1) Why the catch cup test matters
A catch cup test converts a “looks fine” sprinkler zone into measurable performance. By collecting depths at multiple points, you can quantify how evenly water is applied and how much runtime is needed. This calculator reports CU and DUlq to highlight both overall uniformity and the driest quarter of the area, which typically drives plant stress.
2) Planning a reliable layout
Use identical cups and distribute them evenly across the zone, including edges and near head-to-head overlap lines. A 4×4 layout (16 cups) is common for medium landscape zones. Run the test during calm wind and stable pressure. Record one depth unit consistently, then paste values exactly as measured to avoid skew.
3) Reading CU and DUlq together
CU reflects average deviation from the mean, while DUlq focuses on the lowest 25% of readings. Higher DUlq usually means fewer dry spots and more efficient scheduling. For many gardens, CU above 80% and DUlq above 70% are practical targets, but rotary, spray, and drip systems can differ. Always compare zones under similar test conditions.
4) Using precipitation rate for scheduling
Precipitation rate translates depth into “how fast the zone waters.” For example, using the sample dataset (mm) with a 30‑minute run, the calculator returns an average catch of about 10.875 mm and a precipitation rate near 21.75 mm/hr. If your weekly requirement is 25 mm, an initial estimate is roughly 69 minutes per week, split into cycles to reduce runoff.
5) Turning results into improvements
When DUlq is low, address hardware and hydraulics before adding runtime. Check clogged nozzles, mixed nozzle types, incorrect spacing, tilted heads, and pressure that is too high or too low. Re-test after adjustments and track CU, DUlq, and SC over time. Small fixes often produce large water savings and healthier turf.