Every automatic sprinkler system shall have at least one automatic water supply.
Except as provided in 24.1.3.2, no pipe smaller than 6 in. (150 mm) in diameter shall be installed as a private service main.
For mains that do not supply hydrants, sizes smaller than 6 in. (150 mm) shall be permitted to be used subject to the following restrictions:
- The main supplies only automatic sprinkler systems, open sprinkler systems, water spray fixed systems, foam systems, or Class II standpipe systems.
- Hydraulic calculations show that the main will supply the total demand at the appropriate pressure. Systems that are not hydraulically calculated shall have a main at least as large as the system riser.
When a single main less than 4 in. (100 mm) in diameter serves both domestic and fire systems, the domestic demand shall be added to the hydraulic calculations for the fire system at the point of connection unless provisions have been made to isolate the domestic demand.
For pipe schedule systems, the underground supply pipe shall be at least as large as the system riser.
Water supplies and environmental conditions shall be evaluated for the existence of microbes and conditions that contribute to microbiologically influenced corrosion (MIC). Where conditions are found that contribute to MIC, the owner(s) shall notify the sprinkler system installer and a plan shall be developed to treat the system using one of the following methods:
- Install a water pipe that will not be affected by the MIC microbes
- Treat all water that enters the system using an approved biocide
- Implement an approved plan for monitoring the interior conditions of the pipe at established time intervals and locations
- Install corrosion monitoring station and monitor at established intervals
Water supplies and environmental conditions shall be evaluated for conditions that contribute to unusual corrosive properties. Where conditions are found that contribute to unusual corrosive properties, the owner(s) shall notify the sprinkler system installer and a plan shall be developed to treat the system using one of the following methods:
- Install a water pipe that is corrosion resistant
- Treat all water that enters the system using an approved corrosion inhibitor
- Implement an approved plan for monitoring the interior conditions of the pipe at established intervals and locations
- Install corrosion monitoring station and monitor at established intervals
Where listed biocides and/or corrosion inhibitors are used, they shall be compatible with system components. Where used together, they shall also be compatible with each other.
The connection between the system piping and underground piping shall be made with a suitable transition piece and shall be properly strapped or fastened by approved devices.
The transition piece shall be protected against possible damage from corrosive agents, solvent attack, or mechanical damage.
When system piping pierces a foundation wall below grade or is located under the foundation wall, clearance shall be provided to prevent breakage of the piping due to building settlement.
Where meters are required by other authorities, they shall be listed.
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The requirements of the public health authority having jurisdiction shall be determined and followed.
Where equipment is installed to guard against possible contamination of the public water system, such equipment and devices shall be listed for fire protection service.
Water supplies for sprinkler systems shall be one of the following or any combination:
- A connection to an approved public or private waterworks system in accordance with 24.2.2
- A connection including a fire pump in accordance with 24.2.3
- A connection to a water storage tank at grade or below grade installed in accordance with NFPA 22 and filled from an approved source
- A connection to a pressure tank in accordance with 24.2.4 and filled from an approved source
- A connection to a gravity tank in accordance with 24.2.5 and filled from an approved source
- A penstock, flume, river, lake, pond, or reservoir in accordance with 24.2.6
- *A source of recycled or reclaimed water where the building owner (or their agent) has analyzed the source of the water and the treatment process (if any) that the water undergoes before being made available to the sprinkler system and determined that any materials, chemicals, or contaminants in the water will not be detrimental to the components of the sprinkler system it comes in contact with
A connection to a reliable waterworks system shall be an acceptable water supply source.
A single automatically controlled fire pump installed in accordance with NFPA 20 shall be an acceptable water supply source.
A pressure tank installed in accordance with NFPA 22 shall be an acceptable water supply source.
Pressure tanks shall not be used to supply other than sprinklers and hand hose attached to sprinkler piping.
The total volume shall be based on the water capacity plus the air capacity required by 24.2.4.3.
Pressure tanks shall be kept with a sufficient supply of water to meet the demand of the fire protection system as calculated in Chapter 23 for the duration required by Chapter 11, Chapter 12, or Chapter 22.
The pressure shall be sufficient to push all of the water out of the tank while maintaining the necessary residual pressure (required by Chapter 23) at the top of the system.
An elevated tank installed in accordance with NFPA 22 shall be an acceptable water supply source.