If you have an automatic irrigation system you should have an automatic rain shutoff device, or rain sensor, installed. This device detects rain and prevents your sprinklers from running while it is raining. All irrigation systems are required to have this, but if you have an older system it may not have been installed. Even if your system had one installed years ago, it's always a good idea to make sure that it is working properly. Now that we are in the rainy season, it's very important to make sure you have a working rain shutoff device. Rain shutoff devices work by interrupting the irrigation system once a certain amount of rain has been detected.
Your rain shutoff device can be tested during normal rainfall events by setting out several containers such as tuna or cat food cans. At least three containers should be placed in the yard so that rainfall can accumulate in these containers. Measure the depth of water in each container with a ruler, and when the containers average about a half inch of rainfall, set the rainfall sensor to a half inch and manually turn on the irrigation system at the controller. If it's working properly the irrigation system should not run. If the system does run, the rainfall sensor may need to be cleaned, relocated so rainfall will contact it, or repaired or replaced. Sensors with electrodes may require cleaning of the electrodes and/or cleaning of the catch container. Sensors with a weighing dish or cup may require periodic cleaning of the container. Refer to the manufacturer instructions or contact your irrigation maintenance professional.
For more information on rain shutoff devices and their proper maintenance, visit "Residential Irrigation System Rainfall Shutoff Devices" at edis.ifas.ufl.edu /ae221.
For those without an automatic irrigation system, you can rely on a good old-fashioned rain gauge to tell you when you've gotten enough water. Place the rain gauge in an open area away from trees and buildings and be sure to empty it after each rain event to ensure an accurate reading. For more info on rain gauges and even how to make one yourself visit gardeningsolutions. ifas.ufl.edu/giam/maintenance_and_care/watering_and_irrigation/rain_gauges.html.