I am installing a bar sink in my basement. I need all the height I can get in order to hook into my main drain where it exists the house. The sink is 15" x 15". The drain pipe will be 2". A studor valve will be inserted after the trap. Question is, how far below the bottom of the sink does the insertion of the drain into the wall have to be? The drain will run horizontally once it enters the wall at the standard 1/4 inch per foot pitch.