Water has been discharging via overflow to outside. I have changed the PRV but it is still losing pressure. It drops from 1.5 to 0.6 in 2 hours. There is no air in the rads and the air valve on the pump is open. Cannot find any internal leaks.
Can you advise what to do next?

Barry Abel, December 2006

Very simple solution - solved it myself by gently bending the pipe leading to the expansion bottle. A build up of silt blocked the expansion bottle.

Barry Abel, November 2007

sounds like your expansion tank is bust (it happened to mine also after 23 months). You can fit an external one and forget about the awkward one at the back of the boiler to cure it (this is shown as optional in the manual). Cost will be in the region of £125 to get it done professionally.

Marty, September 2007

have you checked all radiator pipes, not leaking under floor boards. or check your expanssion vessel may need charging up with pressure or bladder split inside, but rare for 13 months old.

hi-spec plumbing, December 2006