Select required Head. Move horizontally to intersect pump Head-Capacity
Move vertically from intersection point on Head-Capacity line to
read Gallons per Minute.
From intersection point of vertical line with the BHP (Brake Horsepower)
line, move horizontally to the BHP scale for required Horsepower.
As a general rule, size the pump to operate near its best efficiency
point which is typically between 50% to 80% of its maximum capacity.
When using multi-stage pump curves, select the number of stages that
will not only provide the desired flow rate, but one that will operate
at greater than 50% of its maximum flow rate to obtain longest life and
lowest horsepower requirements.
The four stage is the best selection for the curve illustrated. The
three stage selection would be considered fair at 40% of maximum capacity
and the two stage would not be recommended.