"Tony." g wrote in message ...
I have a Glow worm swift flow, the problem is when the boiler is off, the
pressure drops quite dramtically there is NO visual evidence of any leaks,
then when the boiler is switched on the pressure can in crease to as much
as 3bar, one radiator upstairs never comes on, despite being bled and water
coming out, both pipes never to radiator never get warm.

What do you think.

You expansion vessel has lost its charge, hence, when your boiler is on, the
water heats and expands, and without its expansion vessel to absorb the
expansion the pressure will rocket to 3 bar whereon the pressure relief
valve will dump water outside. When the boiler goes off the pressure gauge
will be low due to the water lost outside.

You need to recharge the expansion vessel, if it is split you need a new one
(either replacing the existing one on the boiler or installing an
appropriately sized one external to the boiler.

Angus