By Erik Skindrud, regional editor

Irrigation controllers use computer memory and weather data to calculate water needs much more precisely than timer-based automated controllers can.

The technology has been incorporated into control units sold by all of the major manufacturers. Each brand uses different methods and displays, and all make competing claims for their effectiveness. It can be difficult to evaluate those claims, of course, unless you have access to your own university testing facility.

In April, LSMP looked at eight advanced controllers (“Smart Irrigation Controllers: An Overview”) and quoted a study conducted by the Metropolitan Water District of Southern California, which evaluated three of them.

Reader Dennis R. Pittenger of U.C. Riverside’s Dept. of Botany and Plant Science saw the article and thought of another controller study he co-published last year. While it looks at four older models, the portion reprinted here can serve as a guide for groundskeepers and others looking to purchase irrigation controllers. Superintendents and other maintenance professionals can do their own research before purchasing a system. Company web sites are good resources for comparison data.

Finally, carefully reading instructions will help ensure that each unit is used as effectively as it was designed to be used.

“These new devices are potentially great landscape irrigation management tools,” Pittenger told LSMP. “But there has been little objective evaluation of their performance. At this point in time, prospective users should evaluate these devices carefully and understand some of their limitations.”

A summary of the University of California report is reprinted below. The entire document can be found online through a link (“Evaluation of Weather-sensing Irrigation Controllers”) listed at the bottom of Pittenger’s web page: https://plantbiology.ucr.edu/people/?Pittenger&show_for=new_window

Study Results

Aqua Conserve was the simplest, easiest to operate, and most appropriate for homeowner use of those products studied. It applied water at the correct frequency and irrigated trees/shrubs with reasonably good precision, but it tended to apply more water than needed to all landscape treatments, especially in the summer for cool-season turfgrass.

The study called the Aqua Conserve unit "the simplest, easiest to operate" controller reviewed. The company's ET-16 works with an optional temperature sensor to fine-tune historical climate data. Photo: Aqua Conserve

Calsense ET1 with an electronic ET gauge input offered the most complex interface, and it was equally as complex to set up. Since the electrical connections and function of the electronic ET gauge repeatedly failed in our study, it was impossible to evaluate fairly its weather-based irrigation scheduling capabilities.

The Calsense controller "offered the most complex interface," the study authors wrote. This ET2000 is more advanced than the ET1 evaluated in the study, and has an optional wind sensor that can halt irrigation during windy conditions. Photo: Calsense

WeatherSet was simple and easy to use but visually intimidating. It produced very inaccurate irrigation schedules that would have damaged plants due to severe under-irrigation.

A mini weather station works with Weatherset's Outdoor ET Controller to calculate on-site irrigation requirements. The study authors found the Weatherset product "simple and easy to use." Photo: Weatherset

WeatherTRAK was the most sophisticated controller studied and the most flexible in addressing the specific parameters found in each landscape setting, but it requires a professional landscape manager (or equivalently trained individual) to set up the unit accurately. It provided relatively accurate irrigation schedules for cool-season grass, but grossly over-watered the trees/shrubs treatment.

WeatherTrak "was the most sophisticated controller studied and the most flexible," the authors reported. The system uses data including slope angle, soil and plant type in addition to temperature, wind and humidity to calculate local water needs. Photo: HydroPoint Data Systems, Inc.