Have you checked your rain sensor lately? Does your automatic lawn sprinkler system even have a rain sensor? Since 1991 there has been a mandatory law here in Florida that states that all automatic lawn sprinkler systems installed after that date must have a rain sensor device installed. This law has been loosely enforced, but more counties in Florida are finally starting to get more serious about this.
If you don’t already know, a rain sensor is a small piece of equipment that hooks up to your automatic lawn sprinkler system and shuts the system down if there is adequate rainfall. Most brands of rain sensors can be adjusted to shut the system off from 1/8″ to 3/4″ of rain. You may want to adjust it according to the type of lawn and landscape that you have and other factors such as soil type of sun/shade conditions.
The way most rain sensors work is by utilizing a small disc made from a cardboard like material that swells out when it becomes saturated. When the disc swells out, it puts a break in the common or negative wire(s) in the system which in turn doesn’t allow the pump to turn on and cuts the electricity to the electric valves so they do not open. The power to the timer still exists so that the date, time, and cycle program information are not interrupted.
Even though there has been a law in effect that requires rain sensors, many systems still don’t have them. The law has not been heavily enforced, and there are certain areas that don’t require inspections and therefore the contractor or homeowner can get by without installing one. Even if your area doesn’t require an inspection for your system, I would still highly recommend installing one.
Although beneficial to saving water and not over-water the lawn, some contractors feel that rain sensors are a hassle. I agree that they can be, especially when the homeowner or customer doesn’t know that their sensor is set for a specific amount of rainfall. You may get a call from someone who says “it’s raining, but my system is still running”, but the sensor may have not yet measured enough rain to shut the system off.
You also get calls when people don’t see there system run a day or two after it rains. This is because it could take a couple of days for the disc to dry out let the system go back to normal operation. The illumination sensor is designed to dry out at approximately the same rate as the soil. New timers have a light and/or display that says “sensor” or something similar so that the user knows that the rain sensor is active and will prevent system operation. Most modern timers also have a manual over-ride so that if you need to check the system out while the sensor is active, you can temporarily disable the sensor and turn on the system.