I have a 4" soil pipe (cast iron). It starts from toilet, goes down to basement. Connected to the soil pipe is a 2" drain pipe (steel) from the kitchen. The connection where the 2" drain pipe meets the 4" soil pipe is broken. Tried removing broken and rusted thread pieces but will not come out without damaging 4" soil pipe. What would be a solution to reconnecting the 2" drain pipe to the 4" soil pipe? All the piping is between ceiling and 2nd floor.