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9/22/2017 12:11:25 AM
Posted: 8/10/2005 3:27:39 PM EDT
My pump has a 3" discharge and at 20' high it is advertised to flow 120 gpm.

I calculated that a 3"column of water 20' tall weighs 58.73#. Does this mean that at 0' it will produce 58.73 psi @120 gpm?

Thanks for any help.
Link Posted: 8/10/2005 3:38:50 PM EDT
[Last Edit: 8/10/2005 3:39:06 PM EDT by Kharn]
Its been 2 years since Fluid Mechanics and all my books are at my parents', but I believe you'll get a lot more water flow, not a higher pressure.

Link Posted: 8/10/2005 3:41:51 PM EDT
[Last Edit: 8/10/2005 3:44:58 PM EDT by nightstalker]
You're pushing 58.73 pounds of water but the surface area of the column is not a square inch. Surface area is about 7 sq in.

You're going to be asking the pump to do a lot less going sideways rather than the work of vertical lifting or pumping.
Link Posted: 8/10/2005 6:22:23 PM EDT
Every centrifugal pump has a pump curve. This "curve" is basically a chart that shows the pumps flow rate at a given head condition. (The head conditon is the difference in height from the existing water level to the highest point you are pumping) If you ask the manufacturer for this curve they should be able to provide it.

The pump will definitely pump more at a lower height, but it is really impossible to determine what the pump will pump from the information provided. Depending on the type of pump, it may not even work at 0' of head.

FYI a 20' high column of water = 8.6psi.
You divide head by 2.31 to get psi.

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