Sept. 23 2010 12:00 AM
How many times have you driven down the street or on the Interstate in the pouring rain and noticed that sprinklers are putting down even more water? While Mother Nature is doing her work by quenching the thirsty soil, the automatic sprinklers are running . . . and wasting water.

When programmable sprinklers gained popularity in the mid-1960s, we had the ultimate answer to keeping the landscape green. However, there was one missing piece to the puzzle: when it was raining, the only way to shut off the sprinklers was to go to the control box or central controller and manually shut them off.

But today, with the next generation of moisturesensing devices, problems like the one cited above no longer need to exist. Wasting water is never a good thing, especially these days; coupled with the water shortages and stringent water controls, rain- and moisture-sensors have become even more important tools in your toolbox.

These smart water devices have gained so much popularity with water purveyors—as well as the municipalities and cities in many states—that sensing devices are now written into their code. In many cities, it is now mandatory to have such a device hooked up to the controller in your home.

Sensors have been around for the past 30 years. One of the simplest devices, and one that’s easy to install, is the rain sensor. Rain sensors measure the amount of rain that has fallen onto the surface of the site. The original approach used a hydroscopic disc made up of a material similar to cork. As this disc comes into contact with rainwater, it absorbs water and expands like a sponge. If enough water is absorbed, the disc willexpand to the point where it triggers a switch that turns off the irrigation system. When the disc dries, it will shrink and release the switch, turning the system back on. This process is still in use today.

“We include a rain-sensing device on every installation,” says Robert Diersing, owner, RI Lawn Sprinkler Systems, Akron, Cleveland and Columbus, Ohio. “Although it’s not a requirement according to the municipal code, we feel it is the right thing to do.”

Another rain-sensing device for measuring water, called the ‘tipping bucket,’ was introduced only in the last couple of years. This rain sensor basically acts as a catch-can, by collecting rainwater as it falls and storing it in a tiny catch basin. Once the water reaches a pre-determined level, the weight of the water will tip the bucket and send a signal to the controller to turn off the system.

These rain-sensing units are usually mounted on the roof of a home and should not be obstructed by trees or debris. They are easy to install; simply connect the wires from the sensing device to the controller.

Another way to measure water content is with a soil moisture-sensing device. Again, these devices have been around for many years and originally had a reputation of limited acceptance. Some of the first models of soil moisture-sensors were developed with materials of the time that didn’t hold up. Early sensors often deteriorated shortly after they were installed in the ground, as the acidic properties of the soil would cause the metal to degrade.

They were also vulnerable to electrical surges and lightning strikes, which could make the devices malfunction. Early sensors also ran the risk of altering the properties of the soil because of the electrical activity, which could make it more difficult for them to give accurate soil moisture measurements.

An add-on device can be retrofitted to an existing controller.

Modern devices are now made from noncorrosive materials such as ABS plastic, stainless steel or PVC-jacketed wiring. Electrical components in some moisture sensors are encased in a granular matrix made of gypsum and chalk, to provide an extra layer of protection. These units are excellent for controlling the amount of water used on a site.

There are a number of different brands and types of soil sensors, but the basic technology is the same: they give the controller accurate estimates of how much water has been absorbed by the soil.

These sensors are installed based on different hydro-zones, which are areas in the landscape that are grouped by water demand. Plant material that’s in a very high moisture threshold, like clay, should be grouped together. By the same token, drought-tolerant plants should be kept together. Each hydro-zone needs its own sensor, so that you can really custom-fit the needs of each particular plant grouping.

Once they are placed in the ground, the sensors are wired back to the controller. Now the system can make watering “decisions,” based on the moisture content. The valve that has the moisture sensor wired to it makes a choice, based on the actual soil moisture reading in the ground, and sends a signal to the controller.

If there is enough moisture, the signal to the controller or valve is to bypass this station. So basically, the way it works is that the sensor measures the available water in the pore space of the soil and makes a decision before each cycle starts whether or not to apply water.

Don’t be afraid of change

It’s not uncommon to find con tractors who fear technology. They don’t realize that today’s soil moisture sensors lead the vanguard of smart water technology. “It’s important to try out newer moisture sensors before passing judgment on the technology as a whole,” said Christine Hawkins, water management specialist at Ewing Irrigation. “If you just overcome your aversion to the technology and give them a try, you will probably end up liking how easy they are to use.”

“The secret to success is picking the right product,” said Rick Foster, senior product manager at Rain Bird. “It’s important that a sensor is reliable and accurate.”

If the newer systems are too daunting to learn, add-on devices are also an option.

“The advantage of an add-on device is that it can be retrofitted to the current controller onsite,” said Tom Penning, president of Irrometer in Riverside, California.

“If you have a controller that the contractor is familiar with, rather than having to teach him about a new one, or learn about one that is much more sophisticated, he can just add the device on to an existing clock to make it more efficient, or make it a smarter clock,” he added.

The conventional time-based controller is connected to the addon device, which just functions as a switch. Then, just like other moisture sensor products, if your controller is programmed to water Wednesday morning at 8 a.m. and the sensor says that the soil is still moist, the scheduled watering is overridden.

Another option is to take the sensor, which is feeding directly into the controller, and have the sensor signal the controller to initiate irrigation whenever it happens to be dry, rather than waiting for a scheduled watering. “There are a couple of different ways it can be done, but the base technology is the same,” Penning said.

An easy sell

Awareness of water sustainability is gaining traction as more mandatory watering restrictions are put in place. Many cities and municipalities now require that their residents install rain-sensing devices on their homes.

From a contractor’s point of view, this is a huge opportunity: we need to recognize this as a win-win situation. Just imagine going to all the clients in your database and proposing that they allow you to retrofit their irrigation system with a smart controller and rain- and moisture-sensing devices. Your customers will be ecologically compliant, they’ll save money on their water bill, and with the rebates they can receive—it won’t cost them anything for the retrofit!

Cutaway illustration of an installation of a moisturesensing device.

Equally as important, it will generate much needed revenue for your company, especially in these tight economic times. Everybody wins.

There are many water purveyors, or municipal suppliers throughout the country who currently provide product rebates or grant programs to their customers if they purchase and install moisture sensors.

Some programs offer higher rebates than others.

For example, if you live in Seattle, Washington, and you install a controller that has evapotranspiration (ET) capabilities and also install a rain or moisture sensor, your customer can be eligible for a rebate that can add up to as much as $375.

Similar programs can be found in Collin County, Texas; Tampa, Florida; Pasco County, Florida; Reading, Massachusetts; Louisville, Colorado; Denver Colorado, as well as New Mexico, throughout central Utah and throughout California.

Many of the cities and water authorities realize that by replacing conventional controllers with smart controllers and installing rain- and moisture-sensing units, the homeowner will use less water and can conservatively save between 30 to 40 percent on their water bill.

Although these rebates go to the homeowner and do not provide incentives to landscape contractors, what a great selling tool it becomes. Stay aggressive in your marketing and you’ll make many of your customers happy while you reap the ben- Photo courtesy: Rain Bird efits of added business.

Many contractors are creatures of habit and are reluctant to make changes. However, times are changing and we have to change with them if we are to go into the next decade. “We have systems that are bullet-proof. They’re easy to install and they work exceedingly well,” says John Fordenwalt, president of Baseline Systems, Boise, Idaho. “If you’re trying to grow your business, especially in a down market, this is the way to do it. It’s the most important thing going on in irrigation right now.”

Now is the time to differentiate yourself and help your company expand. You’ll also sleep a little better at night, knowing that you’re doing your part for the green movement to conserve resources.

As with other aspects of landscape contracting, there is a learning curve. The sooner you get on the path, the further ahead you’ll be against your competition. As you embrace the new technology, you’ll have the opportunity to get on a faster track for growth. In the long run, you’ll be the leaders of the next boom.

Although these devices may vary in size, shape and form, they are effective tools.