I have a drain pipe from my upstairs kitchen and washing machine that is corroded. It runs above a downstairs hallway and closet. I have cut away ceiling wallboard and located a hole as well as other spots of corrosion. The region is between two fittings where other drain pipes seem to join in so there are metal joints (likely where they screw in but I cannot get a great view of these) at each end.
Should I try to locate good parts of this metal pipe and attach a new piece of pipe? If so, do I use PVC with some type of coupling (Fernco?) to attach a good piece of the metal to the pvc? Or should I use metal? What if I cannot find a good piece of the old metal pipe at each end where I can join? The house is over 40 years old so it may be hard to unscrew the old pipe. Am I best to just call a plumber now that I've located the problem area? Thanks.
You're best bet is to rebuild that line all the way back to the cast iron stack.
You cannot unscrew it either, its too old. Its not too difficult of a project. Use shielded ferncos or nohub bands to connect to the galv. pipe.