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Fire Flow Requirement

Question asked by ishrestha on Oct 18, 2018

My question is regarding NFPA Fire Code 18.4.5.3 “Building Other Than One and Two-Family Dwellings” and Code 18.5.4 “Minimum Number of Fire Hydrants for Fire Flow.

 Proposed scenario:

80,000 Square Foot Class II building is proposed for the future development. Per NFPA Table 18.4.5.2.1, minimum required fire flow is 6000 gpm for 4 hour.

Fire flow test was conducted near the project site. Per Fire flow test; two (2) hydrant was used, flowing hydrant had two 2.5” outlet open. The static pressure was 90 psi, residual pressure was 79 psi, and pitot reading was 38 psi. Based on this data, the available fire flow at 20 psi is 5625 gpm.

Does this mean that it does not meet the fire flow requirement per NFPA Table 18.4.5.2.1 (6000 gpm)? What if we are planning to provide the fire loop around the building and fire hydrant at every 350 feet? Will this satisfy the NFPA requirement?

I am little confused, Per NFPA Code 18.5.4.2, aggregate fire flow capacity of all fire hydrant within 1000 ft of the building, measured in accordance with 18.5.1.4 and 18.5.1.5 shall be not less than the required fire flow determined in accordance with Section 18.4.

If I plan to propose a fire loop around the building with fire hydrant at every 350 feet and fire flow test near project verified that fire flow capacity of existing hydrant is 5625 gpm, will this not satisfy the fire flow requirement per NFPA. (almost 2X5625 gpm = 11250 gpm (NFPA code 18.5.4.2)

Please advise! I look forward for your reply and suggestion.

To summarize my question:

  1. fire flow requirement per table 18.4.5.2.1 is from one hydrant or combination of hydrant?
  2. Can I multiply the fire flow test results from project vicinity, if I plan to add fire loop with at minimum 2 hydrant at every thousand feet?

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