The expansion vessel has gone the boiler unfortunately. I say this because water as well as air came out when I pressed on the valve. I had hoped that the loss of circuit pressure was just due to a faulty PRV (which also needs to be replaced).

It doesn't look feasible ( for me anyway) to remove the faulty unit due to inaccessibility of the union nut and the inadequate clearance at the top of the boiler prohibiting the removal and refitting of the vessel.

So I was wondering what size of external vessel I would need (the same as the original?) and the best place to 'T' it in . I've read it goes in the CH return leg of the pipework but are there any other factors to bear in mind when fitting it? Do I have to stick with a Vaillant part if there are cheaper alternatives?

As a matter of interest how does the pipe connecting the (original) vessel fit into the rest of the boiler tubing, it looks like a push in connector held with a clip? If this is all it is could I attempt to remove it and connect the new vessel to this point?

Thanks all,