A catch can test is only one of the tests we perform when we conduct a water audit. Many Superintendents and Grounds Managers have the misconception that a water audit consists solely of performing a catch can test. Some think an inventory audit is part of a water audit. An audit can include many elements and is subjective so it's important to understand what specific services an auditor is offering.  If you are looking only for catch can tests then have a specific reason for that service only. A catch can test can can serve several purposes including:

So what does a catch can test really measure?

A catch can test helps measure the health and performance of your irrigation system. The results of the test provide you with the D.U. and a Precipitation Rate (PR). The resulting D.U. indicates how uniformly water is distributed in that given area at a specific point in time. 

Catch cans are typically conical shaped devices placed in a holder which captures water from the sprinklers. The water is measured in millimeters. To calculate the D.U. divide the average low quarter of the cans by the average of all cans. This means that the total quantity of cans should be a number divisable by four. D.U. is expressed as a percentage. The higher the D.U. the more efficient the system is. 

When conducting a catch can test, the collection devices must be spaced evenly in a grid pattern and not placed too close to the actual sprinklers. This  helps avoid water knocking over the cans during the test. It also helps in capturing the water distributed out of the small and medium range nozzles. If a can(s) are too close to the sprinkler, small holes can be cut into the soil and the cans lowered. The pattern can be rectangular, diamond or triangular.  A sufficient run time should be used in order to collect at least 20 millemeters in a majority of the cans. Be careful to not run too many sprinklers on the same lateral at the same time or the results could be flawed due to low pressure on the laterals.

Distribution of Uniformity is an industry accepted mathematical formula which has been developed by Cal State Poly University Irrigation Research and Training Center. By Cal State Poly’s model, an irrigation system is rated based on the following results:

• Excellent -   85% or greater
• Very Good - 80%
• Good -        75%
• Fair -          70%
• Poor -         65% or less

It is my opinion that these percentages are vague and leave room for interpretation by both the auditor and the client. According to my research regarding the establishment of these percentages and performance, they were adopted in the late 90’s. At that time, golf sprinkler technology was not as good as it is today. 

Although a 100% D.U. is theoretically possible on paper, you should not expect these types of results even with a new irrigation system with the same type sprinkler heads and consistent head spacing. A new system should be expected to have a D.U. of 85%. There are so many factors which will affect D.U including, but not limited to: age of system, worn nozzles,low or tilted heads, pressure, wind, rotation times of sprinklers and pump efficiency.

When to do a Catch Can Test?

When Golf Irrigation Consultants conducts a catch can test, we like to conduct the test during the morning or afternoon.  We then leave the cans in the same place and conduct the test during the night under normal operating conditions. Typically we see a higher D.U. during the daytime test when the irrigation system is not in full operation. D.U. is usally 5-10% lower during the night due to higher flow demands or fluctuating pressure during the nightly cycle.

What do all these numbers really mean to a Turfgrass Manager?

As they say information is key to making smart decisions. We understand that at the end of the day, you may need to irrigate enough to ensure that your customers are happy and are playing on green grass. What is important to understand, is that the lower your D.U. is, the longer your run times need to be to keep the turf in a healthy state. Obviously the longer run times equate to the use of more water and higher costs for water. The difference in a D.U. of 75% compared to 85% can equate to spending ten’s of thousands of dollars more in water and electricity each and ever year. 

For more information on a professional water audit coupled with a catch can test, please contact us and we will go over in detail how our services can give you the information you need to make informative decisions 

415-342-1030