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We've all seen it. Rain is falling – maybe it’s pouring, or even just sprinkling. Driving down the road, you pass a person’s home where the irrigation system is running like it’s the driest day in July. It’s watering the sopping wet grass and streams begin forming, water bleeding on to the sidewalks, driveway and street.

What a waste, you think. The only thing that system needs is a rain sensor, and the system wouldn’t be spraying H2O all over a soaking lawn.

“The rain sensor is the most important part of an irrigation system,” says Yoni Wiss, a project manager at Hydro-Tech Irrigation in Haymarket, Virginia. “And, even more valuable is a controller connected to a weather station that is very local, so you know a week in advance the weather that’s coming to your yard.”

Hydro-Tech uses WiFi controllers that claim to save its owners up to 50 percent on their water bills. “If the temperature is too cold or if rain is coming to the area, the controller tells the system to turn off,” Wiss says.

Customers love the savings. And, that’s how Kip Summers, owner of Summers Irrigation in Waterford, Michigan, sells rain sensors to customers getting a new irrigation system, or clients who are thinking about adding a sensor to a system they already have. “When I am talking to a homeowner, the way I break it to them is by asking, ‘Do you like to save money?’” Summers says. “They’ll respond, ‘Everyone likes to save money.’ And I tell them the initial cost and that it will probably take about a year to get your money back. Then, I explain how rain sensors work.”

That return on investment is an estimate because some years there is more rain and you’ll save more money by having a rain sensor, so the irrigation system doesn’t run as precipitation is falling from the sky. Other years, it might take a bit longer to “make up” the cost of the sensor, particularly if it’s a dry summer. “But a year is the rule of thumb,” Summers says.

Upfitting an irrigation system to include a rain sensor – and perhaps a weather station, too – just makes good sense.

Selling Water-Saving Benefits.

First, letting property owners know just how easy it is to add sensors to an existing system can help them understand that achieving water savings is within reach. Summers explains how the wireless sensors work. Because they are WiFi enabled, “you can pretty much hook them up to any controller,” including 10-year-old irrigation systems. No wire-running or digging is required.

Rain sensors tell the system to turn off when it’s actually raining because the sensor detects precipitation. Rain sensor gauges are mounted and connected to the system (again, wirelessly). The gauge absorbs water and expands as more rain falls. This signals to the irrigation system: don’t run now.

A weather station connected to an irrigation controller streams local weather forecasts and sends messages to the controller to not run when rain is expected. So, while the rain sensor only turns off the system while rain is falling, a weather station is a predictive tool. It can instruct an irrigation system to turn off if rain is forecasted that day.

“Say your grass needs 1 inch of water, and you’re going to get an inch of rain tomorrow,” Wiss says. “The system will send you a text message saying that it will not run the next two days because weather stations No. 1, 2 and 3 say you are going to get an inch of rain.”

A weather station combined with a rain sensor leads to more water savings, Wiss says. Say it rains overnight. An irrigation system is programmed to run at 6 a.m., but the yard is thoroughly soaked. Because rain isn’t falling, the system will run anyway if only a rain sensor is in place. But with a weather station, the system will know that it rained and the yard only needs a certain amount of water, so it will save water by not turning on.

Weather station controllers aren’t brand-new, but the technology is evolving, and Summers says he always recommends a rain sensor to clients but does not generally install the weather stations.

However, he adds, “This is the up-and-coming thing.”

There are also moisture sensors that detect how much water is in the soil. This way, the sensor will disrupt the irrigation system if it rained all night, so it won’t turn on at 6 a.m.

Wiss says moisture sensors can be used on larger properties, or those that have various grades or different levels of sun exposure.