A properly working rain sensor prevents inefficient watering when it is raining.

How to Test a Rain Sensor for a Sprinkler System

by Mary Lougee

A rain sensor communicates with an irrigation system controller through a wired or wireless connection to prevent irrigation cycles from occurring when there is rainfall. The two main types are cork-disk and catch basin types. Cork-disk types expand with moisture to turn off the watering cycles, and catch basins operate by the water weight or electrode position to delay an irrigation cycle. Testing your rain sensor for proper operation is an integral part of your irrigation system to conserve water and your costs.

1. Cork-Disk Rain Sensors

1 Turn on the watering zone closest to your rain sensor on your irrigation controller. You may wait until it is close to the time schedule for an irrigation cycle or turn it on manually at any time.

2. Cork-Disk Rain Sensors

2 Observe your sprinkler heads in the zone you turned on. They should start emitting water onto the lawn

3. Cork-Disk Rain Sensors

3 Press and hold the button on the top of your rain sensor. The water should stop flowing from the sprinkler heads.

4. Cork-Disk Rain Sensors

4 Release the button on top of the sensor. The sprinkler heads should start irrigation on your lawn.

5. Catch Basin Rain Sensor

1 Place three empty, shallow cans on your lawn when you expect it to rain. These serve as alternate catch basins for measuring rainfall.

6. Catch Basin Rain Sensor

2 Set your catch basin rain sensor to 1/4 inch. Depending on the model, there is a plastic piece calibrated in inches that turns or slides up and down to set it.

7. Catch Basin Rain Sensor

3 Allow the cans to collect rain. Pour all three cans together and divide by three to get the average of rainfall in your lawn.

8. Catch Basin Rain Sensor

4 Turn on your irrigation controller manually when the average rainfall from the cans is 1/4 inch or more. The sprinkler heads should not initiate irrigation.

Items you will need

  • Irrigation controller
  • 3 empty, shallow cans, such as from tuna or catfood
  • Measuring tape

Tips

  • If a rain sensor operates your irrigation system when it shouldn't, it may require cleaning of the catch basin or electrodes on wired models.
  • Batteries that are operating at a low rate may need changing on a wireless model of rain sensor for correct operation.
  • Check and clean electrodes on wired models between the rain sensor and the irrigation controller if your model does not operate properly. Corrosion interferes with the flow of electricity and can prevent operation.

Warning

  • Avoid placing a rain sensor under the eaves of a structure or under tree branches. Excess water runs off eaves and branches block the rainfall to make the sensor unreliable.

Photo Credits

  • Comstock Images/Comstock/Getty Images