I had the sewage line ran to my garage from the septic tank. I really want to put a toilet in the garage as it is detached. The location I want to put the toilet is 21 feet from where the sewage connection enters. The sewage connection will be 1.5" under the bottom of the concrete slab. So If I run the 20ft section like in the drawing, the top of the pipe will be incased in the bottom of the slab by about 3/4'' at the most for about 8ft. Here we use ABS pipe. My question is if it is okay for the ABS to be partially in the concrete. Since the 90 degree elbow for the toilet will not be flush with the finished slab, I will be putting the toilet on a raised platform. I have no problem doing this as it is for a garage. Let me know if my drawing makes sense/will work. As far as code here we are allowed a 1% slope. I could even reduce the drain line to 3" if it will still work and it will also be slightly less in the concrete.