I'm doing some bathroom remodeling and need to move some drain lines, I have cast iron drain lines that are connected at the hubs with donuts, how do I remove the old drain pipes and donuts so I can replace them? I will probably go back with PVC pipe.

I will probably go back with PVC pipe. If you're not going to use the old cast iron pipes simply break the hub with a hammer. Another way would be to simply pry the rubber out. Let us know if we can help with your remodel. Good luck, Tom