I'm about to embark on a bathroom remodel in a 10 x 10-foot room and will need to install a new DWV system. Currently, the only vent in the bath is a 1 1/2" that extends through the roof, I think that is the vent for the sink. The main vent is through the side of the basement wall about 25 feet away. The 4" waste pipe runs directly under the room and is in the middle of it about 5 feet from each outside wall The shower, sink, toilet, and bathtub drain into this pipe. I will be running a new 10' long pipe and drain into each side of it. My question is if I use 2 "or 3" drain pipe from each trap can I get away without venting each trap individually? Also, I'm assuming that I will need to vent through the roof so where would I install the vent in the 4" line? Would this be at the beginning of the line before anything drains into it or can it be done anywhere along the line? Thanks for the advice.