We have a Worcester Bosch boiler Greenstar 25Si/30si. It has been losing pressure over the last few weeks and we thought that the problem was a leaky pipe in the concrete floor even though there is no sign of water anywhere. The installer has isolated the downstairs radiators so that the system is only working upstiars, but the pressure is still dropping to 0 when the boiler is on- or off! Is there anyhting else that could cause the pressure to fall like this?

Suziepink, December 2010