Existing drains in house are all threaded. I've replaced most so far to the horizontal mains. The last one (which of course is clogged) is the sink in the master bath. This is 1 -1/4' all the way to the main, where it connects to a 1-1/2 or 2" by 1-1/4 ' bushing. it's near impossible to access this bushing as its against an outside wall and tight in the joists. my best option i believe is to dump it into a newer 1-1/2 plastic line that serves a tub and bathroom sink. (i know that's already too much). Any other ideas?