Landscape and Irrigation is read by decision makers throughout the landscape and irrigation markets — including contractors, landscape architects, professional grounds managers, and irrigation and water mgmt companies and reaches the entire spetrum.
Issue link: http://read.dmtmag.com/i/506883
14 May/June 2015 Landscape and Irrigation www.landscapeirrigation.com STAYING CURRENT "Mistakenly oversimplified" best describes the common percep- tion of irrigation system design, installation and maintenance. Not only are the consequences of this misperception costly, like the high costs of operating the system and poor plant health, but they are also dire, like the cavalier use of humanity's second most essential resource for existence — water. An irrigation system is vastly more complicated than plastic sprinklers and valves, connected to PVC pipe, that squirt water around the landscape. Simply screwing sprinklers onto PVC pipe, burying them in the ground and then having the sprinklers pop up, spray water, and pop back down does not mean that the sys- tem is performing adequately, let alone optimally, for the plants. But this is the typical assumption. In fact, the design, construction and management of an irrigation system is a complex blend of multiple sciences — mechanics, physics, electronics, hydraulics, agronomics, horticulture and soils. The average irrigation water use for residential properties is between 2,000 and 5,000 gallons in one irrigation cycle. If a system is watering two to three times per week, it is applying 6,000 to 15,000 gallons of water. Multiply that by four weeks per month, and the monthly water use is 24,000 to 60,000 gallons, or the equivalent to the amount of water in 1.5 to 4.5 swimming pools. MISSING ELEMENTS Studies show the degree of water waste, both residentially and commercially, to be on the order of 30 to 50 percent. While the cost of this resource waste is financially impactful and socially irresponsible, what it is doing to the very plants the water is meant to help also drives up the costs incrementally. At the very core of the high water waste is that many irrigation systems are missing elements when they are constructed, and very few know it. The following are the 7.5 elements that every irrigation system should include if it is to be complete: 1. Sprinklers watering landscape beds and turf are on separate zones (valves). The frequency and the amount of irrigation required for healthy plants and soils in turf areas can be very different from what is required for landscape beds (trees, shrubs and ground cover). Irrigation that is applied when not needed is the very definition of wasted water. Therefore, it is imperative to control the timing of water application, and this can only be accomplished with separate zones for turf and landscape beds. 2. Rotating sprinklers and spray sprinklers are on separate zones (valves). On average, rotating sprinklers apply water at rates approximately 0.30 to 0.80 inches per hour compared to spray sprinklers with a rate of approximately 1.2 to more than 2.0 inches per hour. Both are good products, but it is important to know that sprays apply water three to five times faster than rotors or rotators. Installing rotors or rotators on separate valves (zones) from spray sprinklers allows the sprinkler types to be timed to match the different outputs of water. 3. Operating pressures of the sprinklers are as close to the manufacturer's recommendations as practical. Manufacturers design nozzles for sprinklers to operate within a specific range of pressures (psi). However, there is only one optimum pressure for any sprinkler — the manufacturer's recommended pressure. The closer to optimum performance, the better the chances are to avoid poor coverage (wet or dry areas). The water source and the piping system, along with sprinkler and nozzle selection, must be adequate to ensure the sprinklers are operating as close to optimum pressures as practical. 4. Sprinklers are installed in corners and spaced to overlap each other. All manufacturers design all sprinkler nozzles to provide the most uniform coverage when overlapping each other. This requires that sprinklers be placed in all corners and are arranged so that they throw water all the way to the sprinklers next to them and across from them. The overlap does not have to be perfect, but without sprinklers in the corners, the areas in the corners will not receive the same amount of water as the rest of the irrigated areas. The sprinklers will have to run longer to compensate, making the middle areas The Complete Landscape Irrigation System ILLUSTRATION ABOVE ©ISTOCKPHOTO.COM/SMARTBOY10 ■ BY KURT K. THOMPSON The essential 7.5 elements that every irrigation system should have