In an earlier contribution to this discussion,
Andy Wade wrote:

Set Square wrote:

It best to pump air in with the valves shut, too - and then crack
open a valve and listen to the water being expelled.

But you can't start the process that way as the air's got nowhere to
go (unless you attach an external pressure vessel, which would seem a
little OTT).

In my experience, there's always *some* air in the top of a radiator, even
when bled, because the bleed screw isn't at the highest point. So you
compress this to start with, and then have more to go at once you have
expelled some of the water.

What do you use for your air supply? - Foot pump, compressor, ...?

Foot pump, operated by hand.


It usually takes several goes. You can tell when the rad is empty -
because the last slug of water/air mixture makes a very rude noise as
it passes through the valve!

I'm just wondering whether this might be a good way of disturbing the
sludge, which inevitably collects at the bottom of every radiator, and
distributing it round the system. That would certainly be a Bad
Thing.

I've never experienced any problems due to this. I think most of the sludge
stays in the rad. You certainly get some coming out when you upend the rad,
having removed it. [You still have to be careful to collect any remaining
water/sludge when undoing the unions - but it's much easier than undoing
them with the rad full of water].
--
Cheers,
Set Square
______
Please reply to newsgroup. Reply address is invalid.