I'm finding little information on what fittings are allowed for
dry-vents. Drains are understandably restrictive. I need to join
several dry-vents before going out the roof. Must I use Ys to connect
horizontal dry-vents or can I use sanitary Ts or straight Ts? Can I
connect a vertical dry-vent to an overhead horizontal dry-vent with a
sanitary or straight T?