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Lawn Sprinklers & Irrigation

2008-04-01 12:10:00

Sprinkler systems on wells - a good idea?

Answer: All lawn sprinkler systems basically operate in the same way: a timer (or clock) activates valves in the yard at specified times to allow water to flow through zones and out the sprinkler heads, thereby watering the grass. The primary difference is where the water comes from. There are two water sources, and each has unique pros and cons. Water wells are prominent in the Wichita area due to the relatively high water table, especially west of the Arkansas River. A well is created by simply drilling a hole into the earth that extends below the water table, then inserting a perforated pipe (well casing) that allows water to flow into it. The vast majority of wells use a submersible pump suspended in the water by a poly pipe to pump water up to the surface and into the sprinkler system. Residential pumps normally have a 1-horse electric motor using 220 volts, and are water-cooled internally by the same water that they are pumping to the system. There are several advantages associated with well water. The cost of the electricity used by a 1-horse pump is significantly less than the cost of city water as the amount of watering increases. Because water exits the well out through the side of the casing, all of the sprinkler piping remains underground. And since no pipes are exposed to the freezing temperature of the air, using a well as your water source safely extends your lawn-watering season into the colder months. One disadvantage of having a well drilled is the up-front cost. Well drilling is priced by the foot, with the pump and other components sold separately. And in some locations, the water is at such a depth as to make drilling cost prohibitive to many homeowners. Additionally, ground water sometimes contains minerals and other elements that can stain siding, fences, driveways, or anything else they come in contact with. Pumps are not compatible with residential drip irrigation used for shrub beds because drip irrigation is a low-volume system, and pumps must pass 4-5 gallons per minute to safely operate. City water sprinkler systems use the same water that all residences and businesses in the community use. The connection point is typically either in the basement near the point that the water line enters the foundation, or outside near the water meter. A valve is installed to turn on and off the water to the lawn sprinkler, and a backflow preventer is inserted between the connection point and the sprinkler components. The greatest advantage for new homeowners using city water for irrigation is the fact that there are no additional up-front costs: the water line to the house is already there. The city water supply is a “known” commodity. There is good pressure, and the water is clean. However, because city water is the public potable water supply, it is regulated by the government. In 1991, the Kansas Department of Health and Environment classified lawn sprinkler systems as a “high health hazard” to the potable water supply, requiring that all such connections be protected by a testable backflow prevention device. The most common is the pressure vacuum breaker (PVB), which effectively stops water entering the city mains from a sprinkler system. Chapter 21.12 of the City Code requires these devices to be tested annually, and rebuilt every 5 years. The PVB must be a foot higher than the highest head on the system in order to function properly, which makes it susceptible to freeze damage. Additionally, the City charges for water use on a tiered system. In other words, the more water a customer uses, the higher the rate charged becomes.