On 2007-10-01 18:43:51 +0100, "Vass" said:

prob stupid Q, but if you dont know, you don't know
The drain plug I'm putting into my CH system is Brass
its 15mm diameter, can I solder to it?

Yes.

Remove the insert piece because that has at least one plastic or rubber
component.

Clean up the male part with steel wool etc. as normal. Clean up the
female parts of the tee or other fitting and apply flux before
assembling.

Heat from the brass component first to avoid that conducting away heat,
and then towards the copper tee or other fitting. Apply solder and
allow to cool. Clean up and reassemble the insert into the brass
fitting.