Originally Posted by
Milo Dolezal
Pipe that sick up 10" from the floor is the toilet inlet. You will cut it down flash with the finished floor and install / glue a closet ring over it.
Threaded 4" pipe is your Clean Out. You don't use this pipe. You leave it the way it is with plug installed. Its purpose is to accept snake in case of sewer line blockage.
To find the buried pipe: Take a hammer and keep tapping on the floor, in various places, across the entire bathroom. You will hear/feel when the different sound comes up. That's the location of your buried pipe. Take a large hammer and hit that spot several times. Concrete will break, exposing the pipe