I just removed drywall to fix a drain from a bathroom sink. I found 1.5" soft lead pipe from the p-trap to a 3" hub on the cast iron stack. Can I use some kind of coupler from the lead pipe to new plastic or do I need to replace the entire length of pipe? If I need to replace, what's a good way to remove the old lead and oakum? I'd rather avoid heat because the pipe is quite close to old wooden studs. If I need to cut the studs, I will but I'd rather not.