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Applies To |
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Product(s): |
WaterCAD, WaterGEMS, HAMMER |
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Version(s): |
V8i, CONNECT Edition |
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Area: |
Output and Reporting |
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Original Author: |
Mark Pachlhofer, Bentley Technical Support Group |
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Problem
What is the difference between pressure head and pressure in WaterCAD and WaterGEMS?
Solution
Pressure head is the hydraulic grade minus the physical elevation at a junction or the weight of a given height of water column at its bottom end. It is independent of the amount of water: the pressure head of a 10-foot high or deep 2-inch diameter pipe is the same as that of the 2-foot diameter pipe of the same height or depth (business dictionary.com, 2014).
The pressure is the hydraulic grade minus the physical elevation at a junction, but also takes into account the specific gravity of water, which defaults to 0.998. For example, if you have a pressure head of 56.70ft your pressure would be 56.79ft * 0.998 = 56.67 ft of H20.
See Also
When the user changes the fluid, why doesn't the calculated pump head change?