A project requires a pump that will operate with a minimum discharge of 20 L/ sec against an elevation head of 40 m. The distance between the supply and delivery points is l 50 m. A ball check valve will be used in the system that consists of commercial steel pipes. Determine the most economical pipe diameter for the pipeline and select a single pump from Figure 5.24 (including its operating conditions) if the total cost can be expressed as
C = d 1.75 + 0.15 P + 18
where dis the pipe diameter in centimeters and P is the pump horsepower input.