Irrigation system audits

Sprinkler System Audits

By John C. Fech

Auditing. Whether it is a bank audit, a tax audit or a sprinkler system audit, the premise is the same: something is not exactly the way it should be. As such, it’s understood that nobody expects perfection in any of these systems, but it’s still important to strive for it. In the world of sports fields, the assumption is that your sprinkler system is broken; the question is just how badly? 

The “just how badly” question is best answered by asking other questions:

  • How many components are not functioning well…or at all?
  • Are there dark green sections of turf next to brown ones?
  • Is it 60%, 70% or 80% efficient?
  • How uniform is the distribution of water?

These questions make some sports field managers grimace and others to shrug their shoulders as if to say, “I don’t know, I’ve never checked into it.” 

Percentages vs. gallons

Percentages of efficiency are one thing, but gallons saved are HUGE! If a significant percentage increase in overall efficiency is achieved as a result of an audit and subsequent repairs, and that improvement is touted to a field stakeholder or decision maker, the response is likely to be “that’s nice” or “good for you.”  However, if the percentage increase is followed by a corresponding reduction in water usage, as well as a cost savings for less applied water, then the response is likely to be more along the lines of “Holy Cow! That’s amazing! Keep up the good work!”  

In order to achieve the second response, start by finding out how many gallons it takes to water the field, then how much can be saved over a year’s time by auditing, repairing and rechecking water usage. Considering the total square footage, the calculation could be in the millions of gallons.

Beyond cost savings

Sure, money talks; but it’s not only about money. There are several other considerations that are compromised with an inefficient system including increased disease potential, pest control failures and even sink holes.

Irrigating for the brown spots

Once you do the deep dive that this article is calling for, you’ll find out just how out of whack the system is. Certainly, older systems with worn parts and old technology can be improved, but even new parts “right out of the box” can be significantly flawed. This begs the question, “How did the efficiency get to be so bad to begin with?” The answer is that we tend to irrigate for the brown spots. It is a basic human tendency to run a system until all the turf areas respond by turning from brown to green. 

Under this routine, the brown spots will eventually turn green. However, in so doing, the areas that are currently receiving the correct amount of water or excessive water will end up receiving two to three times as much water as they need, resulting in a waste of water, root rot and unnecessary expense.

Pest control interactions

Not only is an inefficient system problematic because it’s not keeping the roots evenly moist, but it will also cause a problem with the control of turf insects and diseases. For example, many turf pest control products such as imidacloprid and azoxystrobin need to be watered off of the turfgrass blades and into the upper soil layer to be effective. If the sprinkler system delivers half as much as needed, or three times as much as needed, the product may not be adequately moved into the root zone – being held tightly by the thatch or possibly moved beyond the active root zone by excessive amounts being applied.

Sometimes it’s obvious; sometimes not

Collection cylinders and tuna cans work equally as well in the auditing process. Photos by John C. Fech

In some cases, sprinkler system problems are easy to spot. Leaking heads and valves produce greener turf than surrounding areas, while low pressure output tends to create symptoms of a doughnut pattern. Soggy patches that are not supposed to be soggy are also obvious.  

Some system flaws are not that evident – at least at first. These include clogged nozzles and excessive pressure that produce symptoms that can be confused with other turf maladies and causes such as overly thick thatch, soil compaction, uneven fertilizer application and inadequate seeding rates. The only method to determine if the sprinkler system is causing problems is to audit.

What’s broken?

There are a lot of individual parts in a sprinkler system, each with the potential to work inadequately for various reasons. Here’s a quick rundown of some of the parts that could be in need of repair:

  • Pressure (too high or too low). As mentioned, high and low pressure can cause big problems. A pitot gauge can be placed in the water stream to check for the current pressure amount.
  • Heads that turn, but don’t follow the pre-set pattern. When misaligned, quarter pattern heads can turn into 360 or 180 patterns. They usually just need to be replaced or adjusted.
  • Heads that don’t turn at all. Heads often become sufficiently worn that they simply stop turning. When this occurs, a lot of water is delivered to one part of the spray pattern and not much in the rest.
  • Geysers. When the nozzle is completely missing due to vandalism or old age, an enormous amount of water is blown straight into the air, resulting in a lack of adequate coverage. Needless to say, a great percentage of the applied is wasted when geysers occur.
  • Bent risers. When risers are installed properly, they can withstand quite a bit of abuse from players and field maintenance equipment. However, when they are past their prime operating efficiency or installed a bit on the high side, they can be easily damaged. Bent risers deliver twice as much water on one side of the spray pattern as the other, a result of not delivering water at the correct angle.
  • Low risers. When installed too deeply in the soil or the water pressure is too low, it’s common for risers to fail to rise above the turf canopy. When this happens, they spray water into the grass blades rather than above them.
  • Leaks. When there is a crack or leak in the piping, water seeps out into the surrounding soil, causing it to be wetter than normal. The initial response is healthy, dark-green turf as water stress is being avoided. Over time, however, the result is root rot, as roots need oxygen to thrive.
  • Clogged orifices. Sand, grit and other debris can get stuck in the emitters or orifices, where they can make the opening smaller, and significantly distort the spray pattern. Clogs are usually only evident when audit results are reviewed.

Two step and three step

Catch cans in place.

An audit can be as simple or as complex as you want to make it, or need it to be. So, what’s the basic procedure? Generally, it can be thought of as a two- or three-step process, depending on how you count or how you look at the overall procedure.

The first action is to turn the system on and watch it run, focusing only on the appearance of the water being applied. This is extremely valuable and visual, and is probably the most valuable part of the audit. The initial phase involves making repairs for obvious needs and gross observations that really stand out. The second phase gets to the real heart of the matter, involving measurement of water output and adjustments based on the outcome, while the third is a fine-tuning of the system.

It’s prudent to get started with step 1 by locating the part of the field(s) that is most concerning, and running the zones that cover the area for a short time – 10 minutes or so (long enough to make the observations). In many cases, two to three zones may contribute to a problematic area. While they are running, make a quick sketch of the field and write in general noes such as “east head near 10-yard line not turning,” or “geyser on west sideline.” These problems can be taken care of right away before proceeding with the rest of the audit.

Step 2 is more involved, and takes advantage of the opportunity to determine how effective the first round of repairs were. Begin this step by setting out collection cylinders in the irrigation spray pattern of each head, using the general placement technique of locating one cylinder three feet away from a head and one halfway between heads. Continue placing them until all turf areas are covered. Collection devices can be a bit pricey, but are well worth it. Field managers on a budget can use cat food or tuna cans, which can work just as well as official auditing devices. The dedicated collection cylinders are a bit easier to use, as they have pre-marked water levels printed right on the device (much like a Pyrex measuring cup). 

Once all of the collection devices are in place, run the system long enough to collect about 10-12mm of water. The key intent here is to be able to compare the amounts collected for an initial estimate of evenness of application (a.k.a., efficiency). Simple percentage calculations and averages will suffice. At this point, looking for large differences is also instructive. For example, if catch can A has 15mm of water in it and catch can B has 5, then the deviation is noteworthy and an indicator of inefficiency. The average of 10 in this case is not really indicative of the uniformity of application. Noting the variance is informative, indicating something is broken and needs to be fixed.

Step 3 is best described as a process or protocol: run, then measure, then fix and adjust. The protocol should be continued until at least 80% efficiency is achieved.  As you describe this to staff members and administrators, it’s helpful to remember the goal and benefits; the goal is for all turfgrass areas to receive the same amount of water, and the benefits (cost savings, healthier turfgrass and increased environmental stewardship) serve as outcomes that are worthy of promotional value for your facility and the sports field management industry in general.

Audit frequently

Although it may not be an “in your face” issue such as Pythium root dysfunction or white grubs, auditing a sprinkler system should be an integral part of sports field maintenance. Once a couple rounds of step 3 actions have been implemented, fine-tuning can take place – such as trying 10% reduction in runtime. The premise with this is perhaps the system can be run for a tad shorter time and still achieve the goal of keeping the roots moist. For example, if a zone is set to run for 30 minutes, can it be shortened to 27 minutes – a 10% reduction – and achieve the same results? Considering the price of water in some localities, it is worth the experiment. The prescribed frequency of an audit procedure is field sensitive, but scheduling each field for once per season would be ideal; once a year is considered a minimum.

John C. Fech is a horticulturist with the University of Nebraska-Lincoln and certified arborist with the International Society of Arboriculture. The author of two books and more than 400 popular and trade journal articles, he focuses his time on teaching effective landscape maintenance techniques, water conservation, diagnosing turf and ornamental problems, and encouraging effective bilingual communication in the green industry.