You asked the following question: “The water supply is coming from a common water meter that serves the domestic water supply needs as well as the fire sprinkler system. Do I include 5 gpm for domestic demand in the hydraulic calculations for a single family dwelling?” In response to your question we have reviewed NFPA 13D, 2013 edition as the applicable standard and the 2013 editions of the California Residential Code (CRC) and the California Fire Code. Our informal interpretation is that 5-gpm is added where the water supply serves both domestic and fire sprinkler systems per the CRC.
Section 3.1.3.2.1 states, “Automatic residential fire sprinkler systems shall be designed and installed in accordance with Section R313 or NFPA 13D.” Section R313.3.1 indicates that the design and installation of residential fire sprinkler systems shall be in accordance with NFPA 13D or Section R313.3, which shall be considered equivalent to NFPA 13D. As such, a system can be installed per R313.3 or NFPA 13D. When the method of R313.3 is used, Section R313.3.5 says that the water supply shall provide not less than the required…show more content… Where a water supply serves both domestic and fire sprinkler systems, 5 gpm shall be added to the sprinkler system demand at the point where the systems are connected, to determine the size of common piping and the size of the total water