I am new to this forum and tried a search, but due to my relative inexperience in terminology, I couldn't find what I was looking for. Forgive me in advance if this is the inappropriate location for this question.

I am in the process of converting a small bedroom into a master bath on the top floor of the house. I have a 2" dedicated drain pipe that runs up from the basement, through the downstairs wall, tees off for the new tub and shower in the floor between the floors, and continues up through the attic and roof as a vent pipe.

The tee for the tub and shower is about 6' away from the tub and shower drain locations. The shower and tub are separated by a 2x4 wall, and the drains are about 8" apart. When I connect these two drains to the dedicated drain pipe 6' away, should they each have their own pee trap, or can I merge the two just before the pee trap like a double sink? The bottom of the tub and shower are about 10" above the top of the horizontal pipe that leads to the dedicated drain pipe with vent, so unless there is a clog, is there a realistic chance of water coming up the other side during normal draining?

Good morning, I hope you're going to tell me that you have a vent from the lavatory running up through the roof or reventing, (tieing back into a outside vent) back in the attic that is venting your bathrooom group and that you're not running a toilet past fixtures that are unvented. The Standard Plumbing Code states that you can not discharge a major fixture past a unvented minor one. Also section 1602.2 (b) states that each fixture shall have its own trap. I would suggest that you go down to the Building Department for your city or county and pick up a copy of the local plumbing code. Venting is every bit as important to a plumbing system as drainage is. If you have to pull a permit on your job then you will be inspected. You will have to know these things when you lay out your job. Having said that, I wish you good luck on a difficult job. Tom