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.

I have a pressure assisted toilet, and recently it stopped flushing properly. Can't find much info about the Kohler model and my trobleshooting didnt help much. So I decided to convert to regular flush, and I installed the traditional water fill valve, flapper etc. The toilet does not flush at all. Is it possiible to convert to a normal flush, or is there some mechanical difference in the bowl that prevents conversion ? Is it possible there is just some type of clog ?