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Join Date: Jul 2009
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# Water Main

07/10/2009 9:11 AM

Does anyone know what the flow rates are for water running through a water "MAINS" at peak hours? 12 inch pipes that deliver 1000 gallons a minute ? Formular please. Thanks

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Guru

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#1

### Re: Water Main

07/10/2009 9:25 AM

Well, the Darcy-Weisbach equation can be used to relate flow to pressure drop, Captain. Is that what you want?

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#2

### Re: Water Main

07/10/2009 10:18 AM

12 inch pipes that deliver 1000 gallons a minute
Errr, That would be 1000 gallons a minute...
Do I get a prize?
I don't think we understand the question....
Del

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#3

### Re: Water Main

07/10/2009 11:11 AM

Is this what you're looking for? Maximum allowable water velocity X cross-sectional area of pipe = maximum allowable volumetric flow rate of water. Maximum allowable velocity determined by maximum allowable pressure drop as calculated by the Darcy-Weisbach equation suggested by Crabtree (who really should stick to speaking English; his spoken French absolutely stinks) or the Hazen-Williams equation.

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#4

### Re: Water Main

07/10/2009 12:33 PM

That works for me! Thanks, thats what I was looking for The Darcy-Weisbach equation. And Yes the prize goes to previous poster that yes 1000 gallons a minute is the flow rate. Real funny! What's the pressure for the given flow rate? and how much head is needed to achieve that rate?

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#6

### Re: Water Main

07/12/2009 2:53 AM

You're confusing pressure and flow rate. When you size a pump, you compare the flow against the pressure in the pump curve, and then select the pump that comes closest to meeting specifications. As to what the required pressure that the pump must supply, it is required pressure at point of use + frictional losses in pipe (as calculated by the Darcy-Weisbach or Hazen-Williams equations) + frictional losses in equipment (generally speaking, about 10psi per piece of equipment) + vertical head. As every pressure requirement varies with application, this is the best answer I can give you.

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Join Date: Mar 2009
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#5

### Re: Water Main

07/11/2009 7:34 AM

You need the actual numbers? Then go to the Manufactor's web site. PVC is different than ductile iron...age of pipe, junctions, you must include any conflict boxes and of course...gravity lines or what type of a pumping station and how far from that...etc. Not really hard to figure out. KISS formula -

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#7

### Re: Water Main

07/12/2009 10:55 PM

Try:

http://www.engineeringtoolbox.com/hazen-williams-water-d_797.html

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