Note: the elevation head must be taken into account if the inlet and outlet are at different elevations.

Elevation head is due to the fluid's weight, the gravitational force acting on a column of fluid.

Pressure head is a component of hydraulic head, in which it is combined with elevation head.

The total hydraulic head of a fluid is composed of pressure head and elevation head.

Thus, the three terms of velocity head, elevation head, and pressure head appear in the head equation derived from the Bernoulli equation for incompressible fluids:

The pressure head is the equivalent gauge pressure of a column of water at the base of the piezometer, and the elevation head is the relative potential energy in terms of an elevation.

The energy equation used for open channel flow computations is a simplification of the Bernoulli Equation (See Bernoulli Principle), which takes into account pressure head, elevation head, and velocity head.