WSRCA Technical Bulletin 2017-ILS&W3: 2015 IPC Updated Storm Drainage Design Methodology

The Western States Roofing Contractor’s Association (WSRCA) has prepared this Technical Bulletin to advise WSRCA Members of new changes to the 2015 International Plumbing Code (IPC), for those States or Jurisdictions that have or will be adopting the updated Code.

Not all states within the Western United States adopt the IPC so please be aware of the specific codes and editions that are in effect for your given project. For instance, States such as California and Washington have utilized the Uniform Plumbing Code (UPC) as the basis for their plumbing codes. The series of Code editions are typically updated on a three-year development cycle and for those States and Jurisdictions that adopt the 2015-series of codes, including the IPC, the 2015 series are typically already in effect.

Background Information: For States and Jurisdictions using the IPC, substantial new changes have been introduced in the updated 2015 International Plumbing Code related to methods for calculating and sizing of roof drains, drain leaders/drain pipelines, and storm drainage systems. Many of these changes were influenced by a potentially groundbreaking research project conducted by the American Society of Plumbing Engineers (ASPE) Research Foundation entitled, Storm Drainage System Research Project – Flow Rate Through Roof Drains. WSRCA’s Technical Bulletin discusses the research and studies that challenged decades old assumptions and design standards resulting in many of the new roof and deck drainage design methodologies, including new design standards, tables, and requirements for storm water drainage to reflect and address the new research findings.  Click here to continue.

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