Question

Hi Tom, I have a Vailliant mag boiler. It appears to be leaking out of the exchanger part. So I've changed the diaphragm and it's still coming out of the seal. Does it have a gasket here too? As I never removed one before the problem occurred....?

Answer

If the heater has suffered frost damage then it is likely that the upper body of the water control assembly has warped and as the diaphragm also forms the seal it is unlikely that you will repair using the diaphragm. You will also need the upper body, our part 117057