What is the difference between pressure head and pressure?

Applies To
Product(s): WaterCAD, WaterGEMS, HAMMER
Version(s): V8i, CONNECT Edition
Area: Output and Reporting
Original Author: Mark Pachlhofer, Bentley Technical Support Group

 

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?

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