In ,
Dave scribed:



Thanks for pointing that out (and for reminding me to look at the FAQ)
but I can't see how adding additional expansion capacity can reduce
leakage, do you mean that your old expansion vessel was faulty?

Dave

Yes, and still is as it remains in place until my new one arrives (hopefully
tomorrow).
It puzzled me too as to why it should improve although the 'leak' is still
there, so I assumed one of two things is happening. Either the perforation
in the inner airbag has been 'sealed' shut by the pressure of the
surrounding water which I assume now fills the expansion vessel where the
air would previously have been. Or, that the PRV (pressure relief valve) was
opening under pressure when water heated up and was gently dumping water
(and hence system pressure) out of the escape pipe leading to the outside.
Although I could occasionally see drips hanging off the end, I was going to
check that by attaching a polythene bag to the end of the pipe. But as the
boiler is located on the first floor, it's a bit of a clamber up to it on a
pretty long ladder. And I'm not good with heights! :-( So I just decided to
live with the minimal loss of pressure now that the spare rad is taking the
strain as a make-shift expansion vessel. Case of not looking the gift horse
in the mouth, I guess!

Nigel