In Part I of this three-part series we reviewed the basics of residential sprinkler systems with a focus on the standalone sprinkler system based on the National Fire Protection Association (NFPA) 13d standard. As residential sprinklers become the norm in many new homes, it is important for firefighters and company officers to understand the various systems and design information.
As firefighters, we are used to utilizing NFPA documents for providing technical information for firefighter safety, requirements for turnout gear, or apparatus. There are hundreds of documents that cover fire suppression, fire alarm systems, or fire doors. As related to residential sprinklers in new homes, the standard is set by NFPA 13d: The Standard for the Installation of Sprinklers in One and Two Family Dwellings and Manufactured Homes sets the standard. This standard provides the basis for the installation of all residential sprinklers in homes and the standalone system utilizes separate piping from the plumbing system.
These systems allow a separate design with separate piping. It is critical to remember the intent of NFPA 13d (NFPA 13d 1.2):
The purpose of this standard shall be to provide a sprinkler system that aids in the detection and control of residential fires and thus provides improved protection against injury, life loss, and property damage. A sprinkler system designed and installed in accordance with this standard shall be expected to prevent flashover (total involvement) in the room of fire origin, where sprinklered, and to improve the chance for occupants to escape or be evacuated. The layout, calculation and installation of systems installed in accordance with this standard shall only be performed by people knowledgeable and trained in such systems.
The intent statement gives many keys to success of the system. First, the 13d-based sprinkler system, which is designed to prevent flashover. Flashover occurs in fires where everything in a room is consumed by fire. Flashover is a very dangerous condition that could result in loss of life if allowed to occur. The systems are to provide a chance for occupants to escape or be evacuated.
Looking at the last line of the intent statement, it clarifies requirements for installation, “layout, calculation and installation of the systems installed in accordance with this standard shall only be performed by people knowledgeable and trained in such systems.” Local and state rules may require additional clarification on who can install such systems. In a multipurpose system, the plumbing designer, contractor and sprinkler designer will work closely together to provide the complete package. The plumbing contractor is concerned about typical installation, while the sprinkler contractor needs to ensure adequate pressure are available at the most remote sprinklers.
The standard is intended to provide multiple approaches for homeowners and contractors in providing sprinklers. These include standalone, multipurpose, and listed pex-type systems. Multipurpose systems provide an opportunity to keep installation and material costs a little lower. The system name describes the intent of the system and that it is to use the same piping that feeds the bathroom, kitchen and other appliances to feed the residential sprinkler systems.
NFPA defines a Multipurpose system as (3.3.9.3) “A piping system intended to serve both domestic and fire protection needs.” In simple terms, if it has water, it is fed from the multipurpose system.
Remember, home fire sprinkler systems are much like plumbing systems. They require proper installation and need to be maintained properly. When this occurs, there is a very low risk of leaks or other problems. Think of your own home, if your plumbing system was installed correctly, has it leaked behind a wall?
Each individual sprinkler is designed to activate only when it senses a significant heat change. When the temperature reaches the design temperature of the sprinkler, only the sprinkler near the heat source will activate and discharge approximately 18 gallons a minute (volumes may change based on type of sprinkler and water supply).
Key Items for Multi-purpose Systems:
1. In duplex situations, where there is more then one dwelling unit, the designer will add 5 gpm to the sprinkler system demand to determine the size of the common piping and total water supply requirements.
2. Piping shall be listed and conform to the piping specifications listed in the standard. Piping that supplies only the plumbing fixtures shall comply with the local plumbing code and is not required to be listed.
3. The systems must be allowed by the local plumbing official. The installation company shall install a warning sign that indicates, “Warning, the water system for this home supplies fire sprinklers that require certain flows and pressures to fight a fire. Devices that restrict the flow or decrease the pressure or automatically shut off the water to the fire sprinkler system, such as water softeners, filtration systems and automatic shutoff valves, shall not be added to this system without a review of the fire sprinkler system by a fire protection specialist. Do not remove this sign.”
4. Any restriction of water through filtration systems is to be considered in the design.
5. An automatic bypass is to be installed in the water treatment equipment that directs all water to the system.
Recent Changes
The 2002 edition included changes that established a minimum design discharge density. The requirements for multipurpose systems were changed to require a bypass valve for installations with water softeners or water filtration equipment installed and to update the requirements for network systems.
Residential sprinkler systems can be installed in many different ways. It is critical for first arriving firefighters to quickly size up the type of system, ensure the fire is extinguished (follow standard structure fire response protocol) and determine the best action with the system.
Part III will look closely at other systems and types.
