18-29-912.2.1 Branches.

   A branch more than 15 feet (4.57 m) in length shall be separately vented. The minimum area of any vent installed in a combination waste and vent system shall be one-half the diameter of the drain pipe served, but not less than the minimum indicated in Table 18-29-916.1.

18-29-912.2.2 Sinks, lavatories, and other fixtures.

   Sinks, lavatories and other fixtures that are roughed-in above the floor shall not be permitted on a combination waste and vent.

18-29-912.2.3 Long mains.

   Long mains shall be provided with additional relief vents located at intervals of every 100 feet (30.48 m).

18-29-912.2.4 Floor drains.

   Floor drains shall be vented at the end of the waste line or individually vented.

18-29-912.3 Size.

   The minimum size of a combination drain and vent pipe shall be in accordance with Table 18-29-912.3.

Table 18-29-912.3
Size of Combination Drain and Vent Pipe
(for Floor Drains Only)

Diameter Pipe (inches)	Maximum Number of Drainage Fixture Units
	Connecting to a horizontal branch or stack	Connecting to a building drain or building subdrain
2	3	4
2 1/2	6	26
3	12	31
4	20	50
5	160	250
6	360	575

 

For SI: 1 inch = 25.4 mm.

18-29-913 Island Fixture Venting.

18-29-913.1 Limitation.

   Island fixture venting shall not be permitted for fixtures other than sinks and lavatories. Residential kitchen sinks with a dishwasher waste connection, a food waste grinder, or both, in combination with the kitchen sink waste, shall be permitted to be vented in accordance with this section.

18-29-913.2 Vent connection.

   The island fixture vent shall connect to the fixture drain as required for an individual or common vent. The vent shall rise 6 inches (150 mm) vertically above the flood rim level of the fixture being vented before offsetting horizontally or vertically downward before connecting to the outside vent terminal.

18-29-913.3 Vent installation below the fixture flood level rim.

   The vent located below the flood level rim of the fixture being vented shall be installed as required for drainage piping in accordance with Article 7, except for sizing. The vent shall be sized in accordance with Section 18-29-916.2. The lowest point of the island fixture vent shall connect full size to the drainage system. The connection shall be to a vertical drain pipe or to the top half of a horizontal drain pipe. Clean-outs shall be provided in the island fixture vent to permit rodding of all vent piping located below the flood level rim of the fixtures. Rodding in both directions shall be permitted through a clean-out.