How Does a Rain Sensor Work?

A rain sensor works by detecting rainfall and shutting off an irrigation or sprinkler system when no additional watering is needed. The sensor is connected to the wiring of the irrigation system. When rain is detected, the circuit to the system is disrupted, interfering with the electrical flow from the controller of the irrigation system that activates the valve.

Rain sensors can save money on utilities as well as conserve water and prevent the over watering of green space. Many areas have legislation that requires these devices to be present in sprinkler systems, and some utility companies offer rebates to the purchaser of such devices. Rain sensors are installed close to the controller.

Suggested areas where rain sensors can be installed include building roofs, light posts and on or near satellite dishes, fence tops or any open area. It is recommended that rain sensors be tested several times a year. To do this, place three to five small containers in the yard on a rainy day. Allow one half inch of rain to accumulate in the containers. Set the rain sensor for one half inch. Attempt to turn on the irrigation system manually. If the rain sensor is working properly, the irrigation system should not come on. If the irrigation system is activated, the problem may be due to loose wiring or the need for cleaning and repositioning. In some cases, a replacement sensor may be needed.