Originally Posted by Marlin
I really can't tell anything with those pictures. Yes the large pipe is your toilet waste. Is that a 2" pipe with expanding foam around it? If it is my guess is that is meant to be a waste for a tub so you have room to get your trip lever in.
Additionally there should be a vent for the toilet, a vent for the tub/shower, and a sink waste line.
All of that could be wet vented into the toilet vent quite easily, but i'm not sure why they have the 3" stubbed out so high... usually on concrete, you go ahead and set the flange....
I'm a little confused as to what i'm looking at as well.