6.5 Equipment Maintenance, Sprayer Cleanout, and Rinsate Management

Maintenance Is a Legal Duty, Not Just Good Practice

ATCP 29.50(5)(a) states that, with one exception, no person may use, furnish, lease, or sell pesticide application equipment that is clogged, unclean, leaking, or in disrepair, or that cannot be properly calibrated to apply pesticides at the rate specified on the pesticide label. The single exception in ATCP 29.50(5)(b) covers a sale in which the seller discloses the defective conditions to the buyer in writing before the sale.

Read that carefully, because the verbs are broad: use, furnish, lease, or sell. A contractor who lends a leaking backpack to a crew member has "furnished" it. No off-target movement needs to be proven; the condition of the equipment is itself the violation.

The Maintenance Routine

Before every job

• Walk the boom with the system pressurized with clean water and look for drips, streams, and pattern distortion.
• Check that the pressure gauge reads zero at rest and rises smoothly.
• Confirm screens and strainers are in place and clean — tank fill screen, line strainer, and nozzle screens.
• Verify agitation is working; a suspension that settles out delivers water at the start of the load and concentrate at the end.
• Confirm the spray pattern is uniform at operating pressure.

After every job

• Rinse before residue dries. Dried residue is dramatically harder to remove and is the origin of most contamination claims.
• Rinse the outside of the machine as well; the boom, tank exterior, and wheel wells carry residue into the shop and the road.
• Drain low points and the pump if freezing is possible.

Seasonally

• Measure nozzle output against a new tip of the same size at the same pressure. Replace the tip when output exceeds the new-tip output by more than about 10 percent. Worn orifices deliver more, not less, and they distort the pattern and shift the droplet spectrum finer, increasing drift.
• Check individual nozzles against the boom average during every calibration. A single nozzle more than about 10 percent off the average should be cleaned or replaced.
• Verify the pressure gauge against a known-good gauge; a gauge reading 10 psi low makes every calibration wrong.
• Inspect hoses for cracking, swelling, and soft spots, and replace any hose that has hardened.
• Service the pump — diaphragms, seals, and oil — per the manufacturer's schedule.
• Winterize by draining the system completely and circulating an appropriate antifreeze through pump, lines, boom, and nozzles.

Never clean a plugged nozzle by blowing through it with your mouth or by probing with a knife, wire, or nail. Blowing puts concentrate in your mouth. Metal probes permanently enlarge and distort the orifice, which is the same as installing a worn tip. Use a soft brush and water, or a dedicated nozzle-cleaning tool.

Tank Cleanout: Dilution in Stages

The key principle is that several small rinses remove far more residue than one large one. Ten gallons used as three separate rinses beats a single ten-gallon flush by a wide margin, because each rinse starts with a lower residue concentration in the rinse water.

The standard procedure

+-----------------------------------------------------------------------------+
|                    SPRAYER CLEANOUT SEQUENCE                                |
|                                                                             |
|  0. SPRAY OUT the remaining tank mix on a labeled site at labeled rates      |
|  1. RINSE #1  Fill 10% of tank capacity, agitate, circulate through the      |
|               boom AND every nozzle, spray out on a labeled site             |
|  2. DISASSEMBLE screens, strainers, nozzle bodies, and boom end caps;        |
|               clean them separately -- residue hides here                    |
|  3. RINSE #2  Add the labeled cleaning agent (ammonia solution or a          |
|               commercial tank cleaner), fill, agitate, CIRCULATE, and let    |
|               it stand for the time the cleaner's label specifies           |
|  4. Spray out the cleaning solution on a labeled site                        |
|  5. RINSE #3  Clean water; circulate and spray out                           |
|  6. Reinstall clean screens; leave the tank open to dry                      |
+-----------------------------------------------------------------------------+

Three details separate a real cleanout from a rinse:

1. Circulate through the boom and out every nozzle. Residue sitting in a boom section, an end cap, or a dead-leg plumbing run is the most common source of the next load's contamination. Sloshing water in the tank does nothing for the plumbing.
2. Disassemble the small parts. Screens, strainers, nozzle bodies, and boom end caps trap concentrated residue and sediment.
3. Use the cleaning agent the label names. Growth-regulator herbicides such as 2,4-D and dicamba, and sulfonylurea herbicides, injure sensitive crops at concentrations far below what water alone will remove. Household ammonia solution and commercial tank cleaners work by raising pH and solubilizing residues; both need contact time, not just a pass-through.

Safety rule with no exceptions: never mix ammonia with chlorine bleach. The combination releases chloramine gases that can cause severe respiratory injury. Choose one cleaner, flush completely between products, and follow the cleaner's own label.

When cleanout matters most

• Before switching to a sensitive crop. Tomatoes, grapes, cucurbits, tobacco, and most vegetables and ornamentals are injured by trace growth-regulator herbicide residues. Wisconsin's cranberry marshes, orchards, vineyards, and vegetable acreage make this a real and frequent risk.
• Before switching herbicide chemistry — a sulfonylurea residue can injure a following crop at parts-per-billion levels.
• Before storage, so residues do not dry in place and corrode components.
• After a suspension or dry-flowable product, which settles into every low point.
• Whenever a rig is shared between operations or rented out.

Document your cleanout. A dated cleanout record is often the only evidence available when a neighboring grower alleges herbicide injury weeks later.

Rinsate: One Legal Destination

Rinsate is the dilute pesticide solution produced by rinsing tanks, containers, and equipment. It is a pesticide, and Wisconsin treats it as one.

ATCP 29.47(1): no person may dispose of any pesticide or pesticide container, or hold any for disposal, in a manner inconsistent with label directions, that risks contaminating the waters of the state, or that creates a hazard to persons, property, or the environment.

The practical consequence is that the routine legal answer is a single one:

Apply rinsate to a site listed on the label, at or below labeled rates, as part of a legitimate application.

Everything else is a problem. Do not pour rinsate on the ground, into a ditch, into a storm drain, into a sanitary sewer, into a septic system, or onto a gravel driveway. Do not accumulate it in unlabeled drums indefinitely — holding pesticide for disposal in a hazardous manner is itself prohibited by ATCP 29.47(1).

Two practices make this easy:

• Mix only what you need. Calculate the exact tank load for the acreage remaining. Leftover mix is the single largest source of rinsate.
• Use a closed rinsate recovery system, where rinse water is captured in a dedicated, clearly labeled tank and used as the carrier water for the next load of the same product. This is the cleanest solution: the rinsate never becomes waste at all.

Where rinsate must be stored temporarily, hold it in a clearly labeled, closed container identifying the product and concentration, under cover, on a containment surface, and use it as carrier water at the next opportunity. ATCP 29.48(3) adds a hard limit that applies to spill material generally: no spilled pesticides or spilled materials containing pesticides may be stored below ground level.