drain plug soldering?

s'ok just read Andy's comment from earlier

"Taking out the centre component with the seal is a good idea. a) there is less to heat and b) it avoids melting the seal. Buying a good quality one and cleaning it well is good. Apply flux and then heat starting at the outer end of the drain c*ck brass component and moving towards the copper fitting. This reduces conduction of heat away and boiling off of all the flux."

Ta anyway

Yes.

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.