holds pressure is when i close the overflow pipe but have to open this if i have the heating on otherwise the pressure builds up too high i have replaced the pressure release value 3 times but still drips the dripping isn't that much of a problem but its the losing pressure what could be the problem?

Tracy, May 2012

expansion vessel faulty
needs recharging or replacing

manwithnoname, May 2012

What on earth are you putting the pressure to.

Should be 1 bar COLD, SO Switch it off, LET it go cold. Several Hrs, Or overnight.
Over pressure releases at 3 bar, Should never get to that, unless a problem. You should also NOT be able to close off the overflow. IT is A SAFETY FEATURE. IF you can, Who ever installed it needs to be shot.
The system WILL loose pressure, if the safety valve is dripping. Which it will if going above 3 bar.

SD, May 2012