Irrigation Head and Nozzle Replacement Visit

Purpose

Replace a broken or wrong head so the zone comes back hydraulically the same as its neighbors, instead of quietly worse.

A head swap looks like a parts job and is not. Every head on a zone shares one lateral, so what goes back changes what the others get. Put a full-circle nozzle in a half-circle position and that corner takes twice the depth of the rest, which the customer reports weeks later as a soggy patch. Put a plain body where a checked one was and the lateral drains out the low head every cycle, scouring turf. Neither shows up on the day, which is why the acceptance conditions here are numbers.

Scope

Covers the corrective visit to replace a damaged, buried, misted or mismatched spray or rotor head and its nozzle on an existing residential or light commercial zone, including the riser under it and a short lateral repair at that fitting.

Does not cover spring commissioning, the mainline hold test or the catch-can uniformity audit, which the irrigation startup and audit SOP owns, nor controller programming, solenoids, wiring or backflow testing, which the controller and backflow service SOP owns along with any work inside a powered controller or transformer. Zone redesign and added heads are quoted work.

Roles and handoffs

Procedure

Step 1 - Kill the water and prove the lateral is dead

Set the controller to OFF and close the zone isolation valve where one exists. Acceptance: the display reading OFF, no zone advancing on its own while you work, and no flow or residual pressure when the damaged head's nozzle is cracked open. Wrong is a rain delay, which times out and starts the zone with the lateral open; stop rule, a system with no isolation valve is shut at the point of connection, written on the ticket because step 8 has to put it back. Hazard: a spray body still under pressure ejects its nozzle at face height, so make the residual-pressure check from the side with eye protection on, never leaning over the head.

Step 2 - Read what is in the ground before ordering what goes back

Record off the body, the nozzle and that model's spec sheet: manufacturer and series, pop-up height, inlet thread size, whether the body regulates pressure and at what set pressure, whether it carries a check valve and its published rating in feet of elevation head, and the nozzle's marked arc and radius. Acceptance: all of those written down, read off the parts rather than recalled. Wrong is ordering by pop-up height alone, which is how a checked, regulated body gets replaced by a plain one; stop rule, unreadable markings mean pulling a matching head elsewhere on the zone and reading that. Hazard: none, the lateral drained at step 1.

Step 3 - Hand-dig to the fitting, not to the head

Cut and lift the sod plug whole, set it grass up, and hand-dig to the inlet fitting and the riser under the body. Acceptance: fitting and riser exposed, plug intact, spoil on a tarp rather than in the turf. Wrong is driving a shovel blade down beside the head, which cuts the lateral you came to save; stop rule, unmapped ground or any powered digging waits for a one-call ticket, with the notice period and hand-dig exemptions set by your state's law rather than a national rule. Hazard: yards carry low-voltage lighting cable and shallow gas services to grills and pool heaters. Cut lighting means stop and kill that circuit at its breaker or by pulling the transformer's plug, never by opening the powered transformer, which the scope excludes; a struck gas service means everybody walks upwind off the property, no engine started, no phone used at the trench, utility and 911 called from a distance.

Step 4 - Replace the reason it broke, not only the part that broke

Put the body back on something that articulates, a swing joint or flexible riser, not the rigid nipple that fed the strike straight into the lateral fitting. Acceptance: the assembly flexes by hand through its travel with the body plumb, and no cracked or weeping fitting left in the trench. Wrong is a new head threaded onto the old rigid nipple, which returns the same break on the next strike; stop rule, a cracked lateral or fitting becomes a pipe repair before any head goes back on. Hazard: solvent cement vapour is heavier than air and pools in the trench and valve box, so work upwind with your head out of the hole, never inside a box; its solvents are tetrahydrofuran, ketones and acetone, which break through nitrile in minutes, so the glove is the material the product's safety data sheet names, commonly butyl or a laminate film; it is flammable, so no running engine at the trench; eye contact is flushed per the SDS, then medical attention.

Step 5 - Flush the lateral before any nozzle goes in

Fit the body with no nozzle, or with the manufacturer's flush plug, and run the zone until the discharge runs clear. Acceptance: clear discharge held for 30 seconds at the replaced head, with this head flushed last on the zone so grit from the other repairs has somewhere to go. Wrong is fitting the nozzle first, which packs grit into it and its filter screen and gives a misted or dead head within a week; stop rule, discharge that never clears means an open break upstream, so shut the zone and trace it rather than nozzling up. Hazard: an open body throws grit and water at eye height, so stand to the side with eye protection, keep everyone out of the arc, and let one person own the valve so the zone cannot start with a hand on the head.

Step 6 - Pick the nozzle by precipitation rate, not by radius

Single-head precipitation rate in inches per hour is 96.3 times the nozzle's chart flow in gallons per minute divided by the area it wets in square feet, 96.3 being the unit conversion. That is the head's own sector with no overlap, not the zone rate the startup SOP's catch-can test measures, so the two are never compared. Acceptance: replacement from the same series as its neighbors, arc matching the position, computed single-head rate within 10 percent of theirs at the same chart pressure. Wrong is a full-circle nozzle in a half-circle position, the same flow over half the area, doubling depth there; stop rule, a series no longer stocked means the zone's nozzles change as a set on a work order, never one odd head. Hazard: none, a chart decision with the zone off.

Step 7 - Set the head to grade and set the arc

Set the body so its top sits flush with finished grade to about a quarter inch below, never proud, then set the arc. Acceptance: a straightedge across the head touching turf either side, the body plumb, and the pattern landing on turf rather than the walk, the window or the road. Wrong is a proud head, which the mower deck clips and which is why most replacements come back; stop rule, a body that cannot reach grade gets its riser cut to length rather than left high or buried under sod, since a buried head waters the soil around itself. Hazard: backfill in lifts and firm by hand rather than by boot on a fresh swing joint, and keep fingers clear of the riser when the zone is bumped to check the arc.

Step 8 - Put the water back, verify what you disturbed, restore the controller

Run the zone, then check both protective functions this repair touched. Acceptance: nozzle pressure at the far head inside the chart band for that nozzle, drainage stopping within 60 seconds of shutdown with no standing water at the zone's lowest head, the controller returned from OFF to its schedule and confirmed on the display, isolation valve reopened, box lid on, sod plug reset and watered. Wrong is a low head that weeps for minutes after every cycle, which is low-head drainage and says the check function you disturbed is gone; stop rule, pull the body and refit one whose published check rating exceeds the measured elevation difference between the highest and lowest head on that zone, then re-run this step. Hazard: this step puts pressure back with people around, so nobody stands over a head at start and the tech waits outside the pattern.

The record this produces

One repair line per head: zone and head number, cause, body series and pop-up height, regulation set pressure, check rating in feet, nozzle arc and radius, computed single-head rate, riser type fitted, flush time, pressure at the far head, drainage time after shutdown, date.

The cause column is what the office reads across a season: three strikes on one head is a mowing pattern or a proud head, and routes to the mowing standard rather than the parts order.

One pass through this procedure

Zone 4, eight fixed spray heads on a front lawn falling from the walk to the street corner. Two complaints: head 4-8 at the low corner sheared off at grade by a mower, and a soggy strip along the fence at head 4-7.

Steps 1 to 3 pass: controller to OFF, isolation valve closed, no residual pressure at 4-8, sod plugs lifted whole, both fittings hand-dug and exposed. Step 2 reads the neighboring bodies as 4 in pop-up, one series, regulated at 30 psi, check valve published at 14 ft of elevation head on that model's spec sheet. Step 4 puts both heads on swing joints; 4-8 had been on a rigid nipple, which is why a deck strike sheared it. Step 5 flushes 4-8 last, clear at 30 seconds.

Step 6 finds the fence problem. The chart for that series at 30 psi reads 3.7 gpm for the 12 ft full-circle nozzle and 1.85 gpm for the 12 ft half. A 12 ft full circle wets pi times 12 squared, or 452.4 sq ft, so 96.3 times 3.7 divided by 452.4 is 0.79 in per hour. The half wets 226.2 sq ft, and 96.3 times 1.85 divided by 226.2 is also 0.79, which is what matched precipitation means. Head 4-7 is a half-circle position carrying a full-circle nozzle: 96.3 times 3.7 divided by 226.2 is 1.58 in per hour, twice its neighbors. On the 20-minute cycle that corner takes 1.58 times 20 divided by 60, or 0.53 in, against 0.26 in elsewhere, a surplus of 0.27 in per cycle and 0.81 in across three cycles a week. A 12 ft half-circle nozzle goes in.

Step 8 fails. Pressure at the far head reads 30 psi at the regulated body, inside the chart band, but 4-8 weeps for over four minutes after shutdown and puddles. The stop rule applies: the body pulled from the van was a plain one. Elevation from head 4-1 at the walk down to 4-8 measures 5 ft, under the 14 ft published rating, so a checked body of the same series goes in and step 8 re-runs. Drainage stops in 20 seconds, inside the 60-second acceptance, no standing water. Controller returned from OFF to its schedule, valve reopened, lids on, plugs reset and watered.

When the site does not match. If the series is obsolete, the zone's nozzles change as a set rather than mixing families, quoted before anything is fitted; if the customer declines, the zone runs to its worst head and the ticket says so. If zone elevation exceeds every available check rating, the fix is a check valve in the lateral, not a bigger head, and that is a work order.

References

• The manufacturer's nozzle performance chart and body spec sheet for the head in the ground, the source of the chart flows, set pressure and check rating used here
• Your state's one-call law for the notice period and hand-dig exemptions in step 3, which varies by state rather than being set nationally
• The solvent cement maker's directions and SDS for the ventilation, glove and ignition controls in step 4
• Irrigation Association landscape auditor practice for the split between a single-head precipitation rate and the measured zone rate; binding where a water agency or customer specification adopts it
• See related: the LawnCare irrigation startup and audit SOP for the catch-can zone rate, the irrigation controller and backflow service SOP for programming and the assembly test, and the drainage and standing water complaint visit for a wet area with no head fault