Fire Hydrant Flow

[civil95eng]

I have been tasked to calculate the fire flow at a new hydrant for a project. Currently there is a 12-inch waterline at the street. I have to extend 500ft of 8-inch line with a double detector check on the line and a fire hydrant at the end of the line to near my new building. The city has asked to make sure that there is adequate fire protection which means that at least 1500 gpm at 20 psi is available at the fire hydrant. We just did fire flow test using two hydrants on the 12" main. The results were 108 psi - static; 78 psi - residual; 55 psi - pitot with a calculated flow rate of 1106 gpm. I have the headlosses for the line and the detector check, but I am not sure how to calculate if there is at least 1500 gpm at 20psi at the new hydrant. I know there is a simple calculation to determine if there is adequate fire flow available. Any help would be greatly appreciated. Thanks.

 

[MGXFP]

Just do a search of this subforum for 1.85 graph paper or to find the equation. I prefer to use the graph paper since per NFPA 291 you only need to round to the nearest 100 gpm anyways if flows exceed 1000gpm for reporting.

 

[cdafd]

Not sure if this works

And adjust for the run of pipe

http://www.firehydrant.org/info/hycalc.html