I am adding a small utility room to my new detached garage that will contain a toilet and sink. The concrete has not been poured yet, so I am able to lay the drains before. The 4" PVC septic main is about 30 feet away downhill, and I have already dug that trench. I cut and glued the pieces for inside the garage, and then realized maybe I shouldn't have used 3". I've read some sites that say 3" only on upper floors, and some that say its fine anywhere. So that is my question, should I trash what I've done and start new with 4", OR could I used the 3" under he toilet, then convert it to 4" to run out to the main, OR am I ok to stick with the original plan and use 3" all the way. The toilet and sink are side by side in the corner closest to the septic, so they go immediately out under the wall. Also, what is the best method to connect to the septic main (rubber T, or pvc T w/ rubber coupler), and it's not meeting at an exact T or Y in the right direction, so I need to turn the drain slightly at the end, how should I do that?