These are thirsty times, and from all indications, they’re going to get thirstier. If you live in a drought area, you already have a taste of what this is like. Water conservation and watering efficiency are the watchwords of the day.

Therefore, as a professional landscape irrigation contractor, you may increasingly be asked to perform water audits. If you or one of your employees is a Certified Landscape Irrigation Auditor (CLIA) as per the auspices of the Fairfax, Virginia-based Irrigation Association (IA), or otherwise certified by your state or other officiating body, you can go ahead and perform them.

A full-blown water audit, depending on the number of zones that need to be tested, can take several hours, and can be expensive for the client. It’s an involved, multi-step process that takes into account a number of factors, including soil type, sun exposure, evapotranspiration (ET) rates, and includes some math formulas.

The math is used to determine the precipitation/application rate of the sprinklers, and the overall distribution uniformity (DU). The end result is a watering schedule that will give the customer the most efficient irrigation for the turf and plant material in his landscape.

But before you start laying out catch-cans, ask yourself if this is what the customer is really asking for, or even needs. When the goal is simply to cut the amount of water used, along with the water bill, is it always necessary to go through all of these steps? The answer is no.

When is an audit not really an audit?

According to Brent Q. Mecham, the IA’s industry development director, there are several terms that get used interchangeably, depending on the region of the country you’re in. Sometimes a ‘water audit’ is called an ‘irrigation inspection,’ ‘irrigation survey,’ or ‘irrigation system evaluation.’ “This could mean, ‘Let’s turn on all the sprinklers, make sure they’re placed in the ground correctly and working right—not spraying off-target—and all the water is going where it’s intended to be,” Mecham says. “They may not necessarily need a catch-can test for this.”

The real reason for an audit needs to be established up-front. A good reason is when you want to identify places where improvement is needed. Ideally, two audits are conducted: the first, to discover the problems; and the second, to reevaluate the system after the corrections have been made.

“Sometimes, you’re having challenges or problems with a site, and you’re trying to figure them out,” says Mecham. “So you do the catch-can test, but not necessarily in every zone, just in the troubled areas, so you can figure out why they’re troubled.”

You might have to do a formal audit because it’s mandated. In some parts of Colorado, for instance, there are ordinances that specify minimum performance levels. No certificate of occupancy will be issued for any property with an irrigation system until a certified auditor verifies that it’s operating to those specifications.

“Picking off the low-hanging fruit”

According to Craig Borland, CLIA, a senior customer resources specialist at Toro’s Riverside, California-based irrigation division, you often don’t need to place catch-cans to see what’s wrong with a system.

“You just turn the system on, and you can see full-circle nozzles throwing water on the side of a building, or half-circle nozzles watering sidewalks or patio areas.

They may be using nozzles with the wrong shapes or the wrong arc adjustments.”

In drought-stricken Austin, Texas, watering is allowed only once a week, in two five-hour windows, morning and evening. Austin Water, the city’s utility, has instituted a tiered-rate structure.

Reaching a higher tier can bring tears to a customer’s eyes when he gets a look at that bill.

When customers want to lower their bills, David Turnage is one of the people who gets the call. A conservation-program specialist at Austin Water, he conducts free system evaluations. But it’s not a formal audit.

“We just go to their homes and show them where the problems are. We focus on high pressure, overspray and runoff—the things that get people warnings or fines. Customers are often amazed to discover they’ve been putting 50,000 gallons of water into their landscapes.”

Turnage and his colleagues identify other efficiency issues, such as clogged nozzles, heads that aren’t standing straight up, are pushed down into the soil or are otherwise low or obstructed.

Very often, what they see is a 12- zone system at a house running 30 minutes per zone. The system will be all spray heads, some irrigating shady turf, some watering turf in a heat island, and some, spraying shrub beds and ground covers.

“These are the customers with the high water bills,” Turnage says, “using 80,000 to 100,000 gallons a month, every month. Those are the people we want to get in front of. Our goal is water conservation; theirs is saving money.”

Many irrigation contractors don’t do catch-can tests or any calculations. They simply walk a property and look for the ‘low-hanging fruit’—obvious things like broken heads, water running off into the street, wet walls, clogged heads, misting and overspray.

They fix the broken heads, change sprays to rotary nozzles, put in ET-based smart controllers and rain sensors, and cut down the runtimes. These things can save just as much water, or more, than doing a full-blown audit and getting a precise watering schedule.

The same is true for commercial properties. Don Blackwell, CLIA, owner and president of Advanced Irrigation, Inc., in Seattle, Washington, offers this example.

“I did a huge audit for a big commercial-use campus. The managers drove me around this complex for an hour. Afterwards, they asked, ‘Do you think you can help us?’ and I said, ‘Well, I’m pretty confident I can save you at least 30 percent.’ Then one of the guys says, ‘How do you know that? You didn’t even get out of the car!’”

“I said, ‘You don’t have a single brown spot in any of your lawns. There’s no system that applies water that perfectly. I can assure you that you’re overwatering by a massive amount.’”

One irrigation expert who speaks at events says he regularly gets asked, “How can I save water?” Before he gets into any of the technical aspects, he asks, “How many of you here want to save your customers ten percent on their water bills, starting tomorrow?” Everyone raises their hands. Then he says, “Tomorrow, go and turn the runtimes on their controllers down ten percent. Neither of you will notice any difference in their landscapes.”

Easier methods

There are some shortcut methods that will give you results very close to what a formal audit would give you. One of them was developed by Stuart Eyring, CLIA, president of Salt Lake City, Utah-based Hydro- Rain.

It’s called the ‘Irrigation Audit App.’ He developed it to make irrigation auditing accessible to a broader range of people, and to increase the amount of audits done overall. The app is free, and can be downloaded from Hydro-Rain’s website.

Since we first reported on it, in October 2014, the user interface has been tweaked a bit to make it even simpler to use. “We designed it under the assumption that if we made the app easy enough, that would equate to a higher level of usage,” said marketing director Kim Hayes. “Twenty-five thousand people have downloaded it, and at least 12,000 audits have been performed using it.”

The app does the math for you. The ET has been computed for you as well, for all land masses of any meaningful size, worldwide. Contractors who’ve used it say that the precipitation rate and DU numbers come out very close to those obtained by the traditional method.

Borland likes another technique. “Lately, I’ve been using the water-budgeting formula specified in California AB 1881 (the Water Efficient Landscape Ordinance, passed in 2009).”

“It’s a simple formula, where you take the square footage of the irrigation area and multiply it by the ET factor for the plant material you’re working with, and multiply that by 0.62. (0.62 is a conversion factor for turning square feet, or inches, of water into gallons.) Then you divide that number by the actual amount of water you used. You get this by looking at the water meter, or calculating what your zone flow is.”

The EPA has something called a WaterSense Water Budget Tool. However, it’s not really an auditing method. Rather, it’s intended to serve as a design tool, allowing a professional to create sustainable landscapes based on a regionally appropriate amount of water.

A lot of contractors have their own ways of doing audits. They’ve figured out on their own what works and what doesn’t, based on common-sense observations. They may do the calculations for DU and precipitation rates, but they don’t go through all of the steps of the traditional method.

Kurt K. Thompson, CLIA, irrigation director at Orlando, Florida-based Massey Services, Inc., is one of the people who developed the IA’s CLIA program. He’s come up with a way to estimate DU using a system of weighted rankings based on sprinkler pressures, spacing, nozzles and conditions. These are then compared to the target uniformity of the types of sprinklers used. (You have to determine the target uniformity number yourself).

He then measures how close the actual water pressure is to the optimum pressure the manufacturer designed the sprinkler for. Next, he looks at the nozzles to see if they are correct for the pressure and the spacing. Then he measures the spacing to see if it’s correct for the nozzles and the pressure. Lastly, he looks at the condition of the sprinklers (are they broken, misaligned, etc.).

Each of the four findings has a numerically-weighted ranking, based on the table shown below (actual numbers are not shown in the table). The four numerical rankings are multiplied together with the target uniformity to get the estimated uniformity.

“We’ve used this method, and then performed a full-on audit with a catch-can test afterwards,” says Thompson. “We’re within a couple of points of it almost every time.”


• Residential Rotors = 0.70 Target Uniformity

• Optimal Pressure = 45 psi, Measured Pressure = 40 psi. Pressure is within 20%, ranking is 0.94

• Optimal Nozzle (for pressure and spacing) = 1.5 gpm, Actual nozzle is 3.0 gpm, Nozzles are incorrect, ranking = 0.9

• Optimal Spacing (based on pressure and nozzles) = 30 feet, Actual Spacing = 34 to 38 feet, Spacing is GREATER than 10%, Ranking = 0.85

• Actual Condition = level, adjusted, not broken, Condition is Good, Ranking = 0.95

• Therefore: Estimated Uniformity = 0.70 x 0.94 x 0.90 x 0.90 x 0.95 = 0.5061 = 0.51

The formal audit procedure

What does a formal irrigation audit consist of? You begin with a thorough inspection of the site. Then you pick out an area to test that looks like it’ll give you a good, average representation of the entire landscape. You’ll then lay out a minimum of 24 catch-cups, in a grid pattern, at fixed distances from the irrigation heads.

The catch-cans should be placed 12 to 24 inches along the edges of each zone, within two to three feet of each spray head or rotor. Then, depending on which type of head you’re testing, you need to place more catch-cans at the points that lie halfway, one-third or one-fourth of the distance between each head.

That’s for even-shaped areas; there are different spacing requirements for unusual or irregularly-shaped areas.

If there are multiple zones, the run times for each must be adjusted to achieve a matched precipitation rate across the test area. The volume in milliliters should be approximately one and one-half times the ‘throat area’ of the catch device in square inches. If that’s 20 square inches, the average volume of water should come out to be 30 ml. (The actual equation: 20 x 1.5 = 30).

You can use information from one zone and apply it to another when there are a lot of identical zones; i.e., the same sprinkler heads, nozzles, spacing and operating pressure, and if they are irrigating similar soil and plant types.

Next, you’ll need to document and record:

• All the sprinkler head locations and their head spacings, the sprinkler makes, models and nozzle sizes,

• The approximate locations of each catch-can and their readings, the runtimes,

• Water-meter readings—if available,

• Pressure readings with locations,

• Wind-speed readings,

• Soil types and root-zone depths,

• Date and time of the testing.

Now comes the math-intensive part, the performance calculation equations. Here you’ll determine the precipitation rate and distribution uniformity. You’ll determine the watering schedule from that.

In conclusion

There is a time and a place for a formal water audit. “I’m a big fan of auditing,” said Blackwell. “It’s a great tool.”

“The disappointment with the auditing process comes in the longterm application of the results.

You’ll audit 100 zones on a site, and you drive by two years later and see water still running down the curb. Nobody’s using that information. There was no long-term commitment to change.”

Irrigation auditing is a valuable tool. Whether you follow the traditional path or take a shortcut, if the destination is greater efficiency and conservation of a precious resource, it’s a journey worth taking.