Increase in sprinkler-head longevity
A term you commonly hear in the vernacular of lawn-care professionals is "mower bait." This is how operators refer to sprinkler heads that are incorrectly installed and in the direct path of their mowers. It is obvious that in such a confrontation, a sprinkler head is no match for a mower. The end result is another scar on the side of the mower and increased maintenance costs to the property owner.
However, this is not the only way that sprinkler heads are susceptible to damage. Freeze damage and vandalism also account for losses. While many landscapers feel the replacement cost of a sprinkler head is insignificant, nothing could be further from the truth. The following factors indicate the potential cost--most of it to the client--of sprinkler-head damage:
* If the damage goes unreported, the amount of water that discharges from the broken head can be substantial. Keep in mind that the client often pays for water by the gallon.
* If the head is broken and the system leaks water, the rest of the irrigation zone will not function properly, possibly damaging the rest of the landscape.
* If leaking water wets a public walkway or road, it creates a liability issue.
* If the maintenance contractor is not aware of the damage, or not contractually liable for the damage, the client must pay for a service call for an irrigation contractor to make repairs.
Additionally, if you replace the irrigation head with a different type of sprinkler, other problems will follow. A well-designed sprinkler system is based on a specific type of sprinkler head that will perform in a predetermined way. Typically, when a sprinkler head is damaged, the contractor replaces it with either the least expensive product or whatever sprinkler head happens to be on the truck or in inventory. The problem with this is that the new head may not be compatible with the existing systems' design and can decrease the efficiency of the irrigation system.
Obviously, then, you should replace broken sprinklers with the same head, if possible. However, the best way to avoid these problems is to prevent them in the first place--design, install and maintain sprinkler heads so they are not vulnerable to damage from vandalism, mowers or weather-related problems.
Precautionary hardware When designing an irrigation system, designers consider a multitude of factors. These range from determining safe water-flow rates to the hydraulic performance of the system. However, of all the components in a sprinkler system, the sprinkler head is the most important part. The sprinkler head determines the ultimate performance of the system and is the component that actually distributes the water. Because they are the key to the irrigation system, you should take specific steps to protect sprinkler heads. Two pieces of hardware can prevent much of the damage sprinklers experience:
* Automatic drain valves. In areas where temperatures routinely fall below freezing, you should install a series of automatic drain valves in each zone of irrigation. These valves, installed below heads and at low points in pipe lines, release water when the system is not running. Thus, when freezing temperatures strike, frozen water cannot burst your pipes or other components. When installing these drain valves, keep in mind that you should install them with a "tee" offset at a 45-degree angle and draining into a gravel sump (see figure, below right).
* Swing joints. The best way to protect a sprinkler head from physical damage is to design and specify the use of what is commonly called a swing joint. A swing joint is a series of fittings arranged in such a way that they allow the sprinkler to move with a three-dimensional range of motion. This 3-D range allows the sprinkler head to move in any direction without breaking, even though it is attached to rigid pipe. It can then survive being overrun by vehicles or grounds equipment, or an impact from a vandal. The swing joint literally moves or swings out of the way when objects such as vehicles, mowers or carts impact the sprinkler. By swinging out of the way, it avoids damage to either the sprinkler head or to the piping structure to which the sprinkler head is attached. At worst, the impact may knock the sprinkler out of alignment, but this is much better than a broken sprinkler head or pipe.
The term "swing joint" is a common term used in the industry. However, several different types of swing joints are available. A true swing joint (see photo, below left) has three different 90-degree elbows that allow the sprinkler head to rotate in a complete three-dimensional range. This way, regardless of the angle of impact, the sprinkler head can rotate or swing out of the way and not cause any damage to the sprinkler head or the pipe. This type of swing joint generally is pre-manufactured and available from several companies.
Another common type of swing joint consists of a section of flexible pipe with elbows or fittings at either end (see figure, above left). This works in much the same way as the 3-D swing joint does. However, it is the flexible pipe that provides most of the movement rather than the elbows. Several manufacturers produce flexible swing joints and parts, and they are less costly than true swing joints. However, installers commonly build their own flexible swing joints, as well.
If you decide not to use a swing joint of any kind, you should at least install the sprinkler head on a flexible or semi-rigid riser or nipple. That way, in the event of an impact, the riser or nipple will break instead of the pipe.
Proper installation There is an axiom in the irrigation industry--"Measure it with a micrometer, mark it with a crayon and cut it with an ax." This, unfortunately, applies to most irrigation systems. The designer may have specified swing joints, but it is still up to the installer to install them correctly.
When you install sprinkler heads, you should always follow some basic guidelines. If you do, the sprinkler heads will enjoy a much longer life.
* Ensure that the sprinkler head is at least 2 inches in from the edge of any curb, sidewalk or other surface you will maintain with an edger. If you place the head directly against the edge, an edger or other equipment will damage it.
* Be sure that the head is clear of any obstructions it could hit if it were to swing as a result of an impact.
* Install sprinkler heads even with the grade level of the soil, not to the level of the turf. If you install a sprinkler head above grade level, it has a high probability of becoming "mower bait" and being cut off or broken.
* When installing a sprinkler head with a flexible swing joint, ensure that the length of flexible pipe cannot kink or crimp. (When you use flexible tubing to make up a swing joint, it is important to ensure the inside diameter of the pipe is large enough to handle water flow to that sprinkler head without exceeding the generally accepted flow rate of 5 linear feet per second.) Install impact rotors (or any type of rotors that have a designed slit or opening in the base) in a gravel-filled sump at least twice the diameter of the irrigation head.
When you look at the evolution of a sprinkler system from its initial design to its installation and use, it is obvious that its most vulnerable aspect is in the maintenance of the system. After you install a system, its maximum performance is fixed according to its design. However, contrary to popular belief, sprinkler heads do require some maintenance. The maintenance of a sprinkler system is a continual process, and if you neglect it, the system's performance will degrade to unacceptable levels. Maintenance procedures address three distinct areas:
* Nozzles. Most sprinklers have a filtration system integrated as part of the sprinkler head or installed as an inserted part. Because spray heads generally have much smaller orifices than rotor sprinkles, they are more likely to come with a filter of some kind. By removing the nozzle, you can gain access to the filter and clean out any trash or debris. Because rotors have much larger orifices, trash or debris that passes through their filters will generally be able to pass through the nozzle as well. Cleaning out sprinkler filters is a task typically performed in the spring of each year.
* Proper alignment. The re-alignment of sprinkler heads is a constant process that you should perform whenever you observe that the heads need adjustment.
* Sprinkler-head height. You should raise or lower the sprinkler heads as necessary to maintain them at grade level. If the heads are on swing joints, this task is fairly easy. If not, it will require you to do some additional work. The raising or lowering of sprinkler heads keeps the sprinkler system operating within the system's design parameters, as well as protecting it from damage.
One of the historical solutions to the problem of a sprinkler head that is too high or too low is to install a concrete "donut" around the head. When swing joints were not available, this might have been a good option. However, because a variety of swing joints is available in today's marketplace, "donuts" are really an unnecessary item. Additionally, they detract from the aesthetics of the landscape.
You can greatly extend the longevity of a sprinkler system if you make a conscious effort to maintain the system's components. The best, most cost-efficient way to do this is to ensure that the design includes adequate protection with swing joints and automatic drain valves. Anytime you need to replace a sprinkler head, use the same head for which the original design called. If the design did not include swing joints, add them as you replace heads. These techniques alone allow systems to withstand most abuses they are likely to encounter. The end result will be a smaller impact on the client's operating costs and better results from your maintenance efforts.
Kurt Hall is president of Innovative Irrigation Technologies Ltd. (Houston).
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