§ 86-209. Vents.

(a)

Generally. Fixtures located on the same floor discharging into a double Y or sanitary tee cross may be vented by a single vent pipe. Fixtures located on opposite sides of a wall or partition in the same building, or directly adjacent to each other, may have a common vent pipe. No vent shall be taken off the crown of a trap. Any back vent serving a trap shall be connected as close to the trap as possible, but in no case shall the distance be more than 24 times the inside diameter of the branch.

(b)

Grade. All vent and back vent pipes shall be free from drops or sags, and shall be so graded and connected as to drip back to the stack or branch by gravity. Whenever it becomes necessary to trap a horizontal vent pipe, it shall be drained back into a stack or branch by gravity. A loop vent may be installed as provided by the state plumbing code.

(c)

Size. Size shall be determined from the number of fixture units connected thereto, as provided by the state plumbing code. A branch pipe, to which two and not more than eight fixtures are connected, may be vented by a circuit vent, which shall be taken off ahead of the last fixture. Where fixtures discharge above a branch served by a vent, each such branch shall be provided with a relief wet or dry vent, taken off ahead of the first fixture, with a diameter of not less than one-half the size of the stack. No relief vent shall be less than 1½ inches in diameter. Vents for water closets shall be of the following sizes:

Two-inch ..... For a battery of two closets

Three-inch ..... For a battery of three to six closets

Four-inch ..... For a battery of seven or more closets

(d)

Termination. All vents shall run separately through the roof, be reconnected at least 12 inches below the roof; or be reconnected to the main vent pipe not less than 38 inches above the highest floor on which fixtures are placed. No fittings for future connections shall be placed in pipe above the point of revent connection. No vent pipe through a roof shall be less than four inches in diameter. Changes in diameter shall be made by means of a long increaser at least one foot below the roof. The roof terminals of all vent pipes shall extend at least three feet above any door, window, scuttle, air shaft or other opening used for ventilation when located at a distance less than 12 feet from such terminal.

(Code 1966, § 10.74)