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Fire Flow Results on 16" pipe

I have modeled a water line extension of a 16" pipe which reduces to 12" and my available fire flows seem high, over 5,000 gpm

Fire flow test yielded 917 gpm @ 66 psi, static @ 67 psi, residual @ 66 psi

My pump curve is setup like this: 0 gpm @ 154.8 feet; 631 gpm @ 153.6 ft & 917 gpm @ 152.5 ft

Lowest available flow is 5,071 (12") & highest is 7,324 (16")  gpm with pressures @ 31.8 & 25.2 psi respectively

I would attach my results but can't see how to do that

Do these numbers seem correct?  They seem high to me for a 16"dip line

Thanks, Ron

  • Ron,

    The available fire flow results are the results when the residual pressure is brought down to 20 psi. Judging by the fact that you had virtually no pressure drop at 917 gpm, the system is very strong. I'm guessing you are close to a tank or a large transmission main.

    Are the 12 and 16 inch pipes dead end pipes or are they in a loop? 5000 gpm in a dead end 16 is only 8 ft/s which isn't way out of range for a fire flow.

    Remember that the reported flow assumes that you have sufficient hydrants to deliver the water. You will need several hydrants or else your fire flow will be hydrant limited.

    Tom
  • This line was extended from another 16" line (tank is probably a couple miles away), not looped
    This 16" line is extended to a tee, stubbed a 16" dead end and other direction is reduced to a 12" that is dead ended which is where the 5000 gpm is, there's 11 hydrants on this line. I looked up the previous watercad file for the line we're connecting to and they had only 1,300 gpm but we had a fire flow test done on this line, it just seems out of whack but I'm not sure. I've never modeled a 16" line so not sure what to expect. thanks for your response