Field notes
When should rain and freeze sensors be replaced?
Test them every season and plan on new sensor discs and batteries about every two years. Replace the sensor any time the system runs in the rain or below freezing.
A rain sensor shuts the system off when it rains, and a freeze sensor keeps it off when the temperature drops near freezing. Texas rules require a rain or moisture shut-off device on irrigation systems, and many cities in our area expect both. A sensor that has quit working looks fine from the street, so most people only find out when the sprinklers run in a downpour or ice up the sidewalk.
What wears out:
- Rain sensor discs. Most rain sensors use discs that swell when wet and shrink as they dry. Over time they stop swelling the way they should. Plan on new discs about every two years.
- Wireless batteries. Wireless sensors run on a small battery in the sensor. Replace it about every two years, or sooner if the controller shows a lost signal.
- The whole sensor. Replace it when it fails a test, when the housing is cracked or sun-damaged, or after a mower or ladder knocks it loose.
How to test it: with a zone running, press the test button or wet the discs by hand. The system should shut off within a minute or two. We test the rain and freeze sensors on every care plan visit and tell you right away when one needs replacing.