Catch-can audits and irrigation repair diagnosis

Separate symptom from cause

A brown patch can arise from a clogged nozzle, broken riser, wrong arc, insufficient pressure, an obstruction, poor soil, pests, or a mismatched schedule. A continuously wet area can arise from a leak, low-head drainage, runoff, poor drainage, or excess watering. Begin with observations and measurements rather than immediately replace the controller or increase runtime.

Confirm the source is open, the controller is operating the intended zone, and the valve closes when commanded. Inspect the area while running and after shutdown. A steady leak from an off zone suggests a valve or supply issue; brief drainage from a lower head can be the lateral emptying. Check whether an approved check-valve head is appropriate before labeling all post-shutdown water a leaking valve.

Observe pressure and flow. Many weak heads together can indicate source, valve, filter, mainline, or excessive-demand problems. One weak head can indicate a local clog, damaged riser, or branch problem. An unusually high zone flow can indicate a break or missing nozzle. A lower-than-expected flow can indicate obstruction or a closed flow control. Compare with the design and known-good operation.

Arrange a catch-can test

Use equal containers or calibrated collectors in a representative grid over the zone, including edges and suspected dry areas. Keep openings level and unobstructed. Test under suitable wind conditions and a known duration, using the normal operating pressure and configuration. Record nozzle types, arcs, test time, conditions, and each depth.

Average depth divided by duration gives precipitation rate. If average collected depth is 0.25 inch in fifteen minutes, the rate is one inch per hour because fifteen minutes is one-quarter hour. A thirty-minute test with the same depth would give half an inch per hour. Do not divide a depth in inches by minutes and label the result inches per hour without converting.

Catch cans measure delivered distribution at their locations. They do not directly measure infiltration, root depth, or water remaining after drainage. Inspect the soil as a separate step. A uniform collection pattern can still apply too quickly for the soil or fail to wet enough depth under a short schedule.

Low-quarter distribution uniformity

Low-quarter DU is the average depth in the lowest quarter of collectors divided by the average of all collectors. Sort the measurements and select the driest quarter according to the audit method. If sixteen collectors average 0.25 inch and the lowest four average 0.15 inch, DU is 0.15 divided by 0.25, or sixty percent.

This means the driest quarter receives only sixty percent of the overall average, not that sixty percent of the water is necessarily lost. Poor DU can result from pressure, nozzle mismatch, spacing, wind, blocked patterns, or damaged heads. The statistic identifies unevenness; field observation identifies the repair.

If a scheduling method targets 0.50 inch in the low quarter, the example's average application would need about 0.50 divided by 0.60, or 0.833 inch. That extra average depth may overwater other areas, so repair distribution first. Do not repeatedly compensate for a missing corner nozzle by flooding the rest of the lawn.

Diagnose and repair common faults

For a clogged nozzle, isolate water, clean or replace the approved part, flush as directed, and verify the pattern. For a broken connection, repair with compatible materials and required cure, then water-test and restore grade. For low pressure, check actual supply at flow, upstream filters and valves, zone demand, pipe losses, and elevation. A larger nozzle can make a low-pressure zone worse by increasing demand.

A valve that will not close can have debris, damaged diaphragm, a stuck solenoid, incorrect manual bleed position, or a controller command. Separate the electrical and hydraulic causes. Follow the valve manufacturer's disassembly and replacement instructions and do not work on a pressurized bonnet. A valve that will not open similarly requires both circuit and hydraulic checks.

Drip repairs require checking filters, regulators, tubing, emitter flow, and wetting. A plugged emitter does not justify raising the whole zone pressure beyond the product limit. Flush and restore compatible parts, then check representative plants. Preserve potable protection and never bypass a backflow assembly to improve pressure temporarily.

Confirm the result

Repeat the relevant pressure, flow, pattern, or catch-can measurement after correction. Update the nozzle and zone schedule if parts changed, and observe closure after the test. Record what failed and why, not only the replacement part. Give the owner revised settings and maintenance instructions, and inspect soil moisture to confirm that improved distribution produces the intended root-zone result.

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