I am moving a wall on my 2nd floor. The vent for my 1st floor sink and bathtub were running in that wall and tying into my main stack. I plan on running a separate vent up through my roof solely to vent those 2 fixtures. My question is can I leave the vent going vertically, 90 into the ceiling joist for 1 2 foot run, 90 again turning @ 3 feet towards the wall (now forming a 5-6 feet "L" shape) and 90 again up through the roof to vent. Could this potentially cause Vapor Lock?

90s in a vent aren't an issue but don't use them in wet apps. Can you post a picture or drawing? You plan sounds Ok but hard to picture in my mind.

Sorry, new here. Not sure how to post pictures. Looking down from roof Pipe will come up (vertically), 90 right (horizontally say east), 90 left (horizontally say North) and 90 back up vertically out through roof.

Thanks for the quick response :)

If this will be a dry vent you may use as many 90's as you wish just as long as you maintain 1/4 inch to the foot slope from the roof on back. Good luck, Tom