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Fire Department Connections on Home Fire Sprinkler Systems
National Fire Protection Association's Standard 13D, the standard for home fire sprinkler systems, does not require a fire department connection, but they are allowed. Occasionally a local fire department wants a home fire sprinkler system to have a fire department connection. When a fire department connection is used on a home fire sprinkler system, then section 4.3.2 of the 2007 edition of NFPA 13D states that the system must pass a hydrostatic pressure test in accordance with NFPA 13. The NFPA 13 hydrostatic pressure test is done according to NFPA 13, (2007 edition), section 24.2.1, which is basically at 200 psi for 2 hours.
This system should handle this pressure with no problem, unless the fire sprinkler system is interconnected with the plumbing, such as in Kwench, Uponor/Wirsbo, and Rehau fire sprinkler systems. The pressure would then blow apart the domestic plumbing. There are 2 ways however that this may be accomplished:
One is to test the fire sprinkler system before the system is interconnected with the domestic plumbing. Pressure from the pumper truck should not exceed 130 psi if pex pipe is used for the fire sprinkler system. If the fire department pumps water into the system during a fire, then the plumbing fixtures are apt to get damaged, and some water will be lost through them, but plenty of water will get to the fire sprinkler heads.
The other method that our office accepts is to add a pressure-reducing valve between the fire department hook-up and the fire sprinkler system. The pressure reducing valve does not need to exceed 1.5", regardless of the size fire department connection on the outside of the house. This pressure-reducing valve must limit the pressure from the pumper truck to no more than 130 psi. This is because NFPA 13D, section 220.127.116.11 states that "Nonmetallic pipe used in multipurpose piping systems not equipped with a fire department connection shall be designed to withstand a working pressure of not less than 130 psi (8.9 bar) at 120°F (49°C)." (Note that NFPA refers to a fire sprinkler system interconnected with domestic plumbing as a "multipurpose piping system".)
If the fire sprinkler system piping is not interconnected with plumbing, then section 18.104.22.168 of NFPA 13D requires the pipe to be designed to withstand a working pressure of not less than 175 psi, typical of NFPA 13 systems for commercial buildings. Pex pipe is listed for less than 175 psi, but more than 130 psi. Its burst pressure at room temperature is far above 200 psi, so it should take the 200-psi-for-two-hours-test with no problem at all. The reason for the higher pipe rating is because of the higher pressures that come from a fire department pumper truck. The pressure-reducing valve set to not exceed 130 psi limits this pressure to what it should be without the fire department connection.
This is not an exact NFPA code exception, but where the code does not require a fire department connection, the state does not either, and in this case we would use section 1.6.1 and 1.6.2 from NFPA 13, (2007) as a code backing to justify the use of a pressure-reducing valve that is not listed for fire service. These sections state:
Water districts and plumbing regulations do not want fire department connections on homes, because of potable water contamination from the fire truck. Any town wanting to add the fire department connections to these home systems must check with the plumbing officials. The domestic water supply from a well however can easily be treated with a bleach solution after a fire event.
If local authorities do not feel strongly one way or the other about requiring fire department connections on homes, then our suggestion is to not require them. The code does not require them, and keeping the cost down is important in promoting residential fire sprinkler systems.
[Last updated 1-1-08]
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