Drainage System Sizing.
§ 18-29-710.1 Maximum fixture unit load.
The maximum number of drainage fixture units connected to a given size of building sewer, building drain or horizontal branch of the building drain shall be determined using Table § 18-29-710A. The maximum number of drainage fixture units connected to a given size of horizontal branch or vertical soil or waste stack shall be determined using Table § 18-29-710B.
§ 18-29-710.1.1 Maximum fixture units.
The maximum number of fixture units that may be connected to a given size of house drain, horizontal branch, or vertical soil or waste stack is given in Tables § 18-29-710A and § 18-29-710B. Storm and combined house drains and house sewers shall comply with Sections § 18-29-1106 and § 18-29-1108 of this chapter.
§ 18-29-710.1.2 Minimum size.
The minimum required pipe size for water closets or pedestal urinal branches and stacks shall be 4 inches (100 mm) except that any building three stories or less in height and used exclusively for family unit occupancy, may utilize a 3-inch (75 mm) soil stack when not exceeding 30 fixture units, with not more than two water closets per floor or two water closets per horizontal branch. The waste connection to any water closet shall be provided with an approved 4-inch (100 mm) closet flange. The minimum required sizes for underground branches from downspouts, floor drains, laundry trays and sink stacks shall be 3 inches (75 mm). (See Tables § 18-29-710A and § 18-29-710B.)
§ 18-29-710.1.3 Horizontal stack offsets.
§ 18-29-710.1.4 Vertical stack offsets.
Vertical stack offsets shall be sized as required for straight stacks in accordance with Table § 18-29-710B, except when required to be sized as a building drain in accordance with Section § 18-29-711.1.
§ 18-29-710.2 Future fixtures.
When provision is made for the future installation of fixtures, those provided for shall be considered in determining the required sizes of drain pipes. Construction to provide for such future installation shall be terminated with an approved cap or plug.
§ 18-29-710.3 Underground drainage piping.
Any portion of the drainage system installed underground or below a basement or cellar shall not be less than 4 inches (100 mm) in diameter.
Table § 18-29-710A
Building Drains and Sewers
For SI: 1 inch = 25.4 mm, 1 inch per foot = 0.0833 mm/m.
a) The minimum size of any building drain serving a water closet shall be 3 inches.
Table § 18-29-710B
Horizontal Fixture Branches and Stacks a
For SI: 1 inch = 25.4 mm.
a) Does not include branches of house drain.