Volume Flow our of a fire hydrant

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SUMMARY

The discussion focuses on calculating the volume of water lost during the flushing of a fire hydrant with a 2.5-inch outlet at a pressure of 40 psi over a duration of 1.5 hours. Using the formula Q=AV and the velocity equation V=[(2 dP gc)/density], the calculated flow rate is 2.6 ft³/s, which translates to approximately 19 gallons per second. Over 1.5 hours, this results in a total water loss of 105,892.77 gallons. The accuracy of this calculation was questioned, suggesting that the figure may seem excessively high for a hydrant flushing.

PREREQUISITES
  • Understanding of fluid dynamics principles
  • Familiarity with the formula Q=AV for flow rate calculations
  • Knowledge of pressure units, specifically psi
  • Basic understanding of density in fluid mechanics
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  • Research the implications of flushing hydrants on municipal water supply systems
  • Learn about pressure loss calculations in piping systems
  • Investigate the effects of different outlet sizes on flow rates
  • Explore methods for measuring actual flow rates in field conditions
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Water resource engineers, municipal water system operators, and anyone involved in hydraulic calculations or fire safety management will benefit from this discussion.

lord_temple
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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.

Q=AV

V=[(2 dP gc)/density]

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

V=77ft/s

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

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