"fred" wrote in message ...
In article , John
writes
"fred" wrote in message ...
In article , John
writes

Remember that the radiator will be at pressure so you cant prevent it
from
****ing out some water by just closing the valves and the air vent.

I did wonder about that but they suggest you release pressure on any
trapped air by opening the bleed vent first and then closing it before
opening the drain screw over a drip tray and fitting a hose

Possible faff, but they are dinky.

A large radiator will need to squirt out quite a bit before its pressure
is
released.

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.
--
fred
FIVE TV's superbright logo - not the DOG's, it's ********



Perhaps the quantity isn't massive - but the pressure makes it seem a lot. I
guess there is some air above the bleed valve - and some elasticity in the
construction of the radiator. I have only just gone"pressurised" and it took
me by surprise.