Irrigation Tech: Maintaining rain/freeze sensors

March 12, 2021 -  By
Rain/freeze sensor (Photo: Earthworks)

Rain/freeze sensors help ensure irrigation doesn’t run if it’s raining or if temperatures are below 35 degrees F. (Photo: Earthworks)

When irrigation pros run into inclement weather, rain/freeze sensors are a useful item to have on their clients’ properties. A rain/freeze sensor is a single device that detects rain and freezing temps. They’re designed to break contact with the common wire in the irrigation system if it receives a preset amount of rain or if the temperature drops below a certain point, typically 35 degrees F.

Chris Lee, president of Earthworks, a $26 million company in Lillian, Texas, says, “Having an evapotranspiration-based irrigation system for irrigation control is the Cadillac option since that takes into account the weather and recalculates your water schedule daily. If you can’t do that, you should install a rain/freeze sensor so that the system doesn’t run when it absolutely shouldn’t.”

Earthworks provides 50 percent maintenance, 30 percent design/build, 15 percent irrigation and 5 percent tree care services to mostly commercial clients.

Rain/freeze sensors have been mandated in Texas since 2008. Earthworks charges about $200 installed for a sensor and uses Weathermatic rain/freeze sensors that are connected to SmartLink controllers.

Lee explains why rain/freeze sensors can be useful for irrigation companies and offers tips for proper use and maintenance.

Set for success

Lee explains that it’s important to consider where the sensor is going to be located and to be sure to install the sensor where it’s open to the environment and free of obstructions like tree branches.

“If you have a rain sensor, don’t install it under the eave of the building or in a heavily treed area because it doesn’t get rained on,” Lee says. “And, don’t install a rain/freeze sensor next to a dryer vent because the heat emitted from the dryer will cause the sensor to think it’s warmer than 35 degrees outside.”


Lee says that because almost all sensors are wireless, it’s crucial to make sure you’ve got good signal strength. He notes that rain/freeze sensors typically last three to four years on commercial sites and longer on residential sites.

On the controller, techs should ensure the sensor switch isn’t set to bypass, which stops the sensor from working.

Companies also should remind clients to check and replace batteries each year. Earthworks sends notices Oct. 1 every year asking clients to replace the batteries and to call Earthworks if they’d like their sensors inspected.


It’s important to keep tabs on installed sensors. “In commercial settings, what you’ll see is they’ll call on a construction company to replace some siding and wherever the sensor was screwed into the building, the sensor got thrown in the dumpster and nobody says anything,” Lee says.

Cleaning sensors once a year is sufficient, he says. Earthworks technicians use a can of compressed air to blow out the cracks and crevices in the device and ensure there’s nothing sitting on top of it or growing around it.

Conservation versus safety

Rain/freeze sensors, wind sensors and flow sensors are the common types of irrigation sensors. “All of these are conservation devices, not safety devices,” Lee says, noting that if the rain/freeze sensor fails, an irrigation system could continue to run and create slippery and unsafe conditions in cold temperatures. Even if a rain/freeze sensor shuts off an irrigation system, a technician should still shut off the double-check valves to fully stop water from flowing.

“You can’t be lazy. You have to go shut your systems off,” Lee says. “They are designed to keep your system from coming on when its zero degrees — you just can’t rely on it from a life/safety perspective. Too often, we’ve seen people rely on that. It’s a $60 plastic part with a battery and an electronic transmitter that’s outside when it’s 120 degrees and outside when it’s zero. You can’t count on that to save people’s lives.”

This article is tagged with and posted in From the Magazine, Irrigation+Water Management, March 2021
Abby Hart

About the Author:

Abby Hart is the former senior editor of Landscape Management. A native Clevelander, she spent 10 years in Chicago, where she was operations manager of a global hospitality consultancy. She also worked as managing editor of Illumine, a health and wellness magazine; and a marketing specialist for B2B publications. Abby has a degree in journalism from Boston University’s College of Communication.

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