A vent must rise vertically to a point above the flood-level rim of the highest fixture served before it may offset horizontally, by at least:

Giải thích

A vent must rise to at least 6 inches above the flood-level rim of the highest fixture served before offsetting horizontally, so that any drainage backup cannot enter the horizontal vent. Offsetting at or 3 inches above the rim risks fouling the vent, and 12 inches is more than the code minimum.