Chapter 7 – Sanitary Drainage 1103.407 Amendments to the Uniform Plumbing Code TM – Chapter 7 – Sanitary Drainage. Chapter 7 of the 2015 Uniform Plumbing Code TM is amended by the following provisions. Each section in the UPC that corresponds to one of the following provisions is hereby deleted where so noted or amended to read as set forth below. Each section set forth below without a corresponding provision in the UPC is added thereto. If any conflict of interpretations or requirements of parts or sections of this Chapter disagree with other similar Code provisions or other St. Louis County Ordinance requirements, the more stringent shall apply. 703.0 Size of Drainage Piping. 703.1.1 Exceptions. 1. Any portion of the building drain which is underground and which receives the discharge from a water closet shall be a minimum size of four inches (4") and the four inch (4") pipe size shall terminate at the clean-out thirty-six inches (36") above the finish floor. The minimum size of any other portion of the drainage system, which receives the discharge from a water closet, shall be a minimum size of three inches (3"). (A) Approval may be given by the Authority Having Jurisdiction or his representative to approve the use of a minimum size of three (3”) inches for the discharge of a single water closet when there is no four (4”) inches or larger underground drain readily available. This approval may be given, if such approval does not exceed the capacity of the drain, and, that it would be an undue hardship, or interrupt ongoing business activity, or require extensive demolition of a finished living area, or damage or destroy existing architectural or decorative furnishings. 2. Minimum size of the building sewer shall be six inches (6") in diameter and shall have the minimum of a two (2%) percent slope. 3. No soil or waste stack shall be smaller than the largest horizontal branch connected thereto. A 3x4 inch water closet bend shall not be considered a reduction in pipe size.
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