The total head HBN, calculated from a datum level BN, is the mechanical energy of the fluid handled, per unit weight. The unit of total head is metres (m).
z Geodetic height of given point above BN
pb Atmospheric pressure
p Overpressure (positive) or underpressure (negative) in relation to pb
ρ Density of fluid handled
g Gravitational acceleration
v Flow velocity
A graphic representation of the total head at various points within a pump system can be found in EN 12723, for example. See Fig. 1 Specific energy