My bathroom sink drain was clogged. Since drain stop had been out, figured something fell down hole into p trap. Anyway, when I went under sink, learned P Trap piece was connected to pipe with duct tape. When tape was removed, top of pipe leading to cast iron drainpipe was corroded and crumbled in my hands. Figured I would disconnect this pipe at base and get a new matching piece to replace it. (This pipe was about one and a half feet long with a small curved bend at top that P Trap attached to.)
Problem is I can not remove this pipe from cast iron pipe going down through floor. Threading is on outside of cast iron, but this pipe is inserted into cast iron. Should I attempt to cut this pipe and couple a new pipe to it? Or do I need to get plumber to do this?