The condensate pipe on my combi boiler comes out of the wall and rests in
the hopper of a downpipe but with this rather cold weather that we have all
been having, it has tended to freeze up quite a bit.

This got me to thinking.

The basin and bath waste pipes never seem to freeze up and these are
directly into the soil pipe. I assume, rightly or wrongly that this is
because (a) the ubends are inside the house and (b) because of the gasses
inside the soil pipe come up into the waste pipes.

Working on theory (b), would it help if I take the condensate pipe from the
hopper and feed it into the bath waste pipe using a 'T' connection and
reducing plug thereby keeping the open end out of direct contact with the
outside air. I have plenty of drop on the pipe to do this, or should I lag
the pipe, though I don't think lagging is the answer.

Your thoughts as always would be most gratefully appreciated.

Kindest regards,

James