What is the correct location for the vent tie-in to the underground plumbing? We originally had underground plumbing installed in the basement for a future bathroom, but we are changing the floor plan and need to re-arrange the underground plumbing. The new layout is: a 3" PVC pipe coming off the main sewer (underground) with the toilet at the end. From the toilet end, it is first the tee for the tub drain, then the tee for the sink/vanity drain before hooking up to the main sewer. Is the vent supposed to be between the last tee and the main sewer? Does it matter where the tee is for the vent along 3" pipe?
Yes, it matters where vents are located in relation to the traps that they're venting.
Check with your Building Inspection Department for local codes, permit and inspection requirements for this plumbing work. Then you know that it will be right.