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NFPA 13 (2013) 8.17.4.6.2 Interpretation

Question asked by jamila on Sep 29, 2020
Latest reply on Oct 1, 2020 by mo.tabarrok

Hello Dear Community,

 

I have a question with regards to the following interpretation of a Code in NFPA 13 - 2013 Edition:

 

8.17.4.6.2 Retroactive Installation. When backflow prevention devices are to be retroactively installed on existing systems,
a thorough hydraulic analysis, including revised hydraulic calculations, new fire flow data, and all necessary system
modifications to accommodate the additional friction loss, shall be completed as a part of the installation.

 

My questions are:

1. What constitutes a thorough hydraulic analysis?

2. What is the definition of new fire flow data? Does it refer to a hydrant test or fire pump test if there is a fire pump?

 

From my experience, sometimes it can be obvious that a backflow preventer will not cause severe system pressure loss to the extent that the sprinkler heads in the most demanding area will not meet the pressure and flow requirements of NFPA 13. The manufacturer's flow curve for backflow devices states the pressure loss at a fixed flow and considering that most sprinkler systems are designed with a safety margin, it doesn't seem necessary that a revised hydraulic calculation is required. Sometimes it can be very clear from the hydraulic plaque (signage) or previous hydraulic calculations that there is enough pressure to accommodate future system losses. Does this constitute as a "thorough hydraulic analysis" and can this be considered as completing a "revised hydraulic calculation"?

 

Thank you in advance for your support and help.

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