On Thu, 2 Oct 2008 22:29:23 +0100, dennis@home wrote:

You can probably get cold enough by mixing salt and crushed ice..

That mixture will hold fairly close to 0C but will be pull heat from it's
surroundings whilst doing it. It might be able to freeze a pipe provided
you can ensuer that it is getting it's heat from the pipe and water rather
than the room in general. Certainly wouldn't be as quick as a proper pipe
freezer or the butane trick (that's for use in extremis only I think).

This simple maintenace of a a CH system has popped up several times
recently. Provided the system is sealed, as in a proper sealed system or a
open vented one with bungs in the feed and expansion pipes then as no air
can get in no water(*) can get out. Just remember to only have *one*
opening at any one time.

(*) Or only minimal like a mug full so still best to have some catching
equipment and old towels about.

--
Cheers
Dave.