18-29-911 Deliberately omitted.

18-29-912 Combination Drain and Vent System.

18-29-912.1 Type of fixtures.

   A combination drain and vent system shall not serve fixtures other than floor drains receiving only clear water wastes. Appurtenances receiving large quantities or surges of water shall not be discharged to a combination waste and vent.

18-29-912.2 Waste piping and trap.

   The waste piping and trap in a combination waste and an end vented (both ends) system shall be a minimum of 4 inch (100 mm) diameter. The waste piping and trap shall be at least two pipe increments larger than the pipe size required and at least two pipe increments larger than any fixture/appurtenance discharge tailpiece.

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.