46 C.F.R. § 153.352
B/3 and 4 m venting system outlets
A B/3 or 4 m venting system outlet must:
(a) Discharge vertically upwards; and
(b) Prevent precipitation from entering the vent system.
A B/3 or 4 m venting system outlet must:
(a) Discharge vertically upwards; and
(b) Prevent precipitation from entering the vent system.