6.7 Sprayer Maintenance, Tank Cleanout & Storage

6.7 Sprayer Maintenance, Tank Cleanout & Storage

Core Concept: A calibrated sprayer stays calibrated only if it is maintained. Worn tips over-apply, plugged screens starve individual nozzles, a failing pump drops pressure mid-pass, and - the most expensive failure of all - herbicide residue left in the tank kills the next customer's crop. In Arkansas, tank cleanout is not just good practice for Class E and Class F work: the rule sets a no detectable concentration standard and tells you where to install the sampling valve.

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Why Carryover Matters More Than It Looks

A sprayer tank, boom, and hoses hold residue in places rinse water does not reach - the pump body, the agitation line, hose crimps, the ends of the boom past the last nozzle, the strainer basket, and any dead leg of plumbing. Some chemistries are potent at parts per billion:

• Sulfonylurea and ALS-inhibiting herbicides injure sensitive crops at concentrations far below what plain water removes; residues adsorb to the plastic of poly tanks and hoses.
• Auxin herbicides (2,4-D, dicamba) are the classic Arkansas carryover problem - a trace of the previous load in a tank that then sprays cotton or tomatoes produces exactly the epinasty and cupping that generates a Department complaint.
• Some fungicides and insecticides are less aggressive but still capable of phytotoxicity on sensitive ornamentals.

The lesson: read the Storage and Disposal and cleanout sections of the label of the product you are removing, and the label of the product you are about to apply.

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Correct Cleanout Sequence

1. Empty the tank completely, applying the remaining spray mix to a labelled site at or below the labelled rate.
2. First rinse. Fill with 10 percent of tank capacity in clean water, circulate through the agitation system, then out through the boom and every nozzle, including the boom ends. Drain.
3. Cleaning solution. Fill to a labelled volume with water plus the cleaner specified on the label - typically household ammonia at the labelled concentration for sulfonylureas, or a commercial tank cleaner. Circulate thoroughly.
4. Dwell. Let the cleaning solution stand in the tank and lines for the time the label specifies - often 15 minutes to several hours, and for some products overnight. Circulate again before draining.
5. Drain, then remove and clean components separately: nozzle tips, strainers, screens, and the tank basket. Residue hides in screen mesh.
6. Two more clean-water rinses, again circulating through the boom and out all nozzles.
7. Dispose of every rinse into a labelled application, never to the ground or a drain.

[!WARNING] Exam Trap: Ammonia Does Not Neutralize the Herbicide Household ammonia is specified for sulfonylurea cleanout because it raises pH and helps lift residue off tank surfaces into solution, so it can be rinsed out. It does not chemically destroy the active ingredient. That is why the ammonia rinsate is still a pesticide-containing liquid that must be applied to a labelled site, and why the dwell and the subsequent rinses are not optional.

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The Arkansas Class E and Class F Standard

2 CAR Sec. 70-110(c)(3)(I)(viii) makes decontamination an enforceable performance standard rather than a procedure. Equipment used to apply Class E or Class F products may not be used for other products unless:

• The vehicle is thoroughly decontaminated;
• The tank is thoroughly rinsed and the rinsate disposed of in accordance with the label, or if the label is silent, collected and disposed of under applicable state and federal law; and
• The entire spray or application system is replaced or decontaminated using the best available technology such that a sample taken from the successive pesticide tank load would contain no detectable concentration of the previous product. Where research has established a no-effect concentration that is not itself a violation of law, that concentration is acceptable.

And the rule prescribes the hardware for verifying it:

• A leak-free valve painted hunter orange from which a sample can be taken;
• On aircraft, the sample valve is at the low point in the spray system;
• On ground equipment, the sample valve is in the pressure by-pass line.

Failing to decontaminate before applying a Class A through D product inside a designated Class E or Class F buffer zone is expressly treated as a buffer zone violation - which carries the added civil penalty of $1,000 on top of the matrix amount, capped at $2,000 total for a single violation.

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Routine Maintenance

Nozzle wear is silent and progressive. Abrasive formulations such as wettable powders erode orifices, and a worn tip delivers more volume in a coarser, less uniform pattern. Compare catch volumes against a new tip of the same size at the same pressure; the 10 percent rule is the standard replacement trigger.

Materials matter. Nozzle body and tip material determine wear life: polymer is inexpensive and chemically resistant, stainless steel is durable, hardened stainless and ceramic last longest with abrasive materials. Brass wears fastest and is a poor choice for wettable powders.

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Winter Storage

1. Clean the sprayer completely using the sequence above - never store a tank with product in it.
2. Drain all water from tank, pump, boom, hoses, filters and the flow meter. Water left in a diaphragm pump will freeze and crack the housing.
3. Circulate antifreeze compatible with the system through the pump and lines, or use a proprietary winterizing product.
4. Remove nozzle tips, screens and strainers, clean them, dry them, and store them indoors in labelled containers.
5. Relieve pressure in the system and, where the manual advises, back off regulators so springs and diaphragms do not take a permanent set.
6. Store out of sunlight. UV degrades poly tanks and hoses.
7. Grease fittings, and store with the tank lid loosely on to allow ventilation while keeping debris out.