sprinklernotes
A Single FDC Serving Multiple Systems
You asked the following questions: “An AHJ is evaluating a hydraulic calculation for a NFPA 13 compliant fire sprinkler system, which has used CPVC piping. That AHJ is claiming that "run tees shall be included in the hydraulic calculations for all CPVC piping. Supporting data from the Tyco-Fire CPVC data sheet notes that "the need for friction loss for a tee run is only referenced in NFPA 13D under general pipe sizing method section." In our view this does not equate to a mandate for such fittings to be accounted for in an NFPA 13 calculation” In response to your question, we have reviewed NFPA 13, 2016 edition as the applicable standard. Our informal interpretation is that the friction loss for straight through flow is not applied. NFPA 13 section 23.4.4.8.1(5) says, do not include fitting loss for a straight-through flow in a tee or cross. Although the manufacturer has reported a friction loss for a fitting in a straight through flow condition, NFPA 13 indicates that this data is not required to be included in the hydraulic calculations. This data is provided because in some cases it is necessary to include the manufacturers data for fittings in a straight through flow condition. One such case is when the designer uses non-metallic pipe and pipe sizing procedures in accordance with NFPA 13D section 10.4.1 and 10.4.2.3. NFPA 13D section 10.4.1 explicitly states that for specially listed piping products the friction loss for pipe and fittings shall be permitted to be calculated based on the manufactures data. In other words, if the designer is using listed CPVC pipe and fittings and NFPA 13D section 10.4 pipe sizing criteria, the CPVC manufacturers data for friction loss straight through a tee must be included in the calculations. Another such case is when the designer uses 1/2-inch nonmetallic and 1/2-inch copper pipe. NFPA 13D section 10.4.2.3(6), The system shall be hydraulically calculated in accordance with NFPA 13 except the friction loss straight through the fitting shall be included.
