A catch-can test gives you a simple way to compare how much water reaches different parts of a lawn during the same sprinkler cycle. Place matching containers around one zone, run it for a measured interval, and compare the collected depths. The result is a map of relative distribution—not an explanation of why one spot received more or less water.
What the test measures
Each container samples the water reaching one small location. If the containers are alike and run together for the same period, their readings can be compared. A cluster of lower readings may point to a drier part of the zone; higher readings show where more water collected during that test. The numbers describe that cycle and setup, rather than every condition the lawn experiences.
Test one zone at a time. Sprinkler systems often divide a property into zones with separate operating schedules and different head arrangements. Combining containers from zones that run at different times would not make a fair comparison.
Set up a fair comparison
Use identical, open containers that can collect water without tipping. Spread them across the area served by the zone, including near its edges and in spaces between sprinkler heads. A few cans grouped in one convenient spot may miss a dry strip elsewhere, so think of placement as sampling the whole zone rather than checking a single sprinkler.
Choose a consistent, measured run time for every container in that test. Start the zone, allow the cans to collect water through the same cycle, and stop the test together. Record the duration so a later comparison has context. If the run is interrupted or the conditions change substantially while you are observing it, the readings may not represent comparable exposure; note that rather than treating the figures as precise measurements of a typical day.
A simple sketch helps. Mark the approximate sprinkler heads, lawn edges, and locations of the cans. Label each container on the sketch before measuring, so the recorded depth remains tied to where it sat. This need not be a scaled drawing; its purpose is to preserve the relationship between each reading and its place in the zone.
Compare the collected amounts
After the cycle, use the same ruler or measuring tool to read the water depth in each container. Write down the value beside that container’s map label. Read all cans in the same way and compare their depths; avoid relying only on which one looks fullest, because perspective and container shape can be misleading.
To quantify the spread, subtract the lowest collected depth from the highest and note the difference beside the map. For example, readings of one-quarter inch and one-half inch are one-quarter inch apart. This makes the contrast easier to compare across locations or in a later test.
For example, imagine a hypothetical rectangular lawn with cans placed along the perimeter and between heads. If most readings are similar but two neighboring cans near one corner are lower, mark that corner as a localized difference. If readings are low throughout the map, record the broader pattern instead.
Use the pattern to choose what to inspect next
Compare low and high readings with what you can observe during a normal sprinkler cycle. Note whether a head appears blocked, whether its spray reaches the mapped area, or whether an object or landscape feature lies between the head and the low-reading location. Record what you actually see separately from your interpretation.
A later test using the same container positions and run time can show whether the pattern recurs. If the same locations repeatedly collect less water, focus your next inspection on those areas and the spray reaching them.
For local directory details, see Charlotte Irrigation.
