How to Complete an Irrigation Audit

An irrigation audit is similar to an irrigation site survey but goes more in depth and digs into inefficiencies and issues. The deeper your audit is, the better you can recommend the exact treatment and products needed. This is a great way to show customers your expertise and value.

Materials Needed for an Irrigation Audit

• Marking flags to identify sprinkler head locations
• Measuring tape to measure sprinkler head spacing
• Pressure gauge to check system pressure
• Pressure adapter to ensure regular pressure flow
• Stopwatch/timer to capture run time
• 24 (or more) catchment cans with millimeter measurement increments to capture irrigation water
• A way to track your audit, like the EPA’s irrigation audit checklist

Completing an Irrigation Audit

Before running the irrigation system, check that it works properly and complies with all local codes. You’ll need to correct any defects if they arise before running your audit, including any adjustments. Look for system damage and any problems in the yard, like dead spots, obvious sprinkler damage, poor drainage, or controller issues. Consider following the steps of an irrigation site survey before starting your irrigation audit.

Winds should be less than 5 mph for accurate testing. Audits should occur at the same time and for as long as the irrigation system typically runs.

Lay out catchment cans in a grid throughout your zone. There should be a minimum of 24 catchments but including more can give you a more accurate reading. They should be placed at the sprinkler heads and halfway between each head. However many catchments you have, the number should be divisible by 4. Ensure you’re not blocking the spray; move or lower the catchments if blockage occurs.

Map out the zones you are testing. Ensure you measure the size and shape of the area, marking the locations of the sprinkler heads, type and model of nozzles used, spray head arc and radius, and locations of catchments. Measure and record the distance between catchments.

Attach the pressure adapter and pressure gauge to the furthest sprinkler head from the valve. Start your timer as your turn on the zone. While the zone runs, record the pressure reading from the gauge. Continue to run the zone until there is an average of 25 milliliters in each catchment (the catchments should have measurement marks), then turn off the system, stop your timer, and record the run time.

Record the amount of water in each catchment. Sprinkler efficiency is measured in DULQ, or Distribution Uniformity Low Quarter. To find this measurement, add up the total amount of water in all the catchments, then divide the result by the number of catchments you used to find the average amount of water collected. Next, identify the lowest 25% of catchments, regardless of where they were placed in the zone. For example, if you used the minimum number of 24 catchments, identify the lowest six catchments for the 25%. Add up the total amount of water in those lowest 25%, then divide by the number of catchments (in this case, six). Lastly, divide the average from the lowest 25% of catchments by the average from all the catchments to determine the DULQ of the zone.

Traditional spray heads typically have a DULQ of 40-45%, whereas high efficiency nozzles and rotors typically have DULQ’s of 70%. The higher the number, the more efficient the system is. Audits may vary based on type of nozzle used, head spacing, operating pressure, and other considerations.
If the water catchment is below average, distribution is affected. Look at sprinkler location, nozzle performance, and type of sprinkler to see if the correct products are being used. In addition, you may consider increasing pressure. If the water volume is above average, this could indicate excessive pressure, which could damage the entire system. If all the zones have the same heads, spacing, and pressure, you can test half the zones to get the average.

Things to Note

If customers’ have a mixture of sprinkler heads and nozzles, consider changing them to the same brand and model for uniformity and to increase efficiency or using matched precipitation rate (MPR) nozzles. Use the manufacturer data sheets to determine sprinkler and nozzle performance. This would also be an excellent time to discuss switching to a SMART irrigation system if customers run a traditional system. SMART irrigation saves customers water and money, and you can upsell.

Ensure you have all data properly recorded for your notes, as these can help you identify any problems in future jobs, as well as recommend exact solutions for any current issues the system is showing. Give a copy of your audit that includes your recommendations for improvement to your customers, so they have time to review the data. Consider suggesting a maintenance schedule as well in your notes.

Some areas also offer financial incentives to switch to SMART technology, which you can also include in your report.

SiteOne Can Help

If you have any questions on how to conduct an irrigation audit, or need supplies for the job, associates are waiting to help in your local branch. You can also order anything you may need on SiteOne.com or in the SiteOne mobile app.