Pumps

The main unit on an irrigation system is the pump. There are three main implications when selecting the correct irrigation system. These implications are what will determine all factors from cost to size. These implications are the source of the water, the piping, and their components. From all different pump types, the main pumps used in irrigation systems are centrifugal pumps specifically the following sub-types:

• Horizontal Single Stage
• Propeller
• Deep Well
• Submersible

What determines what kind of pump is used in the irrigation system is the water source. It will be surface water (like rivers, lakes, Rain collection tanks, and ponds), underground water, or a mixture of both. The size of the pump will be determined primarily by the amount of required flow, and the total dynamic head of the system (TDH). To determined the Total Dynamic head, you will need to add in Length measure (Feet, meters, etc) from the water level to the highest point the water will have to be raised for the irrigation plus the total pressure requirement for the sprinkler head to work plus the friction loss. In order to change head pressure from the sprinkler head to feet, you will ne to multiply the total psi requirement times 2.31. The Friction losses can be determined from Friction loss tables. In cases where the pump is above the water level, you will also have a suction lift. The suction lift is limited to the pump NPSH or net positive suction head. The manufacturer of the pump will be able to provide with the NPSH of the pump since it is caracteristical of each pump.

Pump Drivers

There are many different types of drivers in irrigation systems. It also depends on the current availability where the system will be located. Pumps in irrigation systems can be driven by electric motors, solar panels, engines, or turbines. In order to determine the power necessary for the water to move along the pump (Water Horse Power or WHP) is calculated by multiplying the flow requirements (Q) times the total dynamic head or TDH, and dividing it by 3960. Please keep in mind that the WHP will be in optimus condition; therefore the actual power for the pump will be higher than this value. To calculate the actual value need or brake horse power (BHP) you will need to dived the WHP by the multiplication of the pump efficiency times the driver efficiency.  Please notes that both efficiencies (The Pump and the driver) can be obtained from the manufacturers.