Rain Sensor for Irrigation: When and Why Should You Use One?

Efficient water management is crucial in professional irrigation systems: a rain sensor stops or prevents irrigation cycles from starting during rainfall, avoiding water waste and crop damage.
In this article, we explain how a rain sensor works and the benefits it brings to irrigation systems, ensuring simple and precise operation.

What Is a Rain Sensor for Irrigation and How Does It Work?

A rain sensor for irrigation acts like a switch that uses a hygroscopic disc as its detection principle. This disc swells as it absorbs rainwater.

By connecting the rain sensor to the dedicated input on the irrigation controller, irrigation is interrupted during or after a rain event. When the disc is wet, it sends a stop signal to the controller, and irrigation only resumes once the disc has completely dried.

Sometimes professionals contact us reporting systems that fail to restart irrigation even hours after the rain has stopped. This happens because the hygroscopic disc remains damp and continues to inhibit the start. To reduce drying time, we recommend installing the rain sensor in a well-ventilated area and adjusting the humidity threshold.

It’s also important to remember where to install—and where not to install—a rain sensor: if placed too close to a sprinkler, it may be hit by the spray and interrupt the irrigation cycle, mistaking splashes for rain. At the same time, it must be exposed to actual rainfall, so do not place it under canopies, covered terraces, or inside garages.

The Benefits of a Rain Sensor in an Irrigation System

• Water savings and lower costs: By stopping irrigation during and after rain, you avoid waterlogging and reduce consumption by up to 20%.
• Fewer manual interventions: No need to constantly monitor local weather, as the sensor automatically manages start and stop.
• Plant protection: Excess water can promote fungal diseases. With a rain sensor, plants always receive the optimal amount of water, avoiding water stress or over-irrigation.

When to Install a Rain Sensor in an Irrigation System

Installing a rain sensor at the start of the irrigation season is especially beneficial in areas with intermittent rainfall, as it maximises water savings from the very first cycles. Even in drier climates, while less urgent, the sensor remains a key ally for automatic control of watering.

In micro-irrigation systems, the sensor can optimise consumption and ensure more uniform soil moisture.

Connected to a smart controller, a standard rain sensor stops irrigation during or after a rain event. Our Acqua Vision rain sensor, however, not only performs this function but can also communicate with other Vision system devices via Bluetooth 5.0 or, when paired with a Nuvola device, via Wi-Fi, enabling full management through the Rain Vision App.

Our range of rain sensors includes three other solutions:Acqua Click Metal, with a robust metal bracket for extreme conditions; Acqua Click Plastic, with a lightweight, versatile plastic bracket; Acqua Click Jack, featuring a standard jack input for quick and flexible wiring.

How to Maintain Rain Sensors in an Irrigation System

To keep your rain sensor reliable, clean the hygroscopic disc regularly with demineralised water, removing any deposits that could affect its sensitivity. After cleaning, always check that the sensor correctly sends the stop signal to the controller.

Once a month, simulate a rain event by spraying water on the hygroscopic disc and verify that the irrigation cycle stops. This simple test ensures the sensor is working properly.

Start saving water with precision and reliability: buy a rain sensor for your professional irrigation systems today!