Author Archives: Scott Duncan

Is A Local Rain Sensor Important?

In many places in the continental United States, a significant amount of natural rainfall occurs during the growing season. All of this rain is not available for plant use. A large percentage will be lost to evaporation, runoff, or deep percolation. What reaches the roots and is utilized by the plant is called effective rainfall. For example, this year in central Virginia (using a very conservative formula) we still end up with 12.26 inches of effective rainfall for the April to October growing season with an evapotranspiration (ET) plant water requirement of 34.25 inches for the same period. This means that natural rainfall provided almost 36% of the water required for the 2013 growing season. This example emphatically demonstrates the importance of a well functioning local rain sensor.

Much of the rain that occurs during the growing season is localized. We all know that it can rain 1.5 inches on one side of town and ¼ inch on the other. The only way to account for these large variations is to install a local rain sensor with your specific system. When functioning properly, this sensor will react to the rainfall that occurs at your specific location. It will interrupt any scheduled irrigation cycle and not allow it to operate until the rain sensor has dried out, roughly paralleling soil conditions.

If you have a sensor it must be installed at a location that is open to natural rainfall. It can’t be installed under the canopy of a tree or close to the controller just because this is convenient for the installer. It must be located where it will receive natural rainfall so that it can react to actual weather conditions. Most of these units, especially the wireless devices, rely on a small battery in the transmitting unit. These batteries usually need to be replaced annually. If this battery is dead or weak, the rain sensor will not operate properly or at all.

In summary, the local rain sensor is a critical component of your landscape sprinkler system. A fully functioning and well-maintained device will prevent the operation of your system when not needed and save you large amounts of water and dollars. As per the example in the first paragraph, this small device could have saved the customer over 1/3 of the cost of operation of their landscape sprinkler system in 2013. Many of the units available on the market today have the ability to be programmed to interrupt irrigation for extended time periods even after the hydroscopic disks have dried out and the rains sensor contacts have closed. Take advantage of this low hanging fruit today. Make sure that you have a local rain sensor properly installed and fully functioning.


Why should you be interested in a smart irrigation controller?

Well, did you know that on average, more than 50% of the water used by households is for the maintenance of landscapes and lawns? You can reduce your outdoor water use, maintain a healthy and attractive landscape – and save money every month on your water bill by converting from a conventional to a “smart” irrigation controller.

Smart vs. conventional irrigation controllers

Let’s first define what makes a controller “smart” and how it differs from a conventional controller. A conventional controller is really just a timer that turns water on and off according to a pre-programmed schedule, regardless of the weather conditions. According to landscape professionals, over watering is the most common problem in home landscapes. As much as 70 to 80% of all plant problems are related to incorrect watering. If you want to change the operating schedule of the controller, you have to enter new program information. Many times the original schedule that is entered into the controller when the system is started up in the spring is never changed. This “set it and forget it” approach is inherently inefficient. A conventional controller will only operate the last schedule that it received. It will not adjust as the weather changes.

A smart irrigation controller will monitor and use information about environmental conditions for a specific location and landscape, information such as soil moisture, rain, wind, evaporation rates, plant transpiration rates and more, to determine when to water and when not to. A “smart” controller will track along with the changes in the weather as well as the specific requirements of your landscape. It will maximize water use efficiency, often producing water savings of 30% or more. In addition to the money and water saved, your lawn and landscape will thank you. According to landscape professionals, over watering is the most common problem in home landscapes. As much as 70 to 80% of all plant problems are related to incorrect watering.

Which smart irrigation controller is right for you?

How do you know what smart irrigation controller product to select? There are several important steps to take when deciding which smart controller is right for you. First, conduct a sprinkler system inspection. A smart irrigation controller will work properly only when the entire sprinkler system is operating optimally. It is essential to conduct a full sprinkler system inspection, or audit, prior to installing a new smart controller. This audit will identify any and all issues such as leaks, malfunctioning hardware, water pressure, site coverage, and uniformity that are impacting the effectiveness of your entire system. When you correct these problems, your smart controller will be able to deliver the specific amount of water required by your landscape.

Next, select an irrigation professional (preferably a Certified Landscape Irrigation Auditor – C.L.I.A.) who is capable of recommending the smart controller product that works best for your particular situation, and understands how to gather and input all of the information that will allow the controller to make accurate adjustments. Proper installation and programming with complete and accurate information is critical to the performance of any smart controller product.

Monitoring and adjusting the irrigation controller

Finally, after the controller is installed and operational for a short period, usually between two and six weeks, at least one monitoring visit should be carried out in order to make further adjustments to the program as needed. The purpose of the visit(s) should be to adjust the run times of each station to a point where the stress threshold of that particular zone can be determined. Every landscape is unique, and will require this type of fine tuning.

Once the proper amount of water is determined for your particular landscape and weather conditions, it is important to deliver this water in a way that insures it all gets to the root zone. With our clay soils, multiple irrigation cycles are usually required to prevent runoff. Make sure your smart irrigation controller is taking all of the system and environmental information (i.e. precipitation rate, distribution uniformity, landscape coefficient, soil type, & root zone depth) into account or have your irrigation professional write an auditor base schedule which determines the number of irrigation days per period, total run time per day, run time per cycle, and cycles per day.

In summary, you should be interested in a smart irrigation controller because it represents a significant improvement over conventional controller technology. When installed and programmed properly, these controllers can produce substantial water savings. Utilize an irrigation professional who is well versed in this technology to insure that you select the best product for your needs and maximize the benefits you receive from this selection. While smart  controllers are not a panacea for the inherent inefficiencies found in many landscape irrigation systems today, they can play a major role in the on-going effort to utilize water more efficiently. Let’s all work together to help conserve our most precious natural resource!