Hi, I am about to install a toilet in an existing building without drain. It is a one story steel warehouse on slab. the location for the toilet is next to a steel support column and the slab is 2' thick and full of re-bar there. Draining down was not an option. I got the Kohler K-3554 rear discharge toilet. Now I (and my plumber) are scratching our heads about how to hook this up. I was thinking to drain horizontally through the wall (8" thick wall) and then down over the edge of the slab and connect to my new 3" drain, but I do not know what kind of flange/fitting to use. I understand there is something called a carrier, but they seem to drain straight down. I need to go straight back about 10" before turning down.

Help?