The Irrigation Association has promoted July as Smart Irrigation Month since 2005. This is an effort to highlight water conservation and healthy landscapes through sound irrigation practices that embrace advances in technology. We’ve connected with Dave Shane, Central’s Commercial Irrigation Sales Manager, to learn more.
From: Dave
Having spent a few decades in the industry, I’ve had the opportunity to observe, design, troubleshoot, and offer recommendations on thousands of irrigation systems—from a one-zone research plot to massive and complex citywide systems that expand and change over many years.
Here are seven common problems and conditions I’ve observed over the years that did not embrace the latest smart irrigation technology available at the time, and very simple recommendations on how to avoid these pitfalls in the future.
1. Irrigation products working at improper pressure
This is the most common problem I see on site visits. Manufacturers publish a performance chart for their emission devices: rotors, sprays, drip, bubblers. The charts show several pressure settings for the various nozzles. The pressure settings are dynamic pressure at the inlet of the product. The design process ensures the correct dynamic pressure is delivered to that location. If the dynamic pressure turns out to be too high or low, the system is much less efficient.
High dynamic pressure causes misting and fogging, resulting in reduced throw. Low pressure also causes reduced throw and is obvious by a “rope of water” from the nozzle that delivers most of the water at the end of the reduced radius with virtually no coverage close to the head. The natural tendency in both cases is to run the zone longer to make up for dry spots. The result is water waste, longer runtimes, and less usable landscape areas.
Sometimes the pressure was adequate when the system was installed but changed later for a variety of reasons beyond the control of the designer or installer.
The only reasonable cure for low pressure is a booster pump. I’ve seen projects where nozzles are changed to a smaller size instead. This decrease in flow will lower friction loss and pressure drop but does not create pressure. It also shortens the radius, resulting in stretched spacing and inefficiency.
The cure for high pressure is regulation. Pressure regulation can be done at the source with an in-line regulator or at the master valve by installing a regulator made specifically for that valve. Regulators can also be installed on the zone valves. Another option is to use pressure regulating sprays or rotors. Regulation as close as possible to the nozzle is always the most efficient method.
2. Using the same nozzle in all rotors on a zone
This works if all the rotors have the same arc – quarter, half, full, etc. Generally, though, zones are a mixture of various arcs. If the quarter circle rotors use 1.5 GPM, the half circle rotors should use 3.0 GPM and the full circles 6.0 GPM. The design principle is that all heads should contribute relatively the same amount of water to a given area in the zone.
This design principle is called matched precipitation rate, or MPR. The issue with using MPR in rotor design is that, unlike spray nozzles, the larger the rotor nozzle, the further it will throw water. This makes it difficult to design head-to-head coverage without diffusing the nozzle or stretching the spacing. Both practices result in less than uniform coverage.
Most manufacturers now offer MPR nozzles for intermediate rotors but not for large rotors. Be a smart irrigator and use MPR rotor nozzles when possible. The coverage will be more uniform with shorter runtimes, water saving and healthier plant material. For large rotors applications, it is still best to use the same nozzle and zone by arc – half circles on separate zones from quarters, etc. and to use zone runtimes to even out application across the entire project.
3. Mismatched heads on the same zone
Irrigation products with different precipitation rates should never be installed in the same zone. When this rule is violated, some areas within the zone will invariably be too wet or too dry. Operators unsuccessfully try to compensate for this by changing runtimes. The result is water waste, longer runtimes, and less usable landscape areas.
Rotors typically have precipitation rates around .4 to .6 inches per hour (IPH), spray heads are around 1.5 to 2.0 IPH. Having both on the same zone is always bad news and must be avoided.
4. Stretched spacing between rotors or spray heads
Spacing should be no greater than head-to-head. This is referred to as 50% of diameter. Be somewhat skeptical of radius of throw details in the manufacturer performance charts. The radius is not where the very last droplet landed in a zero-wind test facility. The real-world radius is where the last effective droplets reach.
Manufacturers’ charts are always in zero-wind conditions because wind is infinitely variable in direction and speed. Real world wind conditions must be considered in design and installation. The Rain Bird landscape design manual has a commonsense write-up on spacing in windy conditions. It recommends spacing as close as 40% of diameter for wind up to 12 MPH. In this case, a rotor that effectively throws 30’ should be spaced at 24’. See page 41 of the manual at: Rain Bird Landscape Irrigation Design Manual.
When spacing is stretched, efficiency goes down and runtimes are increased to adequately irrigate the driest areas. The wettest areas get too wet, too much water is used, and plant health suffers.
5. Systems are overwatered and runtimes are seldom changed
Overwatering and seldom changing runtimes are common problems today despite the availability of smart controllers and increased awareness of plant water requirements. How often have we heard of spray zones running for ten minutes and rotor zones running for twenty minutes every day?
Consider using soil moisture sensors to control irrigation cycles. They work differently, depending on the specific sensor and controller. Some are like a rain sensor, stopping the irrigation cycle when a moisture level is reached. They controllers do not leave a record of moisture over time or even when irrigation stopped. Others are more sophisticated and can start the cycle when a low moisture level is reached. They provide an ongoing record of moisture levels over time.
Determining the quantity of sensors and their locations is critical to success. One sensor can control several zones or programs if their soil, plant material and exposures are similar. Always read the manufacturer’s installation recommendations or consult your Central Turf expert for assistance.
Consider using smart controllers. These controllers access cloud-based programs and can change runtimes based on very local weather conditions. They take away the guesswork and the need to go to the controller to make manual changes.
6. Improperly installed or missing rain sensor
Nothing dings our industry like systems running in the rain. A rain sensor is the least expensive and simplest smart product available. Unfortunately, they are often not used unless mandated by state or local law. I see sensors installed where rain cannot reach them, hanging loose at odd angles, with wires disconnected or located where access for service and testing is difficult.
7. No way to shut down systems for broken pipe
Broken pipe is a chronic problem, and one that is simple to fix. Install controllers that use flow sensors to compare actual to expected GPM. These controllers are smart enough to find an excess or low flow condition in either the mainline or a lateral. When used with a master valve or pump start relay, they can close the water source for excess mainline flow.
Standalone controllers with this capability have been on the market since the early 2000s yet are still not commonplace in commercial systems. They are now available and cost-effective for residential applications.
Finally, let’s truly make July Smart Irrigation Month by creating more efficient, more intelligent irrigation systems, from the nozzle to the controller. Better yet, let’s all resolve to create Smart Irrigation Year and Smart Irrigation Decade for a more prosperous industry as regulation-free as possible. If you have questions, reach out to your local Central rep. We’re here to help you grow!
About Dave Shane
Dave has more than three decades of experience in the irrigation industry in both distribution and manufacturing roles. He specializing in commercial project solutions with an emphasis on controls to meet complex requirements. He is an excellent resource for any technical questions about irrigation systems and finding the right solutions for efficient irrigation systems.