I am fitting a secondary return for DHW in my 4 bed semi-detached house because the cylinder is in the attic. I know I can run the return in microbore - but I have left over 3/4" (22mm) fittings and pipe and was just going to use that instead. Is there any major problem with this? I guess I might lose a bit more heat to the walls, but apart from that?
Niall