Thanks Gluestick, RicandJo. So the exchanger problem of a leak internally is not the cause? I've looked at the picture and my expansion vessel is 'slimmer' than this picture. Would I need the precise replacement for my boiler, or are they all universal? Also, my current vessel, sits in a holder on the back of the boiler casing. The bricodepot one would just hang off the flexible braided pipe!