Catch-can audit · uniformity · scheduling · client report
Run an irrigation audit in your browser
An irrigation audit measures how evenly a sprinkler zone applies water (distribution uniformity) and how fast (precipitation rate), using catch cans set across the zone during a timed run. From those two numbers this tool computes a corrected runtime, splits it into a cycle-soak controller program your soil can absorb, and prices the water saved. Data stays on your device.
New to the method? Start with how to run a catch-can test, then check your DU against the targets by head type.
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What the numbers mean
DU low quarter
The average of the driest quarter of catch readings divided by the overall average. It is the auditor's headline number because plants in the driest patch set the schedule: a DU of 60% means the zone must run roughly 1.67 times longer than perfect coverage would need.
Christiansen CU
An older uniformity measure based on average deviation from the mean. It weighs wet and dry spots equally, so it always reads higher than DU on the same data. Reported alongside DU because some specifications still cite it. DU vs CU explained.
Precipitation rate
Inches of water applied per hour, measured as mean catch depth divided by test runtime. With the weekly plant need it fixes the total minutes; with the soil intake rate it fixes how long each cycle can run before water starts running off. Typical PR ranges.
How the audit flows
- Add each zone with its area, head type, and current weekly runtime.
- Run the zone for a timed interval with catch cans out, then enter the readings in inches or mL.
- Read the DU, CU, and precipitation rate, graded against head-type expectations.
- Set the weekly need, watering days, start times, and soil to get a cycle-soak controller program.
- Print the client report with the savings estimate, or export CSV and JSON.
Frequently asked questions
What is an irrigation audit?
A field measurement of how evenly and how fast a sprinkler zone applies water, done by placing catch cans across the zone, running it for a timed interval, and reading the collected depths. The results (DU, CU, and precipitation rate) drive a corrected watering schedule and a defensible savings estimate.
How does Irrigaudit calculate distribution uniformity?
DU low quarter is the average of the lowest quarter of catch readings divided by the overall average, times 100. The low quarter counts floor(n/4) readings with a minimum of one. Christiansen CU is also computed, using the average absolute deviation from the mean.
Can I enter catch readings in millilitres?
Yes. Switch the catch unit to mL and enter the device throat area (or a throat diameter, and the area is computed). Each reading is converted to inches of depth as volume divided by throat area before any statistic is computed.
How are the water savings calculated?
Gallons are area in square feet times depth in inches times 0.623, where depth comes from the measured precipitation rate and the runtime. The tool compares the current schedule with the recommended one over your irrigation season at your water rate. The result is an engineering estimate with stated assumptions, not a utility-bill guarantee.
Is my audit data uploaded anywhere?
No. Zones, catch readings, photos, and saved audits live in your browser's local storage on your device. You can export a JSON backup or CSV at any time, and restore the backup on another machine yourself.
Is Irrigaudit free?
The single-zone audit calculator, guides, and reference tables are free with no account. Some workflow features are part of a paid tier when billing is enabled on this site.