Bent risers won’t deliver uniform distribution.

The turf in the end zone on the north end of the varsity game field doesn’t look so good. Your mind races with possible causes; after all, this is an important, high-visibility area, not like the practice field. Could be soil compaction or wear damage, although not likely, because the team doesn’t spend that much time there, they’re not that good. Experienced sports turf managers know that over a dozen causes are plausible, now it’s a matter of figuring out which one is responsible.

An insect infestation or a disease infection are possibilities, or maybe it’s not a pest at all. It might be a poorly aligned sprinkler system. The tough part of this problem is that you can’t fix what you can’t see. Even if you can see it, you can’t see it well enough to fix it. There’s usually no way to tell a bad sprinkler pattern from a good one simply by watching it run.

Pest control interactions

Not only is an inefficient system a concern because it’s not delivering the proper amount of water to every part of the field, it will cause problems with the control of insects and disease. Many control products require that the active ingredients be watered into the turf to be effective. If the sprinkler system delivers twice as much as it should in some areas, the effect may be a dilution of the product or movement below the root system, resulting in pest control failure. Likewise, areas that receive half as much water as desired may suffer because the product was not adequately moved into the rootzone by the irrigation system.

Irrigate for the brown spots

When reaping the benefits of automatic irrigation, a basic human tendency is to “irrigate for the brown spots” – to run a sprinkler system until all turf areas respond by turning from brown to green. If the system is not operating efficiently, the brown spots will eventually turn green, but in doing so, the areas that are currently receiving the proper amount will receive twice or three times as much as they need, resulting in wasted water, unnecessary expense, root rot and various other disease problems.

Your system is broken

When I work with homeowners, I draw attention to the importance of the issue by making the bold statement/bet, “I’ll bet any of you $100 that your sprinkler system is broken.” At first, some of them start to think: “Hey, this guy is off base. What a great way to make a quick $100.” That is until I continue with my presentation and outline all of the possible flaws in their system, and then one by one they realize that the assertion is correct. Thinking better of it, they keep their hands down as if they were at an auction not wanting to get called on by mistake by the auctioneer. In over 10 years of making this offer, I’ve only had one gentlemen try to take me up on it. After about two minutes of questioning, he decided that his system was broken, just like all the others.

The only way to know how well this head functions is to audit.

Sometimes it’s obvious

Certain sprinkler system problems are obvious. Low-pressure output tends to produce symptoms of a doughnut pattern in the turf, while leaking heads and valves produce greener turf than surrounding areas. Some system flaws are not that overt, however. Problems such as overly high pressure and clogged nozzles produce random symptoms that can be confused with many other turf maladies, such as excessive thatch, nonuniform fertilizer application and soil compaction. The only way to determine if the sprinkler system is contributing to the demise of the turf is to audit.

Measurement with pre-marked, graduated collection devices.

What’s broken?

Here’s a quick rundown of some potential problems:

  • Bent risers – If a turf utility vehicle tire mistakenly runs over a properly installed irrigation head, there are usually no resulting ill effects. However, if the riser is slow to close when it is struck, or it’s installed a bit on the high side, the potential for damage is high. Bent risers don’t deliver water at the proper angle, resulting in too much on one side and not enough on the other.
  • Risers that don’t rise above the turf – When risers are past their prime or the water pressure is too low, it’s common for them to fail to rise as high as they should. When this occurs, they deliver water in the turf canopy rather than above it, resulting in poor coverage.
  • Leaking heads and pipe connections – When there is a crack or leak in the piping, water seeps out into the surrounding soil, causing it to be wetter than normal. This often results in darker than desirable grass or root rot.
  • Pressure: too high or too low – As mentioned previously, low and high pressure cause problems of inefficiency. A pitot tube can be used to check for proper pressure.
  • Heads that don’t turn – Heads that are worn so much that they no longer turn deliver too much water in one part of the pattern and none in the other.
  • Heads that turn but don’t follow the preset pattern – Quarter patterns can turn into 360-degree patterns if they become misaligned; they simply need replacement or adjustment.
  • Clogged orifices – Sand and other debris can become deposited in the emitters/orifices, where they significantly distort the spray pattern. These problems usually require auditing to become evident.
  • Geysers – When the nozzle is completely missing due to vandalism or age, lots of water is wasted, and a lack of adequate coverage occurs. Geysers are most common on low-visibility areas or low-use fields, where they are noticed less often.

Two-step and three step protocols

Auditing a sprinkler system is a two-step process. The first step involves making gross observations and repairs for obvious needs. The second involves measurement of the water output, repairs and adjustments based on the outcome, and a fine-tuning of the system.

Get started by locating the part of the field that is most concerning and run each zone that covers it for 10 minutes. In some cases, parts of three or more zones may contribute to the problematic area. While each zone is operating, make a quick sketch of the field and write in general notes. If obvious problems exist, make the necessary repair or adjustment.

Next, take the opportunity to determine how effective the first round of repairs were. Set out collection cans in the irrigation spray pattern of each head by placing one 2 feet away from a head and another halfway between it and another head. Continue until all turf areas are covered by collection cans. Fortunately, collection cans are inexpensive; my favorites include empty cat food and tuna cans. Of course, official irrigation auditing devices are available, and may be a better choice if your boss is watching. However, each will deliver the necessary information about irrigation efficiency.

Once the collection devices are in place, run the system again for 15 minutes, turn it off, and then measure how much water is deposited into each collection can. Compare amounts for an initial estimation of efficiency. Simple percentage deviation calculations will suffice. For example, if the system deposits 10 mm into can A and can B receives 18 mm, there is an obvious difference that needs to be dealt with. In this case, the deviation from one can to the other is significant, with the turf immediately surrounding can A receiving 55 percent of the water as that which surrounds can B.

This three-step protocol – run, measure and adjust – should be continued until at least 80 percent efficiency is achieved. Overall, it’s helpful to remember that all turf areas should receive the same amount of irrigation water.

Audit regularly

Though most sports field managers feel that auditing their sprinkler system is not the most exciting activity on their to-do list for the month, hopefully this article has shown the importance of audits and the benefits that can arise from doing them. Like any other mechanical system, sprinkler systems benefit from regular inspections to prevent future turf problems. Schedule each field for regular audits; once per season would be outstanding, with once per year at a minimum.

John Fech is an extension educator specializing in turf and ornamentals at the University of Nebraska-Lincoln.