In an earlier contribution to this discussion,
wrote:

On 7 Jan,
"Roger Mills" wrote:

Likewise when you open
the other valve, heating water should come out - so this is a good
way of making sure that the system is unpressurised before you pump
up the air in the expansion vessel.

Not true, there should be a double check valve at the boiiler inlet to
prevent the system contents from backflowing into the mains.


I stand corrected! Actually, I did wonder after I had written it whether
there was perhaps a non-return valve rather than a manual tap at the system
end. [One day I'll convert my system to pressurised, then I'll have
first-hand experience! g.]


We have a car tyre pump with gauge, but we're too scared to attach
it to the expansion vessel value, in case it over-inflates the
vessel and ruins it. Also, the gauge on the car tyre gauge goes up
to 250 psi - much more than the 7 psi needed for the expansion
vessel,

The usual charge pressure is
about 0.7 bar - which is 10psi not 7psi.


Did I say 7psi? I meant 0.7 bar, which you rightly say is 10psi (ish).


No, it was the OP who said it.
--
Cheers,
Roger
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