4.08 Design Criteria for Installation of Underground Piping for Fire Sprinkler Service

Reference: 2007 C.B.C. Sec. 903

2002 NFPA 24, section 10.4.3, requires that the depth of cover for fire service main pipe be not less than 30 inches or one foot below the frost line for the locality. Where frost is not a factor, the 30 inch depth of cover is required to protect the pipe from mechanical damage.
The San Francisco Water Department supplies domestic water meters for all fire services of two-inch and smaller, including combination fire/domestic services. These meters require that the pipe be installed less than the 30 inches required by NFPA 24.
Due to the practical difficulty of compliance with this standard, all two-inch and smaller fire services, including combination services, shall be allowed to be installed following the criteria listed below which will prevent mechanical damage:

1. All installation of piping shall comply with San Francisco Plumbing Code section 609.1 which requires a minimum depth of cover of 12 inches below finished grade.
2. A minimum four inches of concrete shall cover the area above the pipe. The four inch concrete installation shall extend a minimum of 12 inches horizontally on both sides of the pipe.
3. A minimum of three inches of earth shall be maintained between the pipe and concrete. Exception: Pipe and joints that have been coated and wrapped do not have to comply with this requirement.