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NFPA 1: Minimum Number of Fire Hydrants for Fire Flow #FireCodefridays

Blog Post created by kristinbigda Employee on Sep 16, 2016

Section 18.5 of NFPA 1 provides requirements for fire hydrants, including location, distribution, minimum number, clearance, marking, and testing and maintenance.

 

Section 18.5 was revised in its entirety for the 2015 edition of the Code. Previous editions provided a performance-based requirement that the number and type of fire hydrants and connections to other approved water supplies be capable of delivering the required fire flow and be provided at approved locations. The former Annex E was deleted for the 2015 edition of the Code; in its place, Section 18.5 was revised by the addition of prescriptive, mandatory requirements for fire hydrant location and distribution based on the required fire flow determined in accordance with Section 18.4.

 

To determine the minimum number of fire hydrants for fire flow, the following provisions should be followed:

  • The aggregate fire flow capacity of all fire hydrants within 1000 ft (305 m) of the building cannot be less than the required fire flow.
  • Table 18.5.4.3 provides the maximum fire flow capacity for which a fire hydrant can be credited.

hydrant.JPGExample:

Determine the number of required fire hydrants for a proposed, new manufacturing building with a fire area of 50,000 ft2 (4650 m2) and a construction classification of Type II(000) (noncombustible and unprotected). The building will be protected throughout by an approved automatic sprinkler system with standard response sprinklers.

 

Sample Solution:

Test results indicate the theoretical available fire flow is 3500 gpm. Based on the procedures as outlined in Section 18.4, the required fire flow is approximately 1200 gpm.

 

  • A designer chooses to locate one fire hydrant on the existing public water mains at a distance of 350 ft (107 m) from the building, which meets the maximum 400 ft (122 m) distance criterion of 18.5.3(1).
  • Using Table 18.5.4.3, it is determined that a hydrant located 400 ft (122 m) from the building can be credited with not more than 1000 gpm (3785 L/min). Because this is less than the required fire flow of 1200 gpm (4500 L/min), one additional hydrant is required within 1000 ft (305 m) of the building. (Or the designer could choose to extend a private fire service main onto the property and locate a hydrant at a distance of not more than 250 ft (76 m) from the building.)
  • In accordance with Table 18.5.4.3, such a hydrant would be permitted to be credited with up to 1500 gpm (5678 L/min), which exceeds the required fire flow of 1200 gpm (4500 L/min).
  • If the designer chooses to add a second hydrant on the public main, they should be spaced so the distance between them does not exceed 500 ft (152 m) in accordance with 18.5.3.
  • The AHJ should require an additional flow test following the installation of the new hydrant or hydrants to verify they are capable of delivering the required fire flow.

 

A little over two weeks until the NFPA 1 Second Draft meeting, next week I will talk about issues the committee will be addressing in Milwaukee on October 3-4 (check out the agenda at www.nfpa.org/1next)

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