In article
,
harry writes
On 2 Oct, 01:06, fred wrote:
In article , John
writes

How so? Water is incompressible and so cannot retain any pressure.
Pressure can only be retained by any unbled air in the radiator which
can be released via the bleed valve with perhaps a trickle of water.

This is the case when both ends of the rad are turned off as described
in the instructions. Any pressure stored in the system (via the
expansion vessel could then be released by opening the rad valve to link
the system back to the rad.

There is usually a small amount of air/gas in raditors. You can't
bleed it all out.

I think, "Pressure can only be retained by any unbled air in the
radiator which can be released via the bleed valve with perhaps a
trickle of water." covered that.
--
fred
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