Answer: A house of that age may have copper drain pipe, but more likely it is lead and beyond the skills of the average DIYer to repair. Since this is a drain, though, I don't believe lead-free solder would be required if it is copper pipe and you did undertake the repair. Lead-tin solder is still readily available, and it is somewhat easier to work with, especially on such a large joint. You'd need something a little stronger than the standard propane torch, however. But before doing anything rash, go to a hardware store and look for some flange repair fittings. These are pieces of metal that can be worked under the edges of the existing broken flange to provide a solid mount for the toilet bolt. In any event, keep in mind that you don't need a lot of force to hold a toilet in place. The weight of the toilet does most of the work, and you just want to keep the toilet from sliding around.