Facilities with heavy water needs—such as farms, golf courses, and commercial green spaces—spend a large portion of their energy usage on irrigation, particularly for operating the pumps that their processes rely on. For example, pumping water can be as much as 30% of a farm’s total energy use.

Prioritize system maintenance At the beginning of each season, check your irrigation system to make sure it’s performing optimally. Keep your pumps serviced and well-tuned, and keep electric motors, switches, and control panels free of dirt, insects, and bird nests. Check connections for tightness and lubricate moving parts as needed. Check for correct motor impeller alignment, worn nozzles and shaft sleeves, leaking gaskets and drains, and dried-out pump packing and bearings. At season’s end, thoroughly clean and lubricate components to prevent deterioration during periods of dormancy.

Optimize pump operation You can find significant energy savings by optimizing the way your pumps and irrigation equipment work. We discuss all of these options and more in our Managing Energy Costs in Agriculture topic, but we’ve collected some of the most effective options here.

  • Test your well pumps; aim for 60% efficiency
  • Upgrade to premium-efficiency motors, particularly if repair costs would exceed 65% of replacement cost
  • Install variable-frequency drives to reduce energy use when flow rates are low and allow the pump to start and stop more slowly
  • Consider replacing aging pump components such as shaft sleeves, wear rings, packing, and impellers
  • Ensure your system fittings are appropriate for system usage
  • Take advantage of surface-water sources, and ensure that both suction and discharge systems are operating efficiently

What are the options?

Almost all irrigation runs on centrifugal pumps, which use impellers to spin the water in a housing, moving the water via centrifugal force. If a centrifugal pump has more than one impeller and casing setup, it’s referred to as a multistage pump, with pressure increasing each time the water passes through an impeller-casing pair. Centrifugal pumps cannot pull any air, only water, and must be primed by filling both the pipe and casing with water before starting the pump. Most centrifugal pumps can hold water via a valve so that you don’t need to prime the pump after the first time.

End-suction centrifugal pumps End-suction pumps are best suited for smaller volumes of water. These pumps are close-coupled to the electric motor, so that the pump itself is mounted on the motor’s drive shaft and the pump case is bolted on so that the pump and motor look like a single unit (Figure 1). This is why the terms “pump” and “motor” are often used interchangeably.

Figure 1: End-suction centrifugal pump diagram

End-suction pumps are much better at pushing water than pulling it. They’re best in applications that locate the pump at nearly the same height as the water source, such as surface-water scenarios. As a rule of thumb, make sure that the pump is not more than five feet above the water’s surface.
A diagram of an end-suction centrifugal pump showing the horizontal water intake path through the impeller and out again.

Almost all portable pumps are end-suction centrifugal pumps. This portability also results in them being great booster pumps for situations where the water pressure in an irrigation system is too low for sprinklers to operate.

Submersible pumps Submersible pumps operate completely underwater, with pump and motor making up a single unit (Figure 2). They can be a good choice if you have access to any sizable amount of standing or running water via wells, ponds, lakes, or streams.

Figure 2: Submersible pump diagram

Often submersible pumps are cylindrically shaped and housed inside a well casing so that debris from the well walls doesn’t foul the pump. Though most of these pumps are designed to operate vertically, many can also be laid horizontally on the bottom of a lake or stream.
A diagram of a submersible pump showing the vertical water intake path through the submerged pump and motor housing at the bottom, up a drop pipe, and out above ground.

Submersible pumps tend to be more efficient because they only push water, they don’t need to draw it in first. Because they are already underwater, they don’t need to be primed.

Turbine pumps A turbine pump is a centrifugal pump that’s mounted underwater and attached by a shaft to a motor mounted above the water (Figure 3). The shaft usually extends vertically down a large pipe. The water is pumped up this pipe and exits directly under the motor.

Figure 3: Turbine pump diagram

In a turbine pump, the motor and impeller aren’t housed in the same casing, but are connected via a long driveshaft.
A diagram of a turbine pump showing the vertical water intake path through the pump housing at the bottom, up a drop pipe, and out above ground. The motor is aboveground, separate from the pump.

Turbine pumps are efficient, and they’re a good fit for larger pump applications, such as farming. Often they consist of multiple stages; each stage is essentially another pump stacked on top of the previous one to form a chain that increases operating pressure.

How to make the best choice

Selecting the best pumps can be difficult. If you’re inexperienced or unfamiliar with pump selection, it can be well worth the time and expense to hire a professional to suggest options. Alternatively, if you know your irrigation system’s operating pressure (in either “head,” which is measured in feet, or pounds per square inch) and volume flow rate (gallons per minute), you can also contact a pump dealer, and they’ll be able to provide suggestions. Make sure to know your water supply laws and limitations, and be mindful of whether your water source is intermittent or if objects or debris end up causing blockages, since operating pumps without any water can cause damage.

Once you know the pressure and flow requirements of your system, research the available pump models and select one that meets your requirements. Manufacturers should be able to provide you with a performance curve for a specific pump (Figure 4). When reading this curve, keep in mind that there is a trade-off between pressure and flow: higher pressure means lower flow, and lower pressure means higher flow.

Figure 4: Example pump performance curve

Usually, a performance curve depicts performance of a specific pump model. The curved lines represent impeller diameters, and the straight lines represent motor horsepower (hp). When using this chart, start with the pressure you need (on the vertical axis), then move across the chart horizontally to the line that indicates the flow you require, in gallons per minute (gpm). Mark that point, then select the closest impeller size curve and horsepower line above your marked point to determine the horsepower and impeller size needed for your pump. For example, a pump at point A (100 head, 120 gpm) would require a 5 hp, 6-inch diameter pump, and point B (75 head, 80 gpm) would require a 3 hp, 5-inch diameter pump.
A line graph showing curved lines for pipe diameter and straight lines for pump horsepower

What’s on the horizon?

Pumps mainly improve when motor efficiency does. Alternating current (AC) induction motors have long been the industry workhorse, and they’ve benefited from incremental efficiency gains over the years. As efficiency standards continue to tighten, “super premium efficiency” motors may become mandatory. AC induction motors are near their technological limit and cannot reach these new standards without adding high-cost materials, so industry personnel will be looking to different motor types—such as permanent magnet motors or induction motors—to make further efficiency gains.

Who are the manufacturers?

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