Troubleshooting and System Auditing

Why Troubleshooting and Auditing Matter

An irrigation system that leaks, underperforms, or wastes water costs the client money and can harm the landscape. Technicians who can locate faults quickly and prove system performance with hard data are valued in the field. Two skills define this lesson: fault diagnosis — finding and fixing what is broken — and distribution uniformity (DU) auditing — measuring how evenly water is applied across a zone.

Systematic Fault Diagnosis

Never guess and dig. Work from the top down, zone by zone, using your senses and instruments before you touch a shovel.

Step 1 — Visual inspection. Walk every zone while it is running. Look for heads that are not rotating, nozzles with no arc, puddles suggesting a cracked lateral, dry patches, or flooded spots. A clogged nozzle produces a distorted or absent stream. A misaligned rotor may spray a wall or walk past its intended arc.

Step 2 — Zone-by-zone activation. Use the controller to run each zone individually. Note which zone shows the symptom. A stuck-open valve will allow water to flow in its zone even when the controller has moved on; look for a zone that never fully shuts off.

Step 3 — Pressure gauge readings. Thread a pressure gauge onto a Schrader valve adapter at the head closest to the valve and at the head farthest from the valve. Low pressure at the far head but normal pressure at the near head points to a partially closed valve or undersized pipe. Very low pressure system-wide suggests a supply problem or a major break. High pressure can cause misting and poor distribution.

Step 4 — Electrical check. A zone that does not activate at all despite normal controller commands may have a broken wire or a failed solenoid. Use a multimeter to measure resistance across the solenoid coil at the valve — a reading far outside the manufacturer's specified range (commonly around 20–60 ohms for residential solenoids) indicates a bad coil. Check wire continuity from controller to valve. A broken wire will show an open circuit (infinite resistance).

Step 5 — Document, then repair. Fill in your fault-finding worksheet before you start repairing. Record the zone, symptom, likely cause, pressure readings, and meter readings. Once diagnosed, make the repair — coupling a cracked lateral, clearing a clogged nozzle, freeing a stuck valve diaphragm, adjusting a rotor arc, or splicing a wire with a waterproof connector — then re-run the zone and confirm the repair holds.

Safety During Diagnosis and Repair

• PPE: Wear gloves, safety glasses, and sturdy closed-toe boots whenever you are digging or handling pipe fittings. Irrigation water is not potable; keep it out of your eyes and mouth.
• Electrical work: Before opening any controller cabinet or cutting any wire, confirm the controller is powered off. Follow lockout/tagout (LOTO) procedures: turn off and lock or tag the power source, then verify with your meter that power is absent before proceeding.
• Trenching: Never excavate around a lateral without checking for other buried utilities. Follow your program's dig-safe protocol. Keep bystanders clear of open trenches.
• Hand tools: Keep shovels and pipe cutters away from bystanders. Lay tools flat when not in use.

Catch-Can Audit Procedure

A catch-can audit tells you how evenly a zone distributes water — not just whether heads are running, but whether every part of the zone is getting its fair share.

1. Place cans in a uniform grid across the active spray zone — a minimum of 16 cans gives a reliable sample. Space them evenly, including areas between heads where low coverage is common.

2. Run the zone for a measured time (typically 15–30 minutes). Use a stopwatch for accuracy.

3. Collect every can immediately after the zone shuts off. Measure the water depth in each can using a ruler or graduated cylinder, recording to the nearest millimeter or tenth of an inch.

4. Calculate the overall average: add all depths and divide by the number of cans.

5. Calculate the lowest-quarter average: sort all readings from lowest to highest, select the bottom quarter of readings, and average those values.

6. Calculate Distribution Uniformity (DU):

> DU (%) = (Lowest-quarter average ÷ Overall average) × 100

A DU of 70% or above is generally considered acceptable for turfgrass irrigation. Drip and micro-irrigation systems can achieve 80–90%.

Interpreting DU and Writing Your Audit Report

A low DU means some areas receive far less water than others. The landscape manager must either over-irrigate the whole zone (wasting water on well-covered areas) or accept drought stress in low-coverage spots.

Your audit report should:

• State the DU result and compare it to the 70% benchmark.
• Map or describe where low-coverage cans were located.
• Propose specific corrective actions: replacing worn nozzles with matched-precipitation-rate nozzles, repositioning heads to eliminate dry gaps, adjusting pressure to the nozzle manufacturer's operating range, or adding a head to fill a coverage gap.
• Estimate water savings if DU improves. If the manager currently runs a zone 20 minutes to satisfy the driest corner, raising DU means that corner is covered at a shorter run time, reducing total applied water.

Connection to Your Credentials

The NALP Landscape Industry Certified exam tests practical irrigation knowledge including system diagnosis and water management. Demonstrating DU auditing shows the kind of measurable, professional work NALP evaluates. The State Pesticide Applicator license is not directly tested by this lesson, but responsible water management — avoiding runoff that can carry pesticide residues off-site — is part of the environmental stewardship required of licensed applicators.