5. Pump Sizing and Power Requirements

Pump Sizing and Power Requirements Objectives:

• You will learn the two functions of a pump.
• You will learn the two pieces of information required to select a pump.
• You will study and appreciate the energy requirements (work to be done) for a pump to accomplish its work.
• You will be familiar with information provided by a pump chart.
• You will understand efficiency and power requirements for a pump powerplant.

A frequent question I receive from a farmer, nurseryman, or greenhouse operator about pumps is, How many horsepower pump do I need?

The pump must do two things:

  1. move the required quantity of water, and
  2. create sufficient pressure to make the system work.

These, then, are the two factors involved in selcting a pump. A pump typically must lift water from a lower level and then push it to a higher level with enough force to make the sprinkler nozzles or trickle emitters work properly.

In addition, the power plant - either an electric motor or an engine - must be sized to operate the pump to achieve the flow and pressure. There is a two-step process to sizing the correct pump for a job.

The power plant is not 100 percent efficient due to losses in power transmission. The power unit needs to be a have greater horsepower than required by the pump in order to provide adequate usable power.