Senninger Irrigation


Different soil types respond differently to water. When it comes to irrigation, application rate must match your soil’s ability to absorb water. High application rates can create surface sealing and runoff, carrying surface soil away. Applying the water at a rate that matches the soil’s needs allows the water to penetrate the soil slowly.

Application intensity (the kinetic energy of the instantaneous water application) is also a consideration. High application intensity can damage your soil surface and alter the soil structure. This can damage its ability to absorb water for future irrigation applications. Lower application intensity is gentler. Applying the flow over a larger area reduces the application intensity.

Matching droplet size to the soil is yet another consideration. Don’t assume that smaller droplets are better. They are more prone to wind drift, lower uniformity, and higher evaporative loss. The optimum droplet size is the largest one possible that does not have adverse effects on the soil or the crop.

Within healthy soil, different-sized particles are arranged allowing good infiltration. High application intensity breaks down the soil structure and disrupts this delicate balance. As infiltration begins, particles become segregated by size. The smaller particles become suspended and the larger clods dissolve. The water flows quickly through the soil below, filling in the open areas causing compaction. The smaller particles that had been suspended now rest on top of the soil, creating a sealing effect. This newly arranged soil structure prohibits future water applications from penetrating properly. The result is surface water buildup and runoff.

What is the Real Bottom Line?

No comments

When you think about the bottom line of your irrigation system, many questions come to mind. What is the cost to install the system? Where can I save money? When will I see a return on my investment? However, these are just the initial costs. Many people think this is the bottom line and don’t see the bigger picture of how small savings up front might impact your energy costs, loss of water, soil damage, and your yield.

Low pressure systems save energy costs. Pressure fluctuations effect sprinkler flow, droplet size, and wetted diameter. In a 10 psi applicator, a variation of 1 psi can mean a 5% difference in flow which causes the over- and under-watering of unregulated systems. The use of in-line pressure regulators helps maintain consistent outlet pressure regardless of variations.

You should select applicators specifically designed for low pressure operation.  Base the decision on performance and not price. Look closely at their application rates – average and instantaneous. Average Application Rate (AAR) is the rate of water applied over the entire wetted area. This average value assumes uniformity in the wetted area is constant. AAR is calculated by multiplying the system’s flow by 96.3 and dividing that by the area irrigated. Instantaneous Application Rate (IAR) is the rate of water application at an instant in time, not the total water application. Sprinkler packages must be carefully designed to keep IAR below average soil intake rate.


Instantaneous application of stream driven applicators – flow is delivered to a relatively small area.


Instantaneous application of wobbling devices – flow is spread out over a large area.


Pattern integrity – the consistency of the distribution footprint from an applicator – is also important. This requires maintaining the size of the irrigated area as well as the uniformity within that area. Applicators must deliver the “right sized” droplets. The “right size” is the largest droplet possible that does not have adverse effects on soil or crop. Larger droplets resist wind and travel farther, providing a larger diameter of coverage. If they are too large, they can have a negative effect on the soil or crop. Smaller droplets are gentle on the soil and crop, but must not be so small that they are prone to wind drift or evaporation.

There are so many sprinkler choices to consider. Today, software is available to analyze various performance specifics before you buy to assure you have a design that meets the requirements for your specific installation. When done correctly, system design produces success at harvest, increasing your crop yield.

With these new analytic technologies comes the responsibility to use our resources wisely. Water and energy savings are not only desirable, but mandatory. The focus on the initial cost of installation is no longer the “bottom line”. The real “bottom line” is in what can be saved – water, energy, soil quality – added to your increased crop yield from proper system design.

For more information about irrigation products that save water and energy, contact Senninger Irrigation at or visit

In this chart, look at 40 psi as an example. Normal hysteresis is between the top blue line showing increasing pressure and the second blue line showing decreasing pressure. The top line is 10.25 and the second is 9.75 making the hysteresis 0.5 psi.

HYSTERESIS in pressure regulators is the difference in outlet pressures when the inlet pressure is increasing to a certain psi above the regulating pressure, and then decreasing to that same psi. It can vary depending upon the flow and the outlet psi where the measurement is taken.

Hysteresis is caused by any force resisting the free movement of the throttling stem within the regulator other than that of the spring or outlet water pressure acting on the total effective diaphragm area. Such forces could be friction at the o-ring/throttling stem seal and the rolling resistance of the diaphragm.

Low hysteresis is important for accurate regulation, especially with varying inlet pressure.

FRICTION LOSS is what makes a regulator work. While it is not good before the point of regulation, it is essential after it starts to regulate. We rate our regulators at the flow that causes 4 psi loss through a fully open regulator. If you have 50 psi into a 20 psi regulator, that 30 psi difference is the friction loss caused by the throttling stem closing against the seat, plus the friction loss of the fully opened regulator at that flow.

Our pressure regulators should have 5 psi more into them than is expected out. Other regulators require more inlet pressure to achieve proper regulation.

ACCURACY of our pressure regulators is +or – 6% of the design pressure for a particular flow as shown on our performance charts. Accuracy is important to assure optimum irrigation system performance.If the outlet pressure of our 20 psi PSR regulators is 20.5 psi at 5 gpm, then it will regulate between 21.73 and 19.27 psi (+6% and -6% of 20.5 psi).

Senninger introduced the first quality in-line pressure regulator to the irrigation industry in 1966. Our regulators are 100% water-tested for accuracy and have a two-year warranty on materials, workmanship, and performance.

For more information about pressure regulators, contact Senninger Irrigation at or visit

How a Wobbler Works

No comments

Wobbler’s wetted footprint

Senninger introduced the Wobbler in 1980. The technology of this sprinkler design provides outstanding uniformity at low pressure, making it very popular for water and energy savings. The key to Wobbler technology is the off-center rotary motion and unique groove configuration of the water deflector.

The grooves in the deflector divide the flow into numerous sections of water.The off-center wobble further divides each section into relatively uniform-sized droplets. The rotary action evenly distributes these droplets over a large area. Water distribution occurs very rapidly. There is no waiting for the sprinkler to make a complete revolution to fill in the distribution pattern. This instantaneous coverage is gentler than stream driven devices and helps preserve soil absorption.

Grooves in the deflector divide water into gentle droplets

Droplet size is determined by the deflector’s specific groove configuration and angle. Several deflector models are available. Wobbler technology is available for mechanical move/pivot systems (i-Wob and Xi-Wob), and for nursery/greenhouse/sold set applications (mini-Wobbler, i-mini-Wobbler, Wobbler, and Xcel-Wobbler).

For example, consider our i-Wob SA9 model. It has 9 grooves in its deflector. With a #24 nozzle at 20 psi (1.38 bar), the deflectorspeed is 100 rpm. There are 25 “wobbles” for each revolution. 9 streams of water x 100 rpm x 25 wobbles per revolution produces 22,500 discreet streams of water per minute. The wobble continues to divide these streams into millions of droplets for gentle, uniform rainfall over a large area. This produces a uniform water pattern at low pressure.

What Droplet Size is Best?

No comments

Large, medium and small droplets impacting the surface of water.

Sprinkler manufacturers do not publish the actual droplet dimensions. This would be difficult to measure and would not address what that size really means. Instead, they provide more general droplet information – small, medium, large.

Tighter soils require smaller droplets because they have a lower kinetic energy. However, smaller droplets are susceptible to wind drift, evaporation, and distortion of their distribution pattern. Their overall mass prevents them from traveling far, producing a smaller diameter of coverage, therefore needing closer sprinkler spacing.

Looser soils can accept larger droplets which have a higher kinetic energy. Larger droplets are less likely to be impacted by wind, helping to retain their distribution pattern. They provide a greater distance of throw, producing a larger diameter of coverage, allowing for wider sprinkler spacing.

Flow, pressure, and the deflector configuration determine droplet size. Some sprinklers produce a mixture of small and large droplets. However, this does not prevent soil damage or distortion of the distribution pattern. If a sprinkler produces droplets which are relatively uniform in size, you can select droplets that are suitable for your soil and adequate in size to resist wind distortion. This will help maintain their distribution pattern integrity, thus improving irrigation efficiency and conserving water.

Small droplets are easily affected by wind and their distribution pattern can be distorted.

Larger consistent-sized droplets are less susceptible to wind and help retain their distribution pattern.

For more information about applicators that produce consistent sized droplets, contact Senninger Irrigation at

Low Pressure Irrigation Saves Energy

No comments

Low pressure irrigation translates to reduced horsepower requirements and reduced energy consumption. With rising fuel and electricity costs, low operating pressures offer you a tremendous opportunity to lower total pumping costs. The savings vary depending on your specific system. Hours of operation, flow, pressure, energy source, and cost are all considerations. We at Senninger have a tool available that can provide you with a snapshot of the possible savings based on these considerations. It can be found as a link on our homepage to the Energy Calculator (screenshot shown here).

The Energy Calculator is a tool available online to show you possible energy savings.

If you try to use your older applicators designed for higher pressures at lower pressure, they will produce distorted distribution patterns. They will also deliver droplets that are too large and can have an adverse impact on the soil surface.

Before you select new applicators, you should be sure that they are specifically designed for low pressure operation. If not, they will not provide you with optimum performance. The criteria for low pressure may vary from one manufacturer to another. Typically, low pressure is 20 psi or less. Anything over that is really more of a mid-range applicator.

If applicators are designed for low pressure, they should not be used with high pressures. Otherwise, they can produce water droplets that are susceptible to evaporation and wind drift. For optimum performance, it is best for you to use the manufacturer’s guidelines.

For more information about low pressure applicators and their energy savings, contact Senninger Irrigation at or visit

A sprinkler profile illustrates where water falls in relation to the sprinkler. This is based on flow, pressure, and height. A denso-gram illustrates the distribution uniformity from this information based on spacing.

A single applicator’s uniformity is only part of the picture. The effect of overlapping applicator footprints or, in the case of mechanical move systems, the movement of the applicator, shows the overall distribution uniformity for specific sprinkler spacing. The application rate of these overlapping sprinklers can be tailored to your soil and crop needs. This information is based on no wind perfect world conditions. Actual field performance will vary.

Consider some of the things that impact the uniformity in the real world. Changes in field elevation cause pressure fluctuations. Zones or pivot end guns cycling on and off change pressure. These all alter the flow which impacts the sprinkler uniformity. The use of preset pressure regulators is ideal to overcome these changes to maintain distribution uniformity.

Test the application uniformity of sprinkler layouts before your system is installed. Compares different spacing, sprinkler models, nozzle sizes, and operating pressures to determine which would be best for your specific application.

This image is from our WinSIPP2 software. These terms are used in the image shown:

  • Coefficient of Uniformity (CU): developed before computers, calculates uniformity mathematically. However, it views over- and under-watered areas equally. It doesn’t tell how bad a particular area might be.
  • Distribution Uniformity (DU) looks at over- and under-watered areas differently. It sorts and ranks all data points in the overlap area and uses shading to graphically display it as a denso-gram. The wettest area is darkest and the driest is white. All other wetted values fall between with corresponding shaded values.
  • Scheduling Coefficient (SC), developed by CIT (Center for Irrigation Technology) provides a way to measure uniformity. It uses a sliding window to analyze sections of the sprinkler pattern. It calculates the ratio of lowest and highest values to determine the run time of the application needed to water the driest areas. An SC close to 1 is good.
  • Application Rate is the amount of water applied. This is often shown in inches per hour. This must match your soil’s intake rate. 

For more information about sprinkler uniformity, contact Senninger Irrigation at or visit

How Does a Pressure Regulator Work?


A pressure regulator limits excess inlet water pressure to a constant outlet pressure. You need constant outlet pressure to ensure that your sprinkler (or emitter) performs well.

Water travels through the inlet end of the regulator and around a fixed seat into the critical flow area. The water then enters into a hollow cylinder called a throttling stem (or T-stem) which is attached to a larger diaphragm near the outlet end. A spring around the throttling stem tends to hold the flow area open, while water pressure acting on the total diaphragm area tries to close it. This duel always ends in a draw with the outlet (or regulated) pressure being determined by the spring’s compressive strength.

What does this mean to you?

Your sprinklers can only pass along what they receive. Give them consistency and they’ll return the favor. Most sprinklers perform best at a specific pressure level, often lower than your in-line pressure. But in-line pressure should be at least 5 psi (0.34 bar) higher than your regulator’s designed outlet pressure.

A regulator’s design and the materials used to manufacture it greatly impact its accuracy. Be sure to choose the regulator model that best fits the flow and pressure required for your application.

Senninger introduced the first quality in-line pressure regulator to the irrigation industry in 1966. Our regulators are 100% water-tested for accuracy and have a two-year warranty on materials, workmanship, and performance.

For more information about pressure regulators, contact Senninger Irrigation at or visit

LEPA (Low Energy Precise Application) irrigation was developed in the early 1980’s. It was to meet the needs of the declining aquifer levels in the western high plains of the United States. Today, LEPA continues to deliver significant water and energy savings worldwide.

In true LEPA systems, applicators are positioned to deposit water into every other furrow. This requires planting in circles for center pivots and straight rows for linear machines. Heat accumulates in the dry areas and keeps the plant warmer. The plants share the water in the furrow in between. This keeps the crop canopy dry and prevents possible damage from salt in the water. Because water application is close to the soil, LEPA is 95% efficient in water use and requires very low pressure – 6 to 10 psi (0.41 to 0.69 bar). This saves energy and conserves water.

LEPA systems must include furrow dikes or crop residue to hold water in the rows near the plant until the soil can absorb it. LEPA irrigation works best on farms with a flat terrain and relatively sandy or loamy soil where runoff is not as likely as in heavier, tighter soils or sloping terrains.

We introduced our Quad Spray in 1986 specifically for LEPA irrigation. This sprinkler provides four different ways to apply water based on crop need. A simple twist changes this applicator to deliver one of four modes: two different bubble modes that irrigate directly into the furrow, a spray mode for germination, or a chemigation mode to wash the underside of the crop canopy. Other LEPA products include our LDN with a bubbler pad or drag hose adapter, and our Super Spray with a drag hose adapter.

  • Drip vs Overhead Irrigation (Part 5) Originally published in Growing Magazine’s July 2014 issue. Minimal investments for a strong ROI For large-scale commercial growers, overhead irrigation is more economically feasible. Drip systems typically cost $500 to $1,200 or more ... Learn more »
  • Drip vs Overhead Irrigation (Part 4) Originally published in Growing Magazine’s July 2014 issue. Less Complicated Farm Management at a Lower Cost After switching to drip irrigation, growers initially use less water, save money and get similar yields ... Learn more »

Senninger Irrigation

Senninger Irrigation
A Hunter Industries Company
16220 East Highway 50
Clermont, FL 34711

Office: (407) 877-5655

Site Credits: Z to A Creative

STAY CONNECTED:   Senninger Irrigation  Senninger Irrigation
Senninger Irrigation