I'm doing a little bit of plumbing work for a new kitchen but a little unsure about something.At the moment my water pipes to my sink are galvanized steel (most of it is).Now i want to re-route my water and fit copper pipe to the steel.My cold water pipe has this done to it already by a plumber(or DIY er)i presume.However i want to do this to the hot water pipe as well.I have got a 3/8 bsp connector with a compression fitting on the other side to do this its just a question of unscrewing a section of the steel pipe but i'm not sure if the joint will unscrew easily as the house is about 40 years old.Can i heat the pipe or would i risk cracking the pipe.