: - DonJonnio

Not sure from your question if you are worried about venting or waste, but hope this helps. I am doing an almost identical project right now on a 1934 house(1 bath, 1 main waste/vent stack). I have chosen to add a second vent solely for the new bathroom, but I will tie a new section of 3" waste line into the old main waste stack. The only info that I could find warned of possibly being too far from the main vent to get the adequate air flow. The diagram shows the new venting method.