Question for those who know. I am re tiling a bathroom floor that is concrete. I ripped up the old floor and upon removing the toilet, I found what is probably the original metal closet flange ( THE HOUSE IS 20 YO) which had just rotted away. It crumbled as I touched it. It would seem simple just install another flange but the PVC soil pipe has its own "flange" that the clloset flange was under. What Im trying to avoid is cutting the PVC to fit another closet flange in place. Any suggestions?

I just replaced a new double bowl sink in the kitchen, I used separate 1 1/2" P-traps for each sink and joined them into the 1 1/2" drain pipe. It works great, the sink drains super fast, the problem is , the tub is on the same drain line and the water is backing up into the tub. Is this as simple as a clogged drain line that cannot handle the volume of drain water from the new sink drains. The previous set-up was the standard disposal into the tailpipe of the other sink and 1 P-trap. so, with the divider in the tailpipe, you really only get about 3/4" drain per sink, I just increased it to 1 1/2", basically doubling it. Could the extra volume be the problem?? Did I make it drain too fast?? Also, now , when the tub drains, it also drains much faster than it ever did before. It was always a very slow drain, abnormally slow. The Bathroom is being remodeled and the toilet is not installed now., I don't know if that would make any difference, just trying to give as much info as possible.