sprinklernotes Maximum Set Pressure for Pressure-Regulating Devices “We have a fire pump house supplying a facility containing multiple sprinkler systems and a standpipe system. We are providing a pressure-reducing valve (PRV) in the pump house downstream of the pump control valve to control the pressure to the downstream standpipes. Am I required to restrict the outlet pressure of the PRV to 165 psi as dictated by NFPA 13 section 16.9.8.1?”
In response to your question, we have reviewed NFPA 13 Standard for the Installation of Sprinkler Systems, 2019 edition and NFPA 14 Standard for the Installation of Standpipe and Hose Systems, 2019 edition as the applicable standard. Our informal interpretation is depending on the piping arrangement, the PRV could be set at 165 psi if it serves the sprinkler system or 175 psi if it is dedicated to the standpipe system. For a combined system, the PRV would be required to meet the requirements of NFPA 13 and NFPA 20 since it serves both systems. Per NFPA 13: 16.9.8.1 In portions of systems where all components are not listed for pressure greater than 175 psi (12 bar) and the potential exists for normal (nonfire condition) water pressure in excess of 175 psi (12 bar), a listed pressure-reducing valve shall be installed and set for an outlet pressure not exceeding 165 psi (11 bar) at the maximum inlet pressure. Per NFPA 20: 7.1.1* When pressure-regulating devices are used, they shall be approved for installation within the maximum and minimum anticipated flow conditions. 7.2.4(3) To provide redundancy, pressure-regulating devices shall be arranged in series so that the failure of any single device does not allow pressure in excess of 175 psi (12.1 bar) to any of the multiple hose connections downstream. While standpipe systems permit pressures up to 175 psi, a combined system would be required to have the PRV set at 165 psi to satisfy the requirements of both NFPA 13 and NFPA 14. In addition to the set pressure, NFPA 20 requires redundancy when multiple hose connections are supplied by a pressure regulating device per section 7.2.4.
