Our boiler pressure has gone down to 0.3 bar, we have tried turning
the blue water knob underneath (usually works), there is no sound of
rushing water like there usually is, and the net effect of turning
the
knob is zero.

We have done a bit of research and discovered that the expansion
vessel valve can be used to pump up the pressure again. With great
difficulty we got the cap off the expansion vessel and attached a
bike
pump, we gave 20 or so pumps and turned the boiler back on, but the
pressure had only shifted from 0.3 to 0.4 - we cannot seem to get it
any higher by pumping air in.


We tested the valve, and there was a sound of escaping air, so we
guess our diaphragm is not ruptured.


We don't want to do much else because we do not want to destroy our
expansion vessel or damage the boiler in any other way.


We were wondering if we've missed any other vital steps - in another
post we read that you need to depressurise the main system first, but
we have no idea how to do that. Howe much air do you need to pump in
with the bicycle pump for the expansion vessel to regain ideal
pressure?