I have a half bath upstairs and am changing it into a full bath. I have a 2" vent pipe for the lower bathroom (which was run in the wall i removed to fit the tub) which runs up through the middle of the room and back into the stack for ventilation. The upstairs sink runs 3 feet directly into the 4" stack with no vent. The toilet runs directly into the stack 1 1/2 feet into the stack with no vent.

Questions:

1. Do I need to add vents for the sink, toilet or tub if I use 2" pipe and have less than 5' runs? Or can I run it directly into the main.

2. Can I relocate the vent pipe with elbows to run to the wall in the floor joists up next to the main stack and back in. it wouild add 2 more 90 degrees to the vent pipe for the down stairs.

3. Can I combine the toilet and tub before I hit the stack or must they run directly into the main stack.

Hi Doc,

1. Do I need to add vents for the sink, toilet or tub if I use 2" pipe and have less than 5' runs? Or can I run it directly into the main.
Every fixture that has a trap MUST be vented,(more about that later).

2. Can I relocate the vent pipe with elbows to run to the wall in the floor joists up next to the main stack and back in. it wouild add 2 more 90 degrees to the vent pipe for the down stairs.
You may add as many elbos as you wish as long as you maintain slope and don't build a trap in the line.

3. Can I combine the toilet and tub before i hit the stack or must they run directly into the main stack.
You may combine the two only if you run a vent on the tub.

Let me show you a typical, (in my area) bathroom group rough in. This configuation only uses one vent for the entire group.
4" ,(under cement and basements) 3" (on first and second floor) from the toilet to the main. The lavatory to connect to the toilet drain line and vent to the roof or revent back in the attic to a existing roof vent. The tub/shower to connect to the lavatory drain line and be wet vented by it as will the toilet. Be advised to always check local codes before changing or remodeling your drainage system. Good Luck, Tom