3280.611—Vents and venting.
(a) General.
Each plumbing fixture trap shall be protected against siphonage and back pressure, and air circulation shall be ensured throughout all parts of the drainage system by means of vents installed in accordance with the requirements of this section and as otherwise required by this standard.
(b) Materials—
(1) Pipe.
Vent piping shall be standard weight steel, wrought iron, brass, copper tube DWV, listed plastic, cast iron or other approved or listed materials.
(2) Fittings.
Appropriate fittings shall be used for all changes in direction or size and where pipes are joined. The material and design of vent fittings shall conform to the type of piping used.
(i)
Fittings for screw pipe shall be cast iron, malleable iron, plastic, or brass, with standard pipe threads.
(v)
Listed rectangular tubing may be used for vent piping only providing it has an open cross section at least equal to the circular vent pipe required. Listed transition fittings shall be used.
(c) Size of vent piping—
(1) Main vent.
The drain piping for each toilet shall be vented by a 1 1/2 inch minimum diameter vent or rectangular vent of venting cross section equivalent to or greater than the venting cross section of a 1 1/2 inch diameter vent, connected to the toilet drain by one of the following methods:
(i)
A 1 1/2 inch diameter (min.) individual vent pipe or equivalent directly connected to the toilet drain within the distance allowed in § 3280.611(c)(5), for 3-inch trap arms undiminished in size through the roof,
(ii)
A 1 1/2 inch diameter (min.) continuous vent or equivalent, indirectly connected to the toilet drain piping within the distance allowed in § 3280.611(c)(5) for 3 inch trap arms through a 2-inch wet vented drain that carries the waste of not more than one fixture, or,
(iii)
Two or more vented drains when at least one is wet-vented, or 2-inch diameter (minimum), and each drain is separately connected to the toilet drain. At least one of the drains shall connect within the distance allowed in § 3280.611(c)(5) for 3-inch trap arms.
(2) Vent pipe areas.
Each individually vented fixture with a 1 1/2 inch or smaller trap shall be provided with a vent pipe equivalent in area to a 1 1/4 inch nominal pipe size. The main vent, toilet vent and relief vent, and the continuous vent of wet-vented systems shall have an area equivalent to 1 1/2 inch nominal pipe size.
(3) Common vent.
When two fixture traps located within the distance allowed from their vent have their trap arms connected separately at the same level into an approved double fitting, an individual vent pipe may serve as a common vent without any increase in size.
(4) Intersecting vents.
Where two or more vent pipes are joined together, no increase in size shall be required; however, the largest vent pipe shall extend full size through the roof.
| Size of fixture drain (inches) | Distance trap to vent |
|---|---|
| 11/4 | 4 ft. 6 in. |
| 11/2 | 4 ft 6 in. |
| 2 | 5 ft. |
| 3 | 6 ft. |
(d) Anti-siphon trap vent.
An anti-siphon trap vent may be used as a secondary vent system for plumbing fixtures protected by traps not larger than 1 1/2 inches, when installed in accordance with the manufacturers' recommendations and the following conditions:
(1)
Not more than two fixtures individually protected by the device shall be drained by a common 1 1/2 inch drain.
(2)
Minimum drain size for three or more fixtures individually protected by the device shall be 2 inches.
(3)
A primary vent stack must be installed to vent the toilet drain at the point of heaviest drainage fixture unit loading.
(4)
The device shall be installed in a location that permits a free flow of air and shall be accessible for inspection, maintenance, and replacement and the sealing function shall be at least 6 inches above the top of the trap arm.
(iv)
Sealing disc shall be neoprene, conforming to CISPI-HSN-85, the Specification for Neoprene Rubber Gaskets for HUB and Spigot Cast Iron Soil Pipe and Fittings, and ASTM C 564-88, Standard Specification for Rubber Gaskets for Case Iron Soil Pipe and Fittings, or, Silicone Rubber, Low and High Temperature and Tear Resistant, Conforming to Rubber, Silicone, FS ZZ-R-765B-1970, With 1971 Amendment 1; and Liners, Case, and Sheet, Overwrap; Water-Vapor Proof or Waterproof, Flexible, MIL-L-10547E-1975.
(e) Grade and connections—
(1) Horizontal vents.
Each vent shall extend vertically from its fixture “T” or point of connection with the waste piping to a point not less than 6 inches above the extreme flood level of the fixture it is venting before offsetting horizontally or being connected with any other vent pipe. Vents for horizontal drains shall connect above the centerline of the drain piping ahead (downstream) of the trap. Where required by structural conditions, vent piping may offset below the rim of the fixture at the maximum angle or height possible.
(f) Vent terminal—
(1) Roof extension.
Each vent pipe shall extend through its flashing and terminate vertically, undiminished in size, not less than 2 inches above the roof. Vent openings shall not be less than 3 feet away from any motor-driven air intake that opens into habitable areas.
(2) Flashing.
The opening around each vent pipe shall be made watertight by an adequate flashing or flashing material.
(g) Vent caps.
Vent caps, if provided, shall be of the removable type (without removing the flashing from the roof). When vent caps are used for roof space ventilation and the caps are identical to vent caps used for the plumbing system, plumbing system caps shall be identified with permanent markings.
[40 FR 58752, Dec. 18, 1975, as amended at 42 FR 961, Jan. 4, 1977. Redesignated at 44 FR 20679, Apr. 6, 1979, as amended at 58 FR 55015, Oct. 25, 1993]