The right irrigation pump comes down to three things: where your water is coming from, how much flow the system needs and what power is available on site.
Not every irrigation system needs a pump. Systems connected directly to municipal supply with adequate pressure may not. But systems drawing from surface water, wells, storage tanks or sites where supply pressure is insufficient to operate the zones, a pump is the core of the system. Choosing the wrong one leads to inadequate coverage, excessive wear and early failure.
The Three Main Pump Types
Centrifugal pumps use a rotating impeller to add velocity to water, which is then converted to flow pressure. They are the standard choice for drawing from lakes, ponds, streams and shallow wells. Centrifugal pumps must be primed, or filled with water, before operation. Running dry damages the impeller.
Jet pumps operate on the Venturi principle: water moving through a constricted nozzle creates a pressure drop that draws additional water into the flow. Jet pumps are used in low-flow applications, perform well in warm climates with high water tables and can be configured for shallow or deep well installations.
Submersible pumps are sealed units that operate fully submerged. The motor and pump assembly are positioned below the water surface. The motor sits below the pump body, and water is drawn in through a screen between them. Submersibles are used in deep wells and cisterns where the pump cannot be located above the water source.
Sizing the Pump: GPM and PSI
Two figures determine pump size: GPM (gallons per minute) and PSI (pounds per square inch).
GPM requirement is calculated by multiplying the number of heads in the largest zone by the per-head GPM listed in the manufacturer's specifications. The largest zone sets the sizing floor. The pump must be able to supply that zone at full flow.
PSI requirement is the operating pressure the heads need to function correctly. With both figures established, the pump can be matched to a performance curve that confirms it will deliver adequate flow and pressure simultaneously. See the pump curve reading guide for the full sizing process.
Power and Water Source Considerations
Confirm the available power supply at the pump location before specifying. Standard relay contactors accommodate 110V to 220V for pumps ranging from 3/4 to 3 horsepower. Pumps larger than 3 horsepower require different contactor and overload protection configurations.
Water source affects pump selection in several ways. City water supplies carry incoming pressure that the pump boosts to the required operating level. Surface water sources at a distance require accounting for friction loss in the supply line — longer runs to reduce effective pressure at the pump inlet and may require a higher-output pump to compensate. Water with significant sediment or debris content requires filtration before the pump to prevent impeller damage. Filtration adds to friction loss, which must be factored into pressure calculations.
Pump Control and Protection
A pump control box manages start/stop signals from the irrigation controller and protects the pump from conditions that can cause damage. Basic systems use a pump start relay, an electrical device that translates the low-voltage signal from the controller into the power needed to activate the pump. Pump start relays should be installed at least 15 feet from the controller and pump to prevent electrical interference.
For systems where pump protection matters — and it should in any installation where a dry-run or overtemperature event could damage a significant investment — control boxes with integrated pressure and temperature sensors are available. These cut power to the pump automatically if a monitored condition exceeds safe limits.
Backflow prevention is required on any pump-fed system connected to a potable water supply. The pump's ability to generate pressure above supply pressure creates a back-pressure condition that can drive irrigation water into the drinking water line if no mechanical barrier is in place.
