Can anybody advise please I have old half inch steel water pipe running through my house from the mains stop cock as far as the kitchen which is in the process of being replaced.I have fitted a brass half inch compression fitting into the old steel pipe off one of the old elbows and run new copper from the other side and the the rest is jg speedfit plastic, just wondered if I could put a similar brass fitting into the stop cock end and a small peace of copper and run all plastic, its just what sort of threaded fitting I should use to fit into the stop cock??