Irrigation Startup and Audit

Purpose

Bring a winterized system back into service without breaking it, then measure what each zone actually applies. A startup that only turns the water on hides every winter failure until something else finds it: a cracked lateral shows up as a soft spot in June, a snapped nozzle as a water bill the customer opens in July, and a zone with poor uniformity as a dead patch the shop gets blamed for after telling the customer to water less.

The measurement half is what makes the visit worth billing. A controller run time is a guess until somebody knows the zone's precipitation rate and how evenly it lands, and until then every watering conversation with that customer is opinion against opinion.

Scope

Covers spring recommissioning and the hydraulic audit of an existing residential or light commercial system: pressurization, mainline hold test, zone walk and head repair, operating pressure at the head, and a catch-can distribution uniformity and precipitation rate measurement per zone.

Does not cover the backflow assembly test or controller programming, which are the LawnCare irrigation controller and backflow service SOP. Does not cover fall blow-out, which is the winterization and end-of-season shutdown SOP. Does not cover design changes, new zone construction, or the California MWELO compliance audit, which has its own SOP and its own report form.

Roles and handoffs

The handoff that fails is the measured number. A tech who repairs a zone and never passes the new precipitation rate forward leaves the controller running last year's schedule on this year's hydraulics.

Procedure

Step 1 - Confirm the system is put back together before adding water

Walk the point of connection and confirm the backflow assembly is reinstalled, test cocks closed, drains closed, and the controller powered. Acceptance: assembly present and oriented per its arrow, every test cock and drain closed by hand, controller display lit or the transformer confirmed energized. Wrong looks like a system pressurized with a winter drain still open, which sprays under the meter box for as long as it takes somebody to notice. If wiring must be opened at the controller or transformer, kill that branch circuit at the panel and prove the terminals dead with a meter, live-dead-live per NFPA 70E-2021, 120.5; the controlling practice for that work is 29 CFR 1910.333(b)(2), not the general lockout standard.

Step 2 - Pressurize slowly and let the mainline fill

Crack the isolation valve about a quarter turn and let the mainline fill until flow noise stops, then open it fully. Acceptance: static pressure steady on a gauge at a hose bib or test cock, no hammer, no sustained hiss anywhere on the line. Wrong looks like opening the valve wide, which slams a column of water into a system full of air and can split a poly fitting, blow a nozzle off a riser, or lift a check in an assembly reinstalled ten minutes earlier. If you hear hammer, close the valve and start again slower. Stand clear of the assembly's relief port while filling, because an RP assembly can discharge a hard stream on the initial pressure swing.

Step 3 - Hold the mainline with every zone off

With all zones closed, watch the pressure gauge and the water meter's low-flow indicator for a full 10 minutes. Acceptance: gauge steady and the leak indicator motionless for the whole 10 minutes. Wrong looks like a slowly creeping leak dial with nothing running, which means a mainline leak or a valve not seating, and both waste water continuously rather than only during a cycle. If the indicator moves, do not leave the system pressurized: close the isolation valve, isolate by section to find it, and if the leak cannot be located that visit, leave the system off, red-tag the controller and tell the customer why in person.

Step 4 - Walk every zone and mark what is wrong before repairing anything

Run each zone from the controller and walk it head by head, marking faults with flags rather than stopping to repair. Acceptance: every head accounted for against the zone map, each riser retracting fully, each rotor turning through its set arc, no geyser, no head buried below turf level. Wrong looks like repairing the first broken head and losing track of the other four, which is how a zone gets signed off with a fault still in it. If a head is missing entirely and the lateral is open, shut that zone off at the controller before continuing, because an open lateral drops pressure across every other head on the zone and makes the rest of the walk meaningless.

Step 5 - Read operating pressure at the head, not at the meter

Put a pressure gauge on a nozzle at the far end of the zone with the zone running. Acceptance: reading inside the band the nozzle chart gives for that model, commonly around 30 psi at the nozzle for fixed sprays and roughly 45 to 65 psi for gear-drive rotors, checked against the chart for the head actually in the ground. Wrong looks like misting or fog at the head, which is over-pressure atomizing the spray into droplets the wind removes, or a weak stream with a dry ring under the head, which is under-pressure. Over-pressure gets pressure-regulating stems or regulated bodies, not a throttled valve, since throttling a valve to fix pressure at one head starves the rest of the zone.

Step 6 - Run a catch-can test on each turf zone

Set catch cans of one type on a uniform grid across the zone, including under and between heads, run the zone for a timed period long enough to give a measurable depth, and record every can. Acceptance: at least 12 cans on a residential zone, run time 10 to 20 minutes for rotors, and wind under about 5 mph during the test, since a breezy test measures the weather rather than the system. Wrong looks like cans placed only in the open middle of the lawn, which flatters uniformity by skipping the corners the system struggles to reach. If wind picks up mid-test, discard the run and repeat rather than recording a number that will be used to set a schedule all season.

Step 7 - Compute uniformity and precipitation rate, then decide before scheduling

Average all cans for the mean, average the lowest quarter of cans for the low-quarter mean, and divide: low-quarter distribution uniformity is the low quarter mean over the overall mean. Precipitation rate in inches per hour is the mean catch depth multiplied by 60 divided by the run minutes. Acceptance: uniformity at or above 0.70 accepted as a good result for an existing rotor zone. Wrong looks like a uniformity under about 0.50, and the stop rule is that the zone is repaired before it is scheduled, not scheduled longer to compensate. These thresholds come from the Irrigation Association's landscape auditor practice, a consensus method rather than a code, and they bind you only where a water agency or a customer specification adopts them.

Step 8 - Write the numbers and hand them to the programmer

Record the per-zone numbers and every deferred repair before leaving. Acceptance: uniformity, precipitation rate, operating pressure and head count recorded per zone, and each deferred repair listed with the zone and the reason. Wrong looks like a startup invoice that says "system checked, all zones operational", which tells the next tech nothing and lets the same fault be rediscovered next spring. If a zone was not tested, write not tested and why, rather than leaving the field blank where it will be read as a pass.

The record this produces

One startup and audit record per property: date, tech, static pressure, mainline hold result with its duration, and then per zone the head type and count, operating pressure at the far head, repairs made, catch-can run time, number of cans, mean catch depth, low-quarter mean, low-quarter uniformity, and computed precipitation rate in inches per hour.

The per-zone precipitation rate and uniformity go straight to whoever programs the controller, and they are the only legitimate basis for a run time. They also land on the property card so next spring's audit compares against a real number instead of a memory, which is how a slowly degrading zone gets caught before it browns out. Deferred repairs go to the office as scheduled work with the zone named. The record is also what answers a customer who says the lawn is watered too much or too little: it states what the system actually applies, measured on a date, which is a different and much stronger claim than what the controller is set to run.

One pass through this procedure

Property: six zones, zone 3 is six gear-drive rotors on a 40 by 60 ft rear lawn. Steps 1 through 5 pass: mainline holds for 10 minutes with the leak indicator still, two broken nozzles on zone 2 replaced, and zone 3 reads 48 psi at the far head, inside the chart band for that rotor.

Step 6 lays 12 cans on a grid and runs zone 3 for 20 minutes. Catches, in inches: 0.40, 0.39, 0.38, 0.36, 0.34, 0.32, 0.31, 0.29, 0.27, 0.15, 0.14, 0.13. Total 3.48, mean 0.29 in. Precipitation rate is 0.29 times 60 divided by 20, or 0.87 in per hour.

Step 7 fails. The lowest quarter is three cans averaging 0.14 in, so uniformity is 0.14 over 0.29, which is 0.48. That is under the 0.50 stop threshold, so the zone does not get scheduled. Working the schedule instead would have been the tempting move and the arithmetic shows why it is wrong: to put 0.50 in on the driest quarter at that uniformity the zone would need 0.50 divided by 0.87, or 34.5 minutes, divided again by 0.48, which is 71.8 minutes, and everything under the good heads gets soaked to reach the bad ones.

The cause is found on the fault list from step 4. Two of the six rotors carry nozzles from a different series than the other four, so the half-circle heads at the fence deliver near the same flow as the full-circle heads while covering half the area. Matched nozzles go in, and the zone is re-tested the same visit: mean 0.31 in over 20 minutes, so a precipitation rate of 0.93 in per hour, low-quarter mean 0.22 in, uniformity 0.71. Now 0.50 in on the driest quarter takes 32.3 minutes divided by 0.71, or 45.4 minutes, which is 37 percent less run time than the pre-repair figure for the same depth.

Step 8 records both runs, the pre-repair 0.48 and the post-repair 0.71, so the record shows what the repair bought rather than just the final number. The 0.93 in per hour goes to the controller SOP, where cycle-and-soak splits that 45 minutes against the soil's intake rate.

References

• NFPA 70E-2021, 120.5, for the live-dead-live proving sequence in step 1, and 29 CFR 1910.333(b)(2), which is the controlling OSHA practice for the electrical work at a controller or transformer
• Irrigation Association landscape irrigation auditor practice, the source of the low-quarter distribution uniformity method and the scheduling multiplier used in step 7; a consensus method that binds you only where a water agency or customer specification adopts it
• The nozzle performance chart published by the manufacturer of the head in the ground, which is the source of the pressure band in step 5
• See related: the LawnCare irrigation controller and backflow service SOP, which owns the programming and the assembly test, and the winterization and end-of-season shutdown SOP, which owns the blow-out this startup reverses