Combined Sanitary and Storm System
NYC Plumbing Code § PC 1109
in effectSection PC 1109: Combined Sanitary and Storm System
1109.1 Size of combined drains and sewers.
Combined sanitary and storm sewers are not permitted in new installations. All sanitary and storm systems shall be separate up to a point located in accordance with the applicable requirements of the Department of Environmental Protection. With respect to repair of combined systems installed prior to the effective date of this section, the size of a combination sanitary and storm drain or sewer shall be computed in accordance with the method in Section 1106. The fixture units shall be converted into an equivalent projected roof or paved area. Where the total fixture load on the combined drain is less than or equal to 256 fixture units, the equivalent drainage area in horizontal projection shall be taken as 1,333 square feet (124 m2). Where the total fixture load exceeds 256 fixture units, each additional fixture unit shall be considered the equivalent of 5.2 square feet (0.48 m2) of drainage area. These values are based on a rainfall rate of 3 inch (75 mm) per hour.
Source: City of New York, Charter, Administrative Code and Rules (American Legal Publishing XML export, codelibrary.amlegal.com)URL: https://codelibrary.amlegal.com/codes/newyorkcity/latest/NYCadmin/0-0-0-163479Fetched: 10/24/2026