When the irrigation system is run to perform the test, the same drawing can be used to record the amount of water in each catch can next to the catch can symbol. As a backup, the data should be entered into a table based on the placement grid. The purpose of doing this is to be able to come back later to locate the places that are over-irrigated or under-irrigated. That in turn will help in finding specific steps for making improvements in the system’s performance.
Before running the test, check each catch can to be sure it will properly collect a sample. See that no obstructions are in the way of the sprinkler distribution pattern. In a turf sprinkler situation, one would check to see if the nozzle discharge hit the side of the catch container. One does not want the can to be knocked over. Water should not be deflected from nursery containers, trees or walls. Be sure the wind will not be a negative factor. A wind speed over 5 miles per hours (mph) will cause considerable distortion of the pattern.
Wind Problems. If wind speed is a potential concern, run one sprinkler and measure the wetting pattern on both the upwind and the downwind sides, in feet. Divide the Upwind Distance by the Downwind Distance to get a ratio. If the ratio is less than 0.60, then the wind speed is over 8 mph. This is excessive. For example, if the upwind distance is 51 feet and the downwind distance is 93 feet. Then the ratio is 51 / 93 = 0.55. This is less than 0.60 so the wind speed is over 8 mph. Try to test with the wind speed below 5 mph! Record the wind speed each 5 minutes, if possible, and average at the end.
Testing Run Times. How long should the irrigation zone run to give test data? Allow the irrigation zone to run one normal irrigation cycle. If that length of time is too long then half a cycle may be sufficient.
One suggestion is to run the system until at least 25 ml have been collected. For large sprinkler systems, five revolutions of the sprinkler is a minimum. Record the volume collected and the run time for each sprinkler.
Collection of data. At the beginning and just before the test run is finished, measure the nozzle pressures and flows. For drip lines there is a needle like attachment for a pressure gauge that can be inserted into thinwall tubing to measure pressure. When the test is stopped, note the time on the stop watch of the length of run. Measure the wind speed. Now, one by one retrieve the catch cans and dump the contents into a graduated cylinder to measure the water volume collected. Write this value on the site map for the individual catch can. Later transfer these data to a spreadsheet.
The same person should read the volume of all catch can samples so that the data collection is uniform.