Hi does anyone know if it is possible to check the pressure on the expansion tank without draining the system. I am reluctant as I have just put in a rust inhibitor. If i need to put pressure in does this meen there is water in the expansion tank?

Nick, April 2009

The expansion vessel, as fitted to combi systems is actually in two halves - one tank separated by a rubber diaphragm. The boiler side is full of water, the other side is air pressurised to about 10 psi. You'll see a schraeder valve there for testing the pressure and topping up. If you press the valve, and water is present, the diaphragm has failed.

John, April 2009

expansion tank or expanssion vessell, if its a vessell look for the valve like acar tyre valve and see if theres any air in or connect a pressure reader

STE, April 2009