How to Clean Glyphosate From a Sprayer

Cleaning glyphosate from a sprayer comes down to a thorough triple rinse with clean water, followed by targeted attention to filters, screens, and dead spots where residue hides. Glyphosate is water-soluble, which makes it easier to flush than many other herbicides, but “easier” does not mean a quick swirl and dump will do the job. The stakes are real: leftover glyphosate carried into your next application can kill or injure crops that were never meant to be sprayed, and the residue levels needed to cause damage are far lower than most people expect.

Why a Simple Rinse Is Not Enough

Glyphosate is a non-selective herbicide, meaning it damages or kills virtually any green plant it contacts. Even trace amounts left in your tank, hoses, boom, or nozzle bodies can injure sensitive crops on the next pass. The threshold for visible crop damage from glyphosate contamination can be remarkably low, sometimes in the parts-per-million range depending on the crop. A single pass over young soybeans or tomatoes with a “clean” sprayer that still holds a tiny fraction of a previous glyphosate load can cause stunted growth, yellowing, or outright death of the plants.

The problem is compounded by the sprayer’s design. A typical boom sprayer is not a simple bucket you can tip out. It has dozens of feet of plumbing, multiple filters, check valves, dead-end sections at the boom tips, and sometimes an induction bowl or chemical eductor. Every one of those components can trap a small volume of spray solution that does not drain when you empty the tank. Those trapped pockets are where contamination lingers between jobs.

The Triple-Rinse Method

The standard approach across the agricultural industry is a triple rinse, sometimes called a triple cleanout. The concept is straightforward: fill the tank with a volume of clean water, circulate it through the entire system including the boom and nozzles, drain it, and repeat two more times. Research on sprayer cleanout confirms this works. A study of 25 commercial agricultural sprayers found that a triple rinse with water achieved a cleanout efficacy above 99.99%, with concentrations in the fourth rinse dropping below detectable thresholds for crop injury, provided each rinse used at least 10% of the tank’s total volume.¹

Here is how to do it properly:

Drain the tank completely. Spray out remaining product in the field according to the label, then drain whatever is left from the sump. Open the drain valve and let gravity do its work. Some sprayers have a sump rinse nozzle built in; use it if you have one.
First rinse. Add clean water equal to at least one-tenth of your tank capacity. If you run a 1,000-gallon sprayer, that means at least 100 gallons per rinse. Run the pump to circulate water through all lines, boom sections, and nozzles for several minutes. Spray the rinse water out through the nozzles in the field or into an approved collection area. Remove and hand-rinse all nozzle screens and in-line strainers during this first rinse.
Second rinse. Repeat the fill-circulate-spray cycle. This is where most of the remaining residue comes out.
Third rinse. One more cycle. By the end, the concentration of glyphosate left in the system is a tiny fraction of what you started with.

The 10%-of-tank-volume rule for each rinse is a minimum, not a target. More water is better. If you have access to plenty of clean water, using 15 or 20% per rinse further reduces the residual concentration. The key is not to skimp on volume and not to skip the third rinse just because the water coming out of the nozzles looks clear. Glyphosate is colorless in diluted solution; you cannot judge contamination by appearance.

Cleaning Agents and When You Need Them

For glyphosate alone, plain water works well because glyphosate’s potassium or isopropylamine salt forms are highly water-soluble. This is one of the few situations where water by itself is genuinely effective for sprayer cleanout. Many operators still add a tank cleaner, and that is not a bad idea as extra insurance, but it is less critical here than it would be for herbicides that bind more stubbornly to plastic and rubber surfaces.

Where cleaning agents become more important is when glyphosate was tank-mixed with other products. Many field operations apply glyphosate in combination with residual herbicides, surfactants, or fertilizer solutions. Those tank-mix partners can be harder to remove than the glyphosate itself. Some herbicides, particularly sulfonylureas and synthetic auxins like dicamba and 2,4-D, bind to the interior surfaces of polyethylene tanks and rubber hoses. If your glyphosate application included any of those products, the cleanout protocol changes. You will likely need a commercial tank cleaner or a household ammonia solution (typically around 1% ammonia by volume) in addition to your water rinses. Always check the label of any tank-mix partner for specific cleanout instructions, because the most contamination-sensitive product in the mix dictates the cleanout procedure.

The Spots People Miss

Even a careful triple rinse can leave residue behind if you forget about the components that do not get flushed by simply running water through the main plumbing loop. These are the problem areas that cause most real-world cross-contamination incidents:

End caps and boom dead ends. The very tips of boom sections often have short lengths of hose or pipe beyond the last nozzle body. Fluid sits in these dead ends and does not circulate during a normal rinse cycle. Some operators crack open the end caps to let rinse water drain from these sections, or they install flush valves at the boom tips for exactly this purpose.
Nozzle screens and strainers. The mesh screens inside nozzle bodies and the in-line strainers catch debris, including dried herbicide residue. Pull them out and hand-rinse them in clean water during at least the first rinse cycle. A clogged screen can hold enough concentrated residue to contaminate dozens of gallons of fresh spray solution.
Induction bowls and chemical eductors. If your sprayer has a side-mounted chemical inductor or an induction hopper for adding product, that component has its own plumbing loop that may not be fully flushed during a standard boom rinse. Run rinse water through the inductor separately.
Pump housings and low points. Centrifugal and diaphragm pumps both have internal chambers that can trap small volumes of solution. Roller pumps are especially prone to trapping residue. Running the pump during each rinse cycle helps, but physically draining the pump housing between seasons or between very different product types is worth the effort.
Suction strainers. The strainer on the suction side of the pump sits at the lowest point of the tank and collects concentrated residue. Remove it and hand-clean it.

Operators who install dedicated flush lines or rinse nozzles inside the tank can address many of these trouble spots more easily, because those systems force water across internal surfaces the main pump does not reach. If you are buying a new sprayer or upgrading an older one, internal tank rinse nozzles are one of the most cost-effective contamination-prevention upgrades available.

Protecting Yourself During Cleanout

Sprayer cleaning is one of the higher-exposure tasks in pesticide handling because you are working in close contact with contaminated surfaces, residual spray solution, and splashing rinse water. Research on operator exposure during vineyard spraying found that the cleaning phase produced meaningful dermal exposure levels. Wearing a water-repellent coverall reduced body exposure by roughly 95%, and adding a certified protective gown during mixing, loading, and cleaning pushed that protection above 98%.²

At a minimum, wear chemical-resistant gloves, eye protection, and clothing that covers your arms and legs when performing a sprayer cleanout. If you are hand-rinsing screens and nozzle bodies, you are handling parts coated with concentrated residue, not the diluted field-rate solution. Gloves are not optional for that step. Avoid spraying rinse water toward yourself when flushing boom nozzles, and stand upwind if possible. Follow the personal protective equipment requirements on the glyphosate product label, and keep in mind that any tank-mix partners may require additional protection.

Disposing of Rinsate Responsibly

The rinse water you flush from a sprayer still contains herbicide, especially the first rinse. You have several options for disposal, and the right choice depends on your setup and local regulations.

The simplest approach is to spray the rinsate over the field you just treated, at a rate consistent with the product label. Since you already applied glyphosate there, the small additional amount from the rinse water is unlikely to cause any harm and stays on the target area. This is the most common field practice and is generally acceptable under pesticide regulations in most jurisdictions.

If spraying in the field is not practical, a dedicated rinsate pad with collection is an option for larger operations. Some farms use biological treatment systems, sometimes called biobeds, to handle pesticide-contaminated washwater. These systems use a mixture of soil, straw, and organic matter to promote microbial breakdown of pesticides. Research has shown that biobeds can degrade more than 99% of glyphosate within six months, with a half-life of about 33 days under tropical conditions.³ When biobeds are designed to retain and degrade pesticides from sprayer washings, they need to be lined to prevent any leaching into groundwater.⁴

What you should never do is dump concentrated rinsate into a storm drain, a ditch, or any waterway. Glyphosate is toxic to aquatic organisms at concentrations far higher than typical environmental levels, but concentrated sprayer washings are not typical environmental levels. Even diluted rinsate in a drainage ditch can reach surface water. Your state or national environmental agency likely has specific guidance on rinsate disposal; follow it.

Switching Between Herbicides and the Cross-Contamination Risk

The most common reason people worry about sprayer cleanout is not that they are putting the sprayer away for winter. It is that they need to switch products, often from a non-selective herbicide like glyphosate to a selective one, or from one selective herbicide to another. This is where the consequences of poor cleanout become visible fast.

Glyphosate residue carried into a broadleaf herbicide application on corn, for instance, will injure the corn. Residue of a growth-regulator herbicide like dicamba carried into a glyphosate application on non-tolerant soybeans can cause severe damage. The triple-rinse study referenced earlier was motivated precisely by this concern: even after sprayers achieved 99.99% cleanout, the researchers tested whether the remaining trace concentrations were low enough to avoid soybean injury from dicamba residues.¹ That framing tells you something important about the real-world risk: even a 99.99% cleanout leaves behind a tiny fraction of the original product, and for certain crop-herbicide combinations, even that tiny fraction can be a problem.

When you are switching from glyphosate to another product, the good news is that glyphosate flushes out of a sprayer more readily than many alternatives. When you are switching to glyphosate from something else, the concern flips: it is the previous product you need to worry about removing, not the glyphosate you are about to add. Either way, the cleanout procedure should be based on whichever product is hardest to remove and most damaging if traces remain.

Seasonal Storage and Deep Cleans

At the end of the spraying season, a standard triple rinse is the minimum before parking the sprayer. But long-term storage introduces additional concerns. Residual moisture left in hoses and pump housings can freeze and crack components. Dried residue left on internal surfaces over months can bond more tightly and become harder to remove in the spring. A more thorough end-of-season cleanout includes running an antifreeze solution (usually RV-type propylene glycol antifreeze, not automotive ethylene glycol, which is toxic) through the entire system after your final water rinse.

Before the first use the following spring, run a clean-water rinse through the system again. Any residue that dried on interior surfaces over the winter can dissolve back into your first tank load of the new season. That pre-season flush is cheap insurance against an early-season crop injury that is difficult to diagnose and impossible to undo.

Sprayer Materials and Glyphosate Compatibility

One practical advantage of cleaning glyphosate compared with many other pesticides is that it does not bind aggressively to common sprayer materials. Polyethylene tanks, EPDM rubber hoses, and stainless steel fittings all release glyphosate residue fairly readily when flushed with water. Some older sprayers with natural rubber gaskets or certain types of PVC tubing may absorb more product, but for equipment manufactured in the last couple of decades, material compatibility is rarely the bottleneck in a glyphosate cleanout.

This is not the case with all herbicides. Certain products, especially those in the sulfonylurea family, can penetrate and persist in polyethylene tank walls and rubber hoses to the point where no amount of rinsing fully removes them. Some operators who frequently switch between very different product types maintain separate sprayers for separate product families to eliminate cross-contamination risk entirely. If your operation applies both glyphosate and a crop-selective herbicide on a regular basis, and the sensitive crop is high-value, dedicated sprayers may save you more in avoided crop damage than they cost in extra equipment.

Common Mistakes That Lead to Crop Injury

Most cross-contamination incidents trace back to a handful of recurring errors rather than a fundamentally flawed cleaning process. Knowing what goes wrong for other operators can save you a costly lesson.

Skipping the third rinse. Two rinses feel like enough because the water looks clean. It is not. The concentration drop between the second and third rinses is meaningful, especially for products with very low injury thresholds.
Using too little water per rinse. A quick splash in the bottom of a 1,000-gallon tank does not create enough volume or turbulence to flush residue from the lines. Each rinse needs at least 10% of tank volume, and more is better.¹
Forgetting the filters. The suction strainer and nozzle screens accumulate the most concentrated residue in the system. If they are not removed and hand-cleaned, they can re-contaminate an otherwise clean sprayer the moment you start pumping your next product.
Not running rinse water through the boom. Filling the tank, sloshing water around, and draining it from the sump cleans the tank itself but leaves the entire boom, hose run, and nozzle assembly full of old product. The rinse water must be pumped through the boom and sprayed out the nozzles.
Letting rinsate sit overnight. Starting a cleanout and then leaving partially rinsed solution in the tank overnight lets residue dry onto surfaces and become harder to remove the next day. If you start cleaning, finish cleaning.

None of these mistakes are exotic. They are all shortcuts that seem reasonable in the moment, especially at the end of a long spray day. Building the triple-rinse procedure into your routine so it happens automatically, rather than relying on willpower at 8 p.m. when you are tired, is the single most effective way to prevent contamination problems.