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The length of a stack vent shall be the developed length from the highest horizontal or fixture branch connected to the stack to the terminal of the stack vent in the open air.

A vent stack or main vent shall have a diameter of at least 1/2 the diameter of the soil or waste stack, but in no case less than 1 1/2 inches, and, depending on its developed length and the number of fixture units installed on the soil or waste stack, be in accordance with the table in § 221-267 . In determining the developed length of vent pipes, the vent stacks and branches shall be considered continuous.

The diameter of a stack vent shall not be less than the diameter of the soil or waste stack.

The diameter of an individual vent shall not be less than 1 1/4 inches nor less than 1/2 the diameter of the drain to which it is connected.

The diameter of a relief vent shall not be less than 1/2 the diameter of the soil or waste branch.

The required size and length of vents for stacks and branches shall be as follows: Diameter of Pipe (inches) Maximum Number of Fixture Units Permitted Maximum Developed Length For Each Size (feet) 1 1/4 1 30 1 1/2 6* 35 2 20 60 2 1/2 40 100 3 82 150 4 250 250 5 500 300 6 1,250 400 8 2,400 Unlimited * Except six unit traps.

No water closet, siphon-jet, pedestal, pedestal urinal and blowout shall be vented with less than two-inch vent pipe.

The diameter of loop vent or circuit vent shall not be less than the diameter of the horizontal soil or waste branch or the diameter of the vent stack, whichever is the smaller.

No vent shall be required for a leader trap, a backwater trap, area drain or subsoil catch basin drain.

When excessive cutting for a vent pipe is necessary, the Plumbing Inspector may, in his discretion, permit the use of an approved antisiphon trap, but such permission shall not be construed as granting permission in any other case.

All main vents or vent stacks shall connect full size at their base to the main soil or waste pipe at or below the lowest horizontal waste branch or with the building drain. All vent pipes shall extend undiminished or increased in size above the roof or shall be reconnected with the main soil or waste vent at least three feet above the highest fixture branch. The pipe above the intersection shall be increased in accordance with the table in § 221-267 of this article. Wherever possible, the base of the vent stack shall receive the wash of the adjoining soil or waste.

Offsets in soil and waste stacks above the highest fixture connection, and offsets in vent stacks and connections of such vent stacks to a soil or waste pipe at the bottom or to the building drain, shall be made at an angle of at least 45º to the horizontal, except that where it is impractical, because of structural conditions, to provide a forty-five-degree angle, the Plumbing Inspector may permit a reduction in the angle under such condition as he may prescribe.

A branch serving any fixture on the lowest floor on the upper section of the stack shall be connected to the lower section of the soil or waste stack.

Roofs and paved areas, yards, courts and courtyards shall be drained into a storm sewer system or a combined sewer system where such systems are available.

Stormwater shall not be drained into sewers intended for sanitary sewage only.

Leaders and storm drains, when connected to a combined sewer, shall be effectively trapped, except roof leaders and conductors, where the roof or gutter opening is located not less than 12 feet from a door, window or ventilating opening. When the sanitary and stormwater drainage are combined within the building, one trap on the main storm drain of the building may serve. Traps shall be set below the frost line or on the inside of the building.

Where subsoil drains for drainage are placed under cellar floors, the seepage shall be piped to a silt pit or sand trap by field tile. The silt pit or sand trap shall discharge into a four-inch running trap with two cleanouts and, in localities where the administrative authority thinks it advisable, it shall have a backwater valve. Subsoil drains may discharge into a properly trapped area drain or sump.

Subsoil drains below the sewer level and cellar floor drains or drips from machinery shall be discharged into an independent sump or receiving tank, the contents of which shall be automatically lifted and discharged into the drainage system above the cellar through some properly trapped fixture or drain. The discharge of automatic systems shall be protected against back pressure.

When subsoil catch basins are installed below the sewer level, automatic electric ejectors provided with a ball float or equivalent shall be used. Such ejectors or any device raising subsoil water shall discharge into a water-supplied, trapped and vented sink or into a stormwater drain.