My boiler was showing error 07. I changed the primary thermistor switch as described in the installation and servicing instructions. I then refilled the system to 1.5 bar (the boiler at this point switched on and was working fine), then after half an hour the pressure went down to 1 bar. I then refilled the system back up to 1.5 and left overnight. In the morning I checked again and it had gone down to zero.

Peter, August 2009

Have a look at the outside overflow....if it has been running, the pressure relief valve in the boiler needs replacing.

John, August 2009