I like seeing how far water shoots out the hydrant nearest my base of riser. Say that is 10 ft, and the butt is 3 ft high. From The Law of Falling Bodies I know if I drop water straight down from 3 ft it will be going v=SQRT(2gh) when it hits the ground, and the Time of Flight, t=v/g. v=(2*32.2*3)^.5=~14 ft/s. t=14/32.2=.43 s. If the water goes straight out 10 ft in ~half a second it is going 20 ft/s. If the butt is nominal 2.5", smooth and well rounded, (like yours truly): ((2.5/24)^2)*pi=~.034 ft^2, times .9=.031 ft^2, times 20 ft/s=.68 ft^3/s, times 7.48 gallons per cubic foot, times 60 seconds per minute= 305 GPM. So if all I can get is a Purveyor Representative with a hydrant wrench and authorization to quickly, fully open the hydrant and just as quickly, fully shut it down, I'll take it!
Brad Casterline From: Greg McGahan <[email protected]> Sent: Tuesday, September 6, 2022 9:10 AM To: Discussion list on issues relating to automatic fire sprinklers <[email protected]> Subject: [Sprinklerforum] Re: [EXTERNAL] Hydrant flow tests How many flow tests have you seen that underperformed due to a closed valve, broken valve (appeared to be open), disconnected piping that was never reconnected etc? Personally? Too many to not be concerned about solely relying on models. My two cents worth (adjusted for inflation).
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