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Volume Flow our of a fire hydrant

  1. Jan 24, 2005 #1
    I'm doing calculations for how much water was lost during flushing a hydrant. It is a 2.5 in. outlet and the pressure is on the system in that zone is 40 psi. It was flushing for 1.5 hours.


    V=[(2 dP gc)/density]

    density = 62.4 lb/ft^3
    dP=40 psi
    gc=32.2 lbm ft / lbf s^2


    Q=AV=(0.0340)(77)=2.6 ft^3/s=19gal/sec

    The hydrant was flushing for 1.5hrs=90mins=5400secs so...

    The water lost was 19*5400=105,892.77 gals??? is that right?? can you check my generals theory of my problem?? it seems to me a little bit high to loose 100,000 gals in 1.5 hours for flushing a hydrant... don't you think?
  2. jcsd
  3. Jan 25, 2005 #2


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    Science Advisor

    This was answered on Eng-tips forum. I'd look there instead of rehashing it here as well.
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