Irrigating in the Rain?


GREEN COVE SPRINGS – Driving around the county in some of the recent weather, it is not that uncommon to see the occasional irrigation system still watering away as the rain pours down. This is probably a sign of a broken or, even worse, non-existent rainfall shutoff device.

Florida is one of the few states that requires a rainfall shut-off device on all automatic irrigation system and these tools have some great advantages such as conserving and protecting water resources, saving money, and reducing diseases that thrive in overwatered situations. If you do not have a shut-off device or yours is not functioning, they are readily available wherever irrigation supplies are sold and can be installed by you or an irrigation professional.

Rain Shut-off Devices

Depending on the site, these devices can vary highly from location to location but they usually work by sensing the amount of rainfall that accumulates during an event. Some types include those that capture and function on the weight of the water in the sensor, those that use electrodes to check for a circuit when rain accumulates and those that utilize material that expands when it rains, triggering a switch.

No matter the type of rain shut-off device installed, it must be functioning properly. Check sensors for damage and refer to the manufacturer’s instructions on how to set the device. Another requirement for most sensors is that they are able to capture unobstructed rainfall. Make sure the sensor is not being blocked by vegetation or structures and is not capturing water running off from rooftops. It may take some experimentation to find the best possible location and settings to make sure the sensor is allowing watering to occur when not needed but also not interrupting needed events.

Soil Moisture Sensors and Smart Controllers

With newer irrigation controllers, there are more options to help keep your system more automated and fit our climate. One of the most common of these technologies is soil moisture sensors, which also qualify as a rain shutoff device, replacing the rain sensor. These devices are connected to your controller but are installed in the soil, measuring the amount of water available to plants and will stop the irrigation from running when sufficient water is present or will adjust the timing of irrigation to be shorter or longer depending on need. Most irrigation systems can be retro-fitted with this device and it can help further your water savings.

Another technology that works alongside these devices is a “Smart” Irrigation controller. They communicate with all of your zones and the sensors to ensure watering is done properly. Some newer timers also work through the internet to receive weather information to adjust irrigation events to match the expected needs of the landscape and also coordinate with cell phones, allowing you to make adjustments while away from the device.

Remember that no matter what type of devices or controllers you have, you are limited to your two days a week of watering by the St. Johns River Water Management District and you are not to water between 10 a.m. and 4 p.m. If your irrigation devices and controllers are working properly, and with proper setting and calibration, some of our precious water resources can be saved for other uses.

If you have any questions contact the University of Florida/IFAS Extension Office at (904) 284-6355. Visit to see and register for upcoming classes or call the office for more information.


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