Rain Shutoff Devices for Automatic Lawn Sprinkler Systems
Automatic sprinkler system controllers are programmed to turn on and off on a specific day and time. The controller doesn’t know if it’s sunny and dry outside or it’s raining. For this reason, all lawn sprinkler systems must have a rain sensor.
The sensor determines whether or not it has rained enough to skip a watering cycle. There are three basic types of rain sensors. They all serve the same purpose: to prevent your system from over-watering your lawn or garden. How do you do that? The electrical connection between the sensor and the controller of your sprinkler system is interrupted when a certain amount of rain activates the device. The sensor breaks the electrical connection so electricity cannot flow to either the sprinkler valves or pump start (if your system is in a well without a pressure tank).
One guy breaks the connection by weighing the water in a rain collecting cup. The problem with this type is that the occasional leaves, sticks, or lizards will find their way into the collection cup and thus shut down the system.
The next type uses electrodes to determine how much water is in the collection cup. This type of rain sensing device also has a system problem to collect things other than rain in the collection cup.
The most common type of rain sensor used by professionals is the expansion disk device. This type of sensor does not use a collecting container; Instead, the rain causes the cork discs to expand. This device uses a pressure switch to break the electrical connection. These can be adjusted in ¼ “increments to the desired rain fall setting. This setting is generally set to turn the sprinklers off after ½” of rain has fallen.
The most important aspect of installing a rain sensor is where to place it. It should be installed in an area that is not obstructed by trees, overhanging ceilings, or anything else that may prevent rain from reaching the sensor. If it is a wired sensor, the location is usually near the sprinkler controller. The wires must be connected inside the controller valve wiring panel. This allows for easier electrical troubleshooting of the system as the sensor can be easily disconnected.
In recent years, FM wireless rain sensors have become very popular. Although they are more expensive than wired devices, the ease of installation and increased placement options outweigh the cost. Most wireless units come with bypass switches built into the device. Some digital controllers also offer bypass options for both wired devices and wireless rain sensors.
No matter what type of rain sensor you choose, all rain sensors offer many advantages over not adding this detector to your automatic sprinkler system. Some of the immediate and long-term benefits include:
o Save money. Whether you pay for city water or spend electricity running a pump, the money you save over time will be more than paying for the rain sensor.
o Extends the life of the sprinkler system. Irrigation systems are made up of moving parts. If system parts are used less frequently (during the rainy season), they last longer.
o Protects water resources. By limiting overuse of your sprinkler system, rain sensors reduce excess runoff that carries fertilizers and pest control chemicals into our shared water supply.
o Canned water. Less water is wasted when less supplemental water is needed for your lawn and garden.
How much money can you save with a rain sensing device?
It will vary based on your water source (city, claim, or well) and where you live (water costs, electric rate, weather). Here is an example that demonstrates the benefits listed above:
Seminole County, Florida.
Description of the system:
o Designed to water a quarter acre of lawn and programmed to apply ½ “of water each time the system operates.
o This program would equal 6,788 gallons per irrigation cycle.
o This system (on city water) pays $ 2.30 per thousand gallons.
o Each time the rain sensor interrupts a sprinkler cycle, it would save $ 15.61
According to a recent study in Florida, the use of a rain sensing device averaged 45% water savings for single-family residential water use.
The next time you see a sprinkler system running in the rain, you know it doesn’t have to. Rain sensors are affordable solutions to conserve our water, protect our water resources, and save you money.