Energy grade line (EGL) (energy line, energy gradient)

The line showing the total energy at any point in a pipe. The total energy in the flow of the section with reference to a datum line is the sum of the elevation of the pipe centerline, the piezometric height (or pressure head), and the velocity head. The energy grade line will slope (drop) in the direction of flow except where energy is added by mechanical devices. The line representing the elevation of the total head of flow is the energy line. The slope of the line is known as the energy gradient. See hydraulic grade line.