Sensors At Work

Set any irrigation schedule you like on a controller, but if the controller doesn’t change with the environment, it’s nothing but a dumb timer. Worse than that, it’s a water waster. That’s why irrigation sensors, which feed controllers information about the environment, are such key players in water conservation today.

These monitors of soil moisture, rain, freeze, wind, ET, flow (and more), are guiding controllers to give precisely the amounts of water needed to keep plants healthy. They turn off the system at preset times, and then allow it to come back on when appropriate. It’s unnecessary to over-saturate the soil, leading to fungus, disease and pests. It’s unnecessary to water during a rainstorm, leading to angry taxpayers and high utility costs. And in freezing temperatures, it’s absolutely unsafe to waste water.

In some areas of the country, sensors are said to be saving more water than low-flow toilets and showerheads combined. Which brings us to a most interesting trend in water conservation affecting the irrigation industry today: an increasing number of municipalities throughout the country have mandates and cost-savings programs for the use of sensors, particularly rain sensors, on new and existing residential and commercial projects.

“These laws open a new profit center for contractors,” says Rich Ali, the director of state and affiliate relations for the Irrigation Association (IA). “It’s a whole new area for retrofitting systems, and also a way for a contractor to show that he cares about saving water. Because when it’s raining and systems are running, our industry gets a black eye.”

Sensors are very interesting these days because they’re being designed for wide use, from simple residential systems on up to top-of-the-line commercial ones. Plus, they’re easier than ever to install and maintain. Here’s a look at several key landscape irrigation sensors, along with some helpful tips.

Rain sensors
Useful in all but the most arid environments, rain sensors are by far the most widely used irrigation sensor today. Their water-savings ability, simple design, reliability, low cost and ease of installation have made them popular, especially with a growing number of legislators. Currently, there are mandates for rain-sensor use either statewide or in various municipalities in New Jersey, North and South Carolina, Florida, Texas, Minnesota and Connecticut (as of Oct. 1).

“The IA is addressing this issue aggressively, and there’s a good chance you’re going to see 80 percent of the states requiring rain sensors in the next five years,” says Ali.

The water savings are generally substantial, particularly in temperate climes with average rainfall. For an example of how to calculate water savings from rain sensors on your sites, check out Hunter Irrigation’s Mini-Clik rain sensor Web site, under “FAQs.” Then use the information you gather to market your services further.

“Through reduced water and labor costs, rain sensors will pay for themselves in one season,” says Jeff Carowitz, VP of marketing for Hunter.

Before installing these sensors, check the manufacturer-set adjustments for rainfall and drying rates. The rainfall settings should be adjusted to respond to the site’s particular needs. Also, the sensor’s drying ring controls the airflow over the disks and the rate at which they dry out (thus retriggering the system). Carowitz recommends that you set this ring so that it matches the drying rate of the site’s soil.

When installing these sensors, make sure they are exposed to normal rainfall.

“I don’t know how many times I’ve seen sensors installed under a tree,” says Dave Klever, president of Ecologic, Inc., maker of the RainBrain rain sensor. “When you look up from the sensor, all you should see is sky.”

Once the sensor is adjusted and installed correctly, there’s no reason why you can’t set it and forget it, according to Susan Basch, product manager for Rain Bird, which makes the RSD Series rain sensor.

“This is less true with other sensors, but there’s a trend in that direction for those as well,” she says. “Homeowners don’t want to be checking their sensor, and if the contractor doesn’t have to go back and adjust something, that’s money in his pocket. Manufacturers are putting it upon themselves to try to make something that takes very little maintenance.”

A great trend in rain sensors are radio-controlled, or wireless, which make installation easy. These sensors have a receiver unit installed next to the controller, and a sensor unit out in the landscape.

“You can add a wireless sensor to any irrigation system with an auto timer in about 15 minutes time, at a unit cost of less than $100,” says Carowitz. “So, homeowners can easily retrofit their system.”

“Wireless rain sensors provide an advanced level of irrigation management,” commented Mike LaHiff, marketing manager of R&D Engineering, Manasquan, New Jersey, the company that introduced the wireless rain sensor. “Some of the new, advanced features of wireless rain sensors include: visual display of sensor status, intelligence to prevent unnecessary watering even after a power outage, bypass controls with automatic reset, and easily replaceable batteries.”

“In addition to simplified installation, wireless rain sensors offer an almost limitless choice of mounting locations,” says LaHiff.

Another great new feature with sensors is instant shut-off. Instead of taking several minutes to absorb enough water to swell up and turn off the controller, these sensors instantly detect rainfall and turn off the system immediately.

Soil moisture sensors
The great thing about the various soil moisture sensors is that they are by nature highly accurate tools, offering information that is very specific to the soil and plant material. Installed directly into the soil, where they constantly measure soil-moisture status, they allow the controller to open the valves as programmed only after the soil moisture has been allowed to deplete to the level where irrigation is needed.

Soil moisture sensors can match water application rates from 40 percent up to an average of 80 percent of theoretical ET, according to Tom Penning, president of Irrometer Company, which made the first soil moisture sensor (an improved tensiometer) for the landscape market in the 1960s. Many of the sensors out today are basically improved tensiometers and gypsum blocks, updated with solid-state circuitry, handheld meters and adjustable modules, such as Irrometer’s Watermark sensor.

“One great benefit of soil moisture sensors is that you can encourage deeper plant root growth so that the plants become more drought tolerant and healthier,” says Penning. “This is particularly great for trees.”

Despite such positive results, soil moisture sensors have gotten a reputation for being unreliable and requiring a great deal of maintenance. Numerous field studies document these contractor concerns as unfounded, particularly in light of the well-designed and built sensors now on the market, but contractors still have shied away.

“But today, with all the newer technology available, soil moisture sensing is being resurrected as a plausible water-savings tool,” says David Byma, president of Calsense, which offers the ET2000 field controller with ET and moisture sensing. “It’s because more storage, ease of use and information processing has become possible and at cost points that are much more affordable.”

Another technology, capacitance, is used in the Moisture Sensor and Irrigation Control System offered by H2O Strategies, Inc. “Our customers typically report savings in both water and power, along with improved landscape quality as problems associated with over-irrigation are resolved,” says Kathleen Hellmers, president of H2O Strategies. She added, “Because moisture sensors determine the actual amount of water at their placement depth, it is fair to say that they provide the user with what we call ‘true ET’.”

Soil moisture sensors are more technical than rain sensors, and they require contractors to become educated on how to use them properly and how to schedule the system to get the benefits from them, according to Penning. However, manufacturers are offering failsafe ways for easier, accurate set-up. Some offer software that guides you through site water audits, others offer software that allows you to easily fix any mistakes, such as assigning the wrong valve to a sensor, via software to the controller. Plus, tweaking the sensors is easy via user-friendly moisture readouts.

Hooking up the sensors is no more difficult than wiring a valve, according to Penning, who recommends that they be installed in all zones on large sites. However, on a typical residential, with six valves for instance, a single sensor need only be installed in the driest area, typically the turf areas with the highest sun exposure. The other zones are then adjusted in respect to this driest area.

“Judging soil moisture off one zone on a smaller residence is easy and works well for water savings and efficiency,” says Penning.

Flow Sensors
Flow sensors are another exciting area of growth in the irrigation sensor market, particularly for regions of the country where water is scarce.

“This is one of those technologies that has been historically valuable for central control and larger sites,” says Basch. “There’s growing demand for it on smaller sites, and manufacturers are listening. They’re taking all that technology and boiling it down.

“Unfortunately, I don’t know whether the benefits of flow sensing are well understood,” she says. “The most important benefit is the intelligent use of water because flow sensing, properly implemented, allows you to identify broken sprinklers and broken valves.”

Flow sensors monitor for over-flow situations and the damage that can occur if left undetected. If a sprinkler head breaks or a pipe ruptures, these sensors bring an irrigation system to a halt, either a zone or the entire system.

Flow sensors are installed inside the mainline piping that provides water to the system control valves. The exciting thing is that some companies, such as Hunter and Data Industrial, make sensors with interface devices that will take information from the flow sensors and convert it to a signal that will work with all the different brands of standard controllers.

“Flow sensors today can be an easy system upgrade for a large or small site where you just tap it into the system’s mainline, install it in the valve box and wire it in just like any other sensor into the system, and it works with any controller,” says Carowitz. “It’s a huge trend right now.”

ET Gauges
To take a controller to the next level of high-tech automation, with up-to-the-minute real-time adjustments, you’ll want to install either an ET gauge, ET tracker, solar radiation or temperature sensors to your ET-based or ET-compatible controller. Each manufacturer has a different twist on which environmental factor is measured and how, be it solar radiation, temperature or actual ET, but any one of the sensors will keep you in the efficient water management game. These devices automatically modify the watering schedule, based on one of those environmental conditions.

“The idea is to feed the weather information back into the system, so that the controllers themselves can automatically adjust to daily climatic changes,” says Byma. “Because you’re doing it automatically through the computer and controller, it’s very inexpensive to do; the savings become very real.”

Depending on the controller, the sensor can either completely take over the schedule adjustments permanently or, during extreme conditions, temporarily override the schedule with the built-in ET data acting as a short-term backup schedule. Keep in mind that some (but not all) sensors are proprietary, meaning that they only work with the same manufacturer’s ET controller.

“ET is a good baseline measure of how well you’re irrigating, and you see municipalities, particularly in California, using ET as their baseline number for evaluating water use,” says Basch. “It’s a concept that’s well understood, and now there’s an interest in seeing it making its way down to the lower price points.”

There’s also an interest in combining ET info and soil moisture sensing, according to Byma. Manufacturers are offering controllers that will let you irrigate based on weather conditions plus moisture sensing.

“Several agronomists have told us that there’s a 10 to 15 percent savings on top of the ET savings, when you add moisture sensing,” says Byma.

Freeze Sensors
“Freeze protection is an up-and-coming issue in areas where people leave their sprinklers on year-round, especially in the regions along the sunbelt,” says Ecologic’s Klever.

Contractors in climates without a definitive seasonal transition find freeze sensors a good way to temporarily stop irrigation rather than shutting off the system completely. This way they can avoid the liability issues of ice-laden walkways and streets caused by landscape irrigation water freezing.

For these climates, wireless rain sensors with built-in freeze sensors are the ideal solution. “Contractors enjoy the ease of installing one wireless unit, while providing the end user with both freeze and rain protection,” says LaHiff.

A great trend with freeze sensors is that they are being offered as an optional feature on rain sensors, as well as wind sensors. The rain sensor basically has a thermostat that activates the sensor at a certain pre-set temperature.

Wind Sensors
Wind sensors are useful in areas with sporadic high winds that can cause poor irrigation coverage or overspray. Rather than irrigate when most of the sprinkler’s spray or stream pattern would be carried away by the wind, this sensor shuts down irrigation when the wind exceeds a certain velocity depending on a preset determination, then it allows irrigation to restart once the wind stops.

Wind sensors are also extremely useful with fountains in a windy area, to keep water from gusting onto buildings and pedestrians, or if a system is watering a landscape near a glass building that can become spotted.

“It’s a great time for sensors, as the industry keeps heading toward embracing more technology to try to make the people’s jobs easier,” says Byma. “We want to help contractors achieve as much water and labor savings as possible.”

According to Mike Miller, manager of Baseline, LLC., soil moisture sensing controllers are now a reality. “The cost of reliable sensing technology is now within the reach of all commercial and residential customers. These systems can actually allow landscapes to water themselves, calling for water when needed and shutting off the water when enough has been applied.”

Miller admits, “There’s still a lot of resistance among contractors,” but adds that advanced technology will be the deciding factor of which contractor stays in business in the future. Those who do not get educated and are unable to introduce, install and support advanced technology will be left in the dust, because customers are becoming more informed and are asking for technical solutions.

According to Miller, the guesswork of watering will soon to become obsolete.

September 2003