That is an air vent for a bathroom I'm guessing. Try a "Y" with the out pointing up and you will not need to worry about water or anything getting into the line you are installing.
Zandor Reviewed by Zandor on . attic sewer vent for smell? Hi , I am planing on building a cabinet up in my attic. There is a 3 inch PVC vent stack up there that goes right up to the roof. My plan was to "T" into that and blow my exhaust out. What do you guys think. What about when it rains? where does the rain water go? Thanks any input. Rating: 5