What is the difference between pressure head and pressure in WaterCAD and WaterGEMS?
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.
When the user changes the fluid, why doesn't the calculated pump head change?