Rain shut-off devices
Rain Shut-off Devices
Residents with an automatic irrigation system in the state of Florida are required by law to have a fully operational rain shut-off device. These devices are crucial in preventing overwatering, which can lead to plant disease, polluted runoff into freshwater systems, and high water bills.
They work by monitoring rainfall in one of several ways, like measuring the electroconductivity (EC) of the water, water weight collected in a catch cup, or moisture absorbed by expanding cork discs. They might also receive weather data from a local station. After a certain level of moisture has been reached, the device sends a signal to the irrigation system controller to delay programming until conditions are dry again. Read on below to learn about what some of these devices look like, some of their benefits and disadvantages, and tips for installation.
Rain sensors are often considered the standard when it comes to rain shut-off devices. They are required if no other system is in place. They may not be the most sturdy of the bunch, but they are inexpensive, widely available, and relatively easy to install. When it comes to rain sensors, there are both wired and wireless versions. Wired sensors connect directly by wire to the irrigation system controller through the rain sensor port, often marked “SENS”. They can be connected to older models through the common wire as well. Wireless sensors have a receiver that connects to the controller in the same way, which allows for greater range when it comes to rain sensor placement.
The most common and effective rain sensors are cork-disc sensors, which override the system when sufficiently wet. It is important to choose a model with at least 2-day programming to avoid premature irrigation on weeks with significant rainfall. Sensors should be placed in an open area that gets full exposure to rainfall. A popular place to mount rain sensors is on the side of the roof near the irrigation system controller. See the video below to learn more about the different types of rain sensors and sensor installation.
Pros: Easy installation, affordable price
Cons: Must be wired to controller, needs an open area, needs regular replacement
Rain Sensor Maintenance
Cork disc rain sensors are one of the most common rain shut-off devices, but they need regular maintenance.
Follow the steps below to test your sensor.
- Turn on one of the irrigation zones by your rain sensor.
- Point a hose at your sensor and run water for 2 minutes.
- If your zone does not shut off, your sensor may need maintenance.
If you have a wireless sensor, make sure that the settings are correct on the box connected to your controller. Replace the batteries if needed. The cork may disintegrate over time, but you can buy replacement discs instead of a new unit.
If your sensor is still not working, it may need to be replaced. Read on to see some of the other devices you can use to replace your damaged unit.
If you prefer a more hands-off approach to irrigation programming, you may be interested in investing in a smartphone controller. Smartphone controllers are indoor devices that help you control your irrigation system from a smartphone application and use local weather data to determine when to water.
Though they may not be as accurate as devices that collect rainfall data on-site, they have the advantage of remote access. If you are someone who is away from home for extended periods of time, it can be helpful to access your system’s programs from your phone. Depending on the model, some smartphone controllers can also account for plant type, sun exposure, and other factors when determining when and how often to water.
Pros: Easy to program, can be controlled remotely through your phone
Cons: Must be mounted indoors, weather readings may be inaccurate
Soil Moisture Sensors
Soil moisture sensors (SMS) use metal probes to measure moisture within the root zone. Often, moisture is measured as electrical conductivity, or EC. Many models of SMS have a separate controller that attaches to your irrigation timer. The probes continuously provide data to the SMS controller, which will send a signal to your irrigation timer to shut off your system’s valves if the site conditions are “wet.” If the probes measure the site as “dry,” then that signal will no longer transmit, and your programming will operate as usual. As with other rain shut-off devices, this threshold can be adjusted to match the University of Florida’s recommendation of 1/2 to 3/4 inch water per irrigation application.
These sensors must be buried underground at least a few inches below your turfgrass. When it comes to installation, it is important to pick an area that is representative of your yard, as most residences only have one sensor installed. You can learn more about how soil moisture sensors operate in the video below.
Pros: Very precise readings, easy to “set and forget”
Cons: Requires connection to controller, probes need to be buried underground
For those without an automatic irrigation system, you can still actively participate in saving water by monitoring rainfall with a rain gauge. Most rain gauges are composed of a tube that collects rainwater from storms.
A standard rain gauge consists of a funnel emptying into a graduated cylinder. Users can keep track of rainfall by measuring the amount of water in the cylinder. These gauges come in a variety of models and types, and you can purchase them online or from most home improvement stores.
Remember to empty your gauge after each rain event to ensure an accurate reading. Some of the higher tech models automatically empty themselves, so it may be worth the investment if you would prefer a lower-maintenance device. Whichever make or model you choose, place your gauge in an area where it can get regular rain exposure.
Want a free rain gauge for your yard? Sign up to volunteer with the citizen science project CoCoRaHS and help contribute valuable precipitation data for your area. Bring your email confirmation to our office at Twin Lakes Park to receive a free rain gauge while supplies last.
No matter what device you choose for your system, it’s important that you keep it well-maintained. Check periodically to make sure that your system shuts off on weeks with at least 3/4 inch of rainfall. If there are any issues, be sure to promptly make any necessary repairs or replacements. It is also important to follow the watering restrictions for your area when programming your controller. Sarasota County residents can check here to see their allotted watering day(s).
For more information on irrigation and water conservation in general, visit our Water Resources website.
An Equal Opportunity Institution. UF/IFAS Extension, University of Florida, Institute of Food and Agricultural Sciences, Tom Obreza, interim dean for UF/IFAS Extension. Sarasota County prohibits discrimination in all services, programs or activities. View the complete policy at www.scgov.net/ADA.