Editor’s Note: Changes have been made to this article since its original publication in 2015.
When in-crop spraying is around the corner, sprayer tank clean out is an important topic to address on your farm. Many farms have done the same clean-out routine for years and not had any issues with contaminating residues in the tank resulting in crop damage. Although the old saying “If it ain’t broke, don’t fix it” definitely has some merit, in this case it is good to question whether your cleanout routine is adequate. When you consider the way chemicals have changed over the years, especially the higher reliance on oily surfactants in modern chemicals, it makes sense why we need to pay attention to spray tank cleanout.
The goal of cleaning the tank is to remove and dilute the previous chemical formulation as much as possible to prevent buildup and carryover of residues which can cause crop damage on non-target crops.
Safety First
Always wear safety gear before working around chemicals. Although it can be a hassle, we all know that it is no fun spilling chemical on your clothes and skin. What’s even worse is smelling it all day in the sprayer cab. I use a long waterproof coat, a plastic face shield to prevent back splash when spiking jugs, and of course rubber gloves (No judgment on me looking like a total dork please:).
Safety First – Are you looking at my headgear? Are you!?
1 – Get the Previous Product Out of the Tank ASAP
In my experiences spraying, I have always tried to get the previous product out of the tank as soon as possible. Spraying the extra product out of the tank is the safest and most environmentally responsible way to rid your tank of left over product. Dr. Tom Wolf of AgriMetrix Research and Training, states that spraying a crop twice is usually safe, as all herbicides must be registered to be sprayed at twice the rate in order to be registered by the Pest Management Regulatory Agency (PMRA). If one lets the product sit in the tank overnight before beginning the cleanout, there is more time for product to congeal and adhere to the tank and plumbing components.
Ball valve on main filters.
I open the valve ends on my filters to empty the buildup in the bottom of the filter canister. There is often chemical residue or green slime from dug-out water in here. Next I like to go along my booms and empty out all the chemical product within the boom plumbing. Our farm runs a Patriot 4420 sprayer, with valves on each boom section to empty out product. Usually I will go to the sprayer and tip the boom ends up so that gravity allows all of the product to drain out. Then I raise the centre rack, and tip end of booms down to force the product to drain out the other way. You would be amazed at how much product comes out by doing this both directions!
Valves on each nozzle.Tipping the boom ends up with the centre rack down.
While the tank is empty and no pump is running, I will remove all the filters on the sprayer, and grab the handy dandy toothbrush – this is the most valuable tool in filter cleanout! This brush is just small enough to get it in the centre of the filter and scrub all of the residue and gunk out of the filters. A pail filled with rinsing solution is an easy way to clean filters and nozzles.
Possibly the most important cleaning tool. Don’t put it back in the bathroom afterwards.
2 – Begin Rinsing Process
I used to always put about 1,000 gallons of water to our 1,200 gallon tank, thinking that a larger volume would clean all areas of the tank better, but I’ve since changed my thinking. Research has shown that two or three smaller rinses *aka triple rinsing) is more effective for rinsing the tank than one large volume rinse. I always crank the agitation up to high and allow the cleaning solution to agitate for as long as possible.
Nowadays I try to do three 400 gallon rinses.
1st Rinse
Cleaning product plus 400 gallons water
2nd Rinse
Cleaning product plus 400 gallons water
3rd Rinse
400 gallons of just water to rinse, and run through plumbing system to check nozzles and for leaks
Many labels Recommend leaving the rinsing solution in the tank and lines overnight. This will allow more chemical deposits to loosen up. If an operator is forced to speed up the tank cleaning process due to limited time, they must understand that there are risks involved in doing a less thorough tank cleaning.
Cleaning Products
Detergent or ammonia? Check the label. If the label doesn’t specify, you can consult this table from Winfield United.
Detergent Cleaner
Ammonia
Solution contains an adjuvant
Sulfonylureas (SU’s)
Solution contains a milky looking component (an Emulsion or EC)
Thiencarbazone – methyl
Glufonsinate
Flucarbazone
Imi’s (Group 2)
Dicamba
Simplicity
Detergent (e.g. All Clear)
This detergent cleaner is specifically designed to remove pesticide deposits and other debris, including oily substances from booms, filters, and nozzles. Use All Clear (or other detergent cleaner) if the solution is milky-looking (called an emulsion), which means it is oil-based.
Label rate is 0.25 L of All Clear/100 L of water.
If you are adding 400 gal of water, you will only need 3.78 L of cleaning product.
Decontamination rate is double this: 7.57 L of cleaning product. Use this rate if you have had residue issues, or to do a more thorough cleaning.
pH Increaser (aka Ammonia; e.g. Flush)
This is an ammonia based cleaning solution. This product is used to raise the pH to increase solubility of most Group 2 products (from FMC, Bayer, and Corteva but not BASF). Flush contains 7% ammonia. Use Flush (or other ammonia based cleaner) for most cleaning, but especially for Group 2 products listed above, such as Varro, and Velocity M3, Express, Refine, Muster, and Spectrum.
Label Rate is 0.50 L of Flush/100 L of water.
If you are adding 400 gal of water, you will need exactly 7.57 L of cleaning solution.
A pail and detergent are “must-haves” during sprayer cleanup.
Combo Products
Alternately, some solutions raise pH without ammonia. FS Rinseout is sodium hydroxide based, not ammonia based. It is a high alkaline solution that elevates and holds the pH combined with strong surfactants to help clean the tank. Another is CleanOut, which uses potassium hydroxide and disodium metasilicate, a detergent. In both cases they are both pH increases and detergents.
3 – Draining the Rinse Solution
After I have ensured all nozzles are working correctly, and there are no leaks in the system, I drain out all of the rinse water, fold in the booms, and get ready to fill the tank with chemical solution for spraying!
More Information
Learn where residue can hide. This video was filmed for the Environmental Farm Plan with the nice people at Clean Field Services in Drayton, Ontario. Hardly the height of our acting careers, but good messaging nonetheless.
When operators winterize their sprayers, they should remove all the tips and store them separately. Many store them in large pails with lids. Calibrating the sprayer just prior to winterizing will indicate if the nozzles should be stored, or replaced. Let’s assume each tip flow rate is within 5% of the average output and no more than 5% more than the manufacturer’s pressure tables. Yes, industry standard is 10%, but I always wonder how the spray quality suffers with that much wear. Nozzles are, comparatively, a cheap replacement and it’s not worth skimping. Learn more how to check nozzle flow rate, here.
Just like any other part of the sprayer that comes in contact with spray liquid, nozzles (and strainers) should be cleaned regularly. And, just like any other part of the plumbing, the best way to do that is to dilute any residues via a series of rinses. For a more rigorous cleaning, one of the intermediate rinses should include a detergent, and soaking during this step is an excellent practice.
The orifice of any nozzle is delicate, either machined or molded to exacting standards. Even small changes to the orifice shape results in distorted spray (e.g. spray comes out at undesirable angles), a change to the rate (typically more volume per minute) and a change in the spray quality (typically larger median droplet size). If foreign objects or residues remain in the tips, the subsequent spray job may be less accurate and even damage the tips.
In the case of air induction nozzles, which are essentially the standard on most boom sprayers, debris and weed seeds can plug the air-intake ports. When that happens, the nozzle will not function as intended. So, while the occasional soaking of nozzles does a great deal of good, they may also have to be scrubbed. Don’t use picks or reamers! There are nozzle cleaning tools out there, but they’re basically toothbrushes so save your old ones (and mark them clearly). Soft bristles are the way to go for removing stubborn residues and cleaning any tip orifices, but we found a nifty new way:
Occasionally we receive photos like the one below and we’re asked what we think. Well, just the same way we don’t recommend cleaning your sprayer overalls in the family clothes washer, we also don’t recommend the use of dishwashers for nozzles.
Not a great idea. Certainly not if you intend to ever use this dishwasher for anything else. And where does the rinsate go?
In an interesting experiment, Lucas Olenick of Wilger tried cleaning tips in a heated ultrasonic cleaner. We haven’t tested this and we don’t know what heat and vibration might do to poly and ceramic components, but surely it’s no more aggressive than hot, soapy water and a bristle brush. Lucas tried several durations with and without detergent and arrived at this recipe:
“For tough, non-water-soluble pesticides, around 8+ hours in a heated ultra-sonic cleaner with (Dawn) dish soap to come out like brand new. Other solvents may speed this up, but I’d generally suggest against heating solvents at any concentration. For water-soluble pesticides, expect to be within the 3-6+ hours for the first time to be confident enough in not having to flow-test each of the nozzles. With any pesticides, ensure proper care in handling contaminated nozzles and rinsate after cleaning nozzles.”
The mad genius of Lucas Olenick (@WilgerParts) who used dish detergent and a heated sonic cleaner to unplug tips. Be sure to dispose of rinsate safely. Photo credit: Lucas Olenick.
Don’t have a heated sonic cleaner? No problem. Here’s a step by step:
Wearing gloves, remove all nozzles, strainers, rubber gaskets and tips from the sprayer.
Put them in a large plastic pail and cover them in warm water. Leave them to soak.
Drain the pail, but be aware that the rinsate will have pesticide residue.
Fill a second pail with a solution of the same commercial detergent used to clean the sprayer.
With a toothbrush, scrub the caps, gaskets, strainers and nozzles to remove any residue. Some nozzles can be pulled apart to expose the mixing chamber and facilitate cleaning.
Once scrubbed, leave all the parts to soak in the detergent solution.
Drain the solution, which will contain trace amounts of pesticide, rinse the parts with water and reassemble the nozzles.
While you’re at it, drop those filters and scrub them alongside the tips. This may seem extreme, but of all the technology on a sprayer, the nozzle has the biggest impact on the effectiveness and efficiency of the spray job. Take the opportunity over the winter months to clean and inspect the tips for damage so the sprayer is ready for calibration in the spring.
Soak, scrub, rinse and store nozzles and nozzle strainers. You may replace them once the sprayer is clean, but I prefer to store then separately. Photo credit: Jason Boersma (@RVFBoys), Ridge Valley Farms, Ontario.
Thanks to Jason Boersma (@RVFBoys), Ridge Valley Farms, Ontario, who sparked this article with his tweet: “Great job for a cold winter day, soak & clean all your tips to be ready for spring also saves on down time!”
Cleaning, flushing, triple-rinsing… whatever you call it, sprayer sanitation is a time-consuming and distasteful task.
Methods vary, but they generally span from the classic triple rinse (30-45 minutes) to a full tear-down and decontamination (many hours and likely an overnight soak). The operator decides how much time and effort to invest depending on the chemistry they’ve just used and the crop they intend to spray next. Learn more about the power of dilution in this article and in this article.
Unfortunately, two facts are certain:
At minimum, operators should rinse the sprayer at the end of each day… and they generally don’t.
It is only after spraying a sensitive crop that the operator truly knows whether the sprayer was cleaned sufficiently.
Continuous Rinsing
We’ve promoted Continuous Rinsing as a viable alternative to Triple Rinsing in previous articles (see here and here). Executed correctly, the method:
greatly reduces the time required,
is as effective,
eliminates operator exposure, and
reduces potential environmental contamination.
Continuous rinsing requires the installation of a dedicated “rinse pump” to transfer clean water to the product tank from the rinse tank via the wash-down nozzles. This permits the main product pump to operate simultaneously, emptying the product tank and spraying the rinsate out the boom.
Imagine your sprayer empties at the end of the row. You position the sprayer at a headland or a row you sprayed earlier. A toggle switch in the cab engages the rinse pump and the wash-down nozzles start spraying clean water into the product tank. You then resume driving and spray until the rinse tank is empty. During the process, any solution in the return/bypass line is quickly diluted, and any standing volume in the system is displaced by clean water.
It takes five minutes and you never left the cab.
Remember: Rinsing can dilute residue to ~2-5% in most of the sprayer plumbing, but it is not intended to replace the more rigorous decontamination process. Closed circuits, filters and dead-end plumbing can still harbour residue >15%.
Installation
Working with GreenLea Ag Center in 2017, we installed a Continuous Rinse system on a Case IH Patriot 4440. It has a 1,200 gal. product tank, a 140 gal. rinse tank and a 120 foot boom. A parts/price list for the Patriot installation appears at the end of this article.
Additionally, we have included the parts/price list from our 2016 HJV Equipment installation on a RoGator 700, which had a 700 gal. product tank, 50 gal. rinse tank and a 90 foot boom.
Still further, we have included three homegrown solutions from operators that developed their own continuous rinse systems.
Sizing the Rinse Pump
It is very important that the rinse pump has the capacity to operate the wash-down nozzles and still supply clean water at a rate approximately equal to the rate at the boom. Basically, “in must equal out”. If the rinse pump supplies too much clean water, the volume rises in the product tank and efficiency is reduced. If it cannot supply enough, the main product pump will lose suction and not function correctly.
We installed a Hypro 9303C-HM1C centrifugal pump (max flow rate of 114 gpm at 130 psi), matching the make and model of the exiting product pump. A length of channel was installed on the chassis to mount the pump and close-coupled hydraulic rinse pump motor, and a valve block.
Really, electric pump installation is easiest. An alternate pump that has been used is this one from Pattison Liquid. For added benefit, it’s a chem transfer pump that can handle the pesticide formulations. If the pump doesn’t give enough flow, a second one can be installed parallel to double the flow.
Hydraulics
Let’s being with advising caution: If you are uncertain about your hydraulic capacity (and tightly designed systems rarely have extra) then consult with a manufacturer-certified service technician, or consider an electrical alternative.
For the Patriot, the auxiliary hydraulic circuit was used to drive the hydraulic rinse pump; we piggy-backed off of that existing system. In this case, Continuous Rinsing increased the load on the auxiliary hydraulic circuit, but only marginally, so performance was acceptable.
We drew that hydraulic flow directly from the auxiliary pump output using a ‘T’ piece to ensure full pressure was available when needed. Then we broke into a common low pressure return manifold using another ‘T’ piece to provide the return flow.
Originally, we were concerned that robbing too much hydraulic flow could compromise sprayer operations. We therefore exchanged the hydraulic motor that came with the pump for one that required less hydraulic flow. However, the pump operated at such a high speed that the rinse tank was drained in two minutes! We felt this would not give the operator enough time to make minor adjustments (see the “Avoid Airlock” section later in the article). We also felt the rinsate would not have enough time to hyrdate any residue in the tank and lines. We therefore returned to the motor that came with the pump, slowing the pump and bringing our rinse time to approximately five minutes.
We installed an on/off hydraulic control valve block and solenoid controlled by a toggle switch in the cab. When the rinse switch was engaged, 12 volt DC opened the solenoid, allowing hydraulic oil from the auxiliary pump to turn the rinse motor, which in turn powered the rinse product pump.
Avoid Airlock by Balancing Flow
While Continuous Rinsing works well with an unbroken stream of clean water, there is demonstrated benefit to allowing the pump to draw a small amount of air. The bubbles are reputed to scrub the lines more effectively than water alone. It is possible that the new Hypro 9307 series centrifugal pump, which claims to eliminate dry run, would facilitate this.
However, avoid excessive cavitation or airlock of the main product pump. This will damage the pump seals and interfere with pump suction. If the main product pump is a piston-diaphragm pump, avoid losing the prime by letting a small volume of rinse water build up in the product tank before spraying the rinsate.
Maintaining the balance between the supply from the rinse pump, and demand by the product pump, will take careful trial and error. If the sprayer employs a rate controller, speeding up or slowing down travel speed is a means for making adjustments to match the two flows. Alternately, an operator can adjust the pressure regulator manually. Remember, the nozzles won’t need to work optimally so you have the option to use fairly low pressures to match flows.
In the case of an operator applying 28-0-0 using dribble bars or fertilizer nozzles, there is likely too much flow at the boom for the rinse pump to keep up. While we have not tried it, but as long as there was sufficient volume in the clean water tank, it might be possible to rinse the boom section by section, starting with the outside sections and moving in towards the centre.
Lessons Learned
The installation was a learning process, during which we noted the following:
At first, the rinse tank slowly emptied through the rinse pump, even when it wasn’t in use. We prevented this by installing a 10 psi check valve between the pump and main tank.
The rinse pump ran dry and burned the seals when the operator forgot to turn it off after the rinse tank was empty. We considered a timer or alarms to prevent this, but chose to install a level sensor (essentially a float) which would cut the 12 Volt DC feed to the on /off solenoid, effectively turning the system off when the rinse tank was empty. Note: the sensor is not in the parts list – it was purchased for ~$10.00 CAD from Amazon.
When deciding where to draw hydraulic flow to run the rinse pump, we first tied into the main hydraulic circuit (i.e. not the auxiliary). This negatively affected both steering and boom control. Beware drawing flow from critical safety systems such as steering.
Future Development and Other Advantages
GreenLea was exploring an option to use the rinse pump to bypass the product tank, and flow directly to the boom. This can be accomplished by teeing an electrical 3-way ball valve just after the pump to allow flow directly from the rinse tank (see dashed line in the flow schematic shown earlier in the article). Imagine being rained out, or having excess mix left in the tank at the end of the day. This system would allow the dilution of any corrosive chemical from a sensitive precision application system without losing or contaminating the spray tank. It should be noted, however, that high precision spray systems (e.g. AIM Command, Pro and Flex) would still require the operator to open the boom flush valves manually to allow the boom purge.
Growers have suggested the system might also be used to get a sprayer to end of a row if it threatens to run empty before completing the pass. A small volume of clean water added to the tank would displace the 15-30 gallons of unusable volume and stretch the application. Be aware that this would also dilute the product due to the agitation/bypass and should only be considered when a minute or less of additional spray is required.
Homegrown Solutions
Tyler Patriot (Electrical)
David Kucher (@DavidKucher) from Saskatchewan installed Continuous Rinse on his Tyler Patriot (75 foot boom, 800 gal. product tank).
Here’s what he had to say:
The rinse system I was using on my sprayer previously involved a lot of time and effort. Plus, the quality of job it did was sometimes imperfect (I keep pictures on my phone of a canola crop that was damaged because of a poor rinse job from a few years ago). The old system used the main product pump to rinse, so there was a bunch of valves under the sprayer that needed to be turned, and the pump had to reprime for each rinse. It was tedious.
Uncertain about the hydraulics, David elected to use an electrical pump, but had difficulty finding one that would produce enough pressure and flow. Most electric pumps were too small and it would have taken more than one, plumbed in parallel, to achieve the volume numbers required. However, David found a high-flow 489G-95 AMT High Head Washdown Pump (1 HP, 1-1/4×1 IN/OUT, 12 VDC,Cast Iron,Buna-N) which he got from the US for about $1,200.00 CAD. Max flow was 56 gpm.
Note: In 2020 this pump model changed to the 12DC-95.
He removed the majority of plumbing, valves, and related complexity from the old rinse system. The Continuous Rinse was comparably simpler and isolated from the rest of the sprayer plumbing. It just involved a fill line from his two clean water tanks, the new rinse pump, and the existing rinse nozzle inside the product tank.
When the product tank empties, David holds down a push button dead-man switch he installed to activate the rinse pump. If he wants to do a more thorough job, he flushes the product tank and plumbing for about two minutes, then stops, gets out and opens the boom end valves. Then he climbs back in and does another one minute flush.
Approximately 30 gallons of water go through on each flush and my only issue is that I waited so long to install the system.
Author’s note: Positive displacement electrical pumps (which have zero risk of seal loss) are reasonable alternatives to centrifugal pumps. Depending on the size of the sprayer, multiple pumps plumbed in parallel can provide sufficient flow. We elected to use two Hypro electric roller pumps (model 4101 N-H) for the 2016 RoGator 700 installation. Cheaper, low amperage 12V diaphragm pumps from Delevan and FLOJET with capacities of 5-8 gpm are also available.
John Deere 4830 (Hydraulic)
Russ Enns (@EnnsFarms) from Saskatchewan installed a Delavan HD Magnum 125 hydraulic driven pump (1-1/4” suction, 1” discharge, 5-7 gpm of hydraulic flow). He mounted it on the same mounting plate as the main product pump, just on the opposite side, using the same bolt holes.
It was tied hydraulically to the main product pump, so the rinse pump could only run when the product pump was operating. The hydraulic supply from the sprayer went through an electric/hydraulic block via a solenoid resting in the closed position. A rocker switch in the cab used 12V to activate the rinse pump from the cab. Return hydraulic pressure from the rinse pump was tee’d into the main solution pump hydraulic return.
The clean water intake for the rinse pump was tee’d into the factory rinse tank. The discharge side of the rinse pump was plumbed to a check valve and tee’d into factory tank rinse system. Here’s the discharge line, check valve and tee into factory rinse (below).
Russ mounted a large pressure gauge on front right axle to monitor rinse pressure. It’s easy to see from the cab, and easy to tell from the pressure when the rinse tank is empty.
In this case, Continuous Rinse is used in tandem with an Accu-volume tank gauge so Russ could monitor the level in the main product tank from the cab. Depending on the nozzles being used, he found that the rinse pump supplied clean water faster than the rinsate could be sprayed.
So, after finishing a field (or changing chemical, etc.) Russ turned on the rinse system while spraying the rinsate out on the field. The Accu-volume alerted him if clean water was accumulating in the product tank. If it got to ~20 gallons, he would briefly suspend the rinse pump while spraying to allow the level to drop. Then, he would start the rinse pump back up. He repeated this process until the clean water tank was empty.
Russ had many of the main components on hand, but estimates replacement value at ~$1,200.00 CAD. He noted that while installation was straight-forward, he originally piggy-backed the rinse pump’s hydraulic supply off the main solution pump, and it didn’t work correctly. We did that too, Russ 🙁
“Time savings and environmental considerations are the biggest benefit of this system to me. Being able to finish spraying a field, and immediately start rinsing and spraying the diluted solution is a huge time saver. I feel it’s a far more thorough rinse and a better/quicker dilution rate compared to how I previously handled rinsing and spraying out the diluted solution. Another benefit is that even though it’s plumbed into the factory rinse, the factory rinse system can still be used normally if for some reason the continuous rinse pump quits.”
Gregson Trailed (Electrical)
Continuous Rinse isn’t only for grains and beans. Matthew Droogendyk installed two 12v pumps on his trailed vegetable sprayer that matched the flow of the main pump. They had an electrician install a box for switching the the pumps and two solenoid valves on at the same time.
They noted an issue when trying to prime the main pump after emptying the tank. If the tank was sprayed completely empty, the main pump took time to get primed again. This affected rinsing time as well as the balance between supply and demand. Through trial and error they determined that running the rinse pumps for 1 minute (~15 gal) gave enough time to rid the main pump of air. Then the flows matched at about 15 gpa. Re-priming took about 5 minutes, and then an additional 2 or 3 to rinse using about 45 gallons of clean water. They found there was no need to replace their original tank rinse nozzles.
Tank Rinse Nozzles
One of the challenges of installing continuous rinse is ensuring the tank rinse nozzles are capable of rinsing the entire solution tank interior at potentially low pressure and low flow. In 2019, Lechler released the ContiCleaner range of rinse nozzle. Four ISO colour-coded nozzles capable of operating from 2-5 bar (29-72.5 psi), with flows from 6.5-32.3 L/min. (1.7-8.5 gpm). This will enable operators to better match the rinse nozzle(s) to the clean water pump. Be aware they are very difficult to source in North America. We tried and weren’t able to get them.
Parts / Price List
The following two parts/price lists are in Canadian Dollars. They do not include tax or labour and prices change depending on where and when parts are purchased. As you have read from the operators that installed their own Continuous Rinse systems, there are many possible solutions, so these lists are provided only for reference. Click the link to download a PDF.
Before contacting them, have the following information on hand:
Sprayer tank volume (both product and rinse, if applicable)
Boom length
Nozzle spacing
Largest nozzles mounted/used on the sprayer (excluding fertilizer nozzles)
Power available on sprayer (e.g. 12V available? Max amp? Hydraulic capacity?)
Thanks to Russ Enns, David Kucher and Matthew Droogendyk for sharing their install stories. Thanks to Adam Beaumont and Ehrin Frid for the Case IH and RoGator installations, and to Mike Cowbrough (@cowbrough) of OMAFRA and the Ontario Soil and Crop Improvement Association for collaborative support.
Next to sprayer math, cleaning the sprayer is one of the more distasteful aspects of airblast spraying. It’s time-consuming, you never really know when you’re finished, and sprayer manufacturers and pesticide labels offer only limited guidance.
Clean sprayer rinsate often looks and smells exactly like contaminated sprayer rinsate.
When airblast sprayers are not cleaned as often or as thoroughly as they should be, it creates problems:
Unnecessary operator and environmental exposure.
Residue in (or on) the equipment can damage sprayer components.
Carry-over can deposit damaging or unlabelled residues on crops.
Keeping the airblast sprayer clean, inside and out, as part of the spray day. Ken Bell is pictured giving his FMC a bath. This picture was staged – he normally wears PPE and so should you.
Dr. Tom Wolf (Agrimetrix Research and Training), defines cleaning as two processes. Rinsing is the dilution of any remaining spray solution. Cleaning is rinsing with additional steps to decontaminate sprayer components (e.g. filters, nozzles).
Rinsing
1. Rinse ASAP
Don’t let residue sit in (or on) the sprayer, even if you plan to use the same product the next day. Multiple studies have shown that products adsorb onto, and absorb into, plastic and rubber parts. They form hard-to-clean residues when left to dry.
Think about cleaning oatmeal or egg yolk off dishes – it’s far easier if you clean them before they dry. Rinse right away, while the sprayer is still wet.
2. Minimize the volume remaining in the sprayer
Experience, sprayer math, and familiarity with airblast sprayer design helps minimize the volume remaining in the sprayer. Rate controllers and volume-monitoring systems (e.g. Ontario’s Accu-Volume) provide real-time feedback so the operator can speed up or slow down to empty in the right place. Minimizing any remaining volume makes rinsing far more effective.
Even an “empty” sprayer can still retain several litres of standing volume in the sump and lines. Operators should know this volume. Never Drive-and-Drain to empty standing volume onto the ground.
Standing volume from the booms allowed to drain to a holding tank via the bottom nozzles.
3. Dilute the remnant: The Triple Rinse
Rinsing the system multiple times with low volumes (aka The Triple Rinse) is more effective at reducing pesticide concentration than a single, high-volume rinse. See for yourself using this clever dilution calculator.
Once the sprayer is “empty”, use clean water to fill the tank to 10% of its capacity (or add 10 parts water to one part standing volume) for the first rinse. The use of such low volumes may not be possible with centrifugal systems where the tank must be filled above the top of the pump for priming. Know your sprayer design.
Agitate and circulate it through the entire sprayer for a few minutes. Spray out the rinsate and repeat the process two more times. Where do you perform this? Where does the rinsate go? Read on.
A wooden sprayer tank. You know that had to be tough to clean.
Where does the rinse water come from?
Nowadays, all airblast sprayers should include an onboard tank-rinse system consisting of a clean water tank and tank-rinse nozzles inside the tank. They may even include a pressure wand to rinse the exterior.
Sadly, most airblast sprayers do not have these features. But, aftermarket rinse kits are available. If you are considering installing a rinse system, check out the continuous rinse system.
Left- Product-pump-powered water tank, Right- external-pump-powered water tanks. Images from Paolo Balsari’s (DiSAFA) “Sprayer Cleaning: Importance and Phases” at AAB Sprayer Cleaning Workshop, Oberbozen, Italy. October 2019.The Hol features a separate 150 L tank to supply clean water to its automatic tank rinse system.
Alternately, the clean water for this process can be carried on a support vehicle or sourced from holding tanks strategically-located near the planting.
Where to rinse
Precautions must be taken to ensure rinsing is performed away from wells or open water. It is best to perform the triple rinse in the crop that was just sprayed. The dilute rinsate can be flushed through the lines and sprayed out through the nozzles onto the crop. You can choose to overspray treated areas again at a lower dose (label permitting), or use a hedgerow or target row that has been set aside for this purpose.
As regulatory agencies concerned with environmental contamination re-evaluate chemistries critical to horticulture, it becomes even more important for airblast operators to manage rinsate responsibly.
While it is best to rinse the sprayer exterior in the planting as well, most return to the farm. Too often, the entire rinsing procedure takes place on-farm, on crushed gravel. This creates point-source contamination: a leading source of off-target pesticide movement. Washings should be secured (e.g. on an inflatable or permanent loading/mixing pad.
Cleaning an airblast sprayer on an inflatable pad. Images from Victoria Nelissen’s (pcfruit, Belgium) “On-farm systems to avoid point pollution” at AAB Sprayer Cleaning Workshop, Oberbozen, Italy. October 2019.
In Europe, operators are encouraged to collect contaminated rinsate for safe disposal. There are four systems in use:
Bioremediation – Employs a bio-active matrix (E.g. Biobed).
Evaporation / Dehydration – Residue following evaporation is collected and disposed of (E.g. Heliosec).
Physico-chemical – A combination of filtration and active carbon.
A complete cleaning is required prior to long-term storage, or when residues from previous applications are known to cause physical or chemical antagonism with scheduled applications. Perform the following steps after a complete triple rinse:
One. Remove the suction and in-line screens. Remove nozzle strainers and nozzle tips. These will be inspected and cleaned shortly.
Two. Fill the tank about 1/2 full of water and add an appropriate tank cleaning adjuvant. For example, ammonia at 3%/100L water will raise the pH and helps remove those products whose solubility benefits from this. A detergent at 1.0 kg /150 L water will remove the oily layer formed by EC formulations. Commercial cleaners like All Clear or Cleanout conveniently combine these properties in one jug. Be aware that adding a surfactant or a commercial cleaner can generate a lot of foam, so have de-foamer handy.
Note: Ammonia cleaner products do not “neutralize” pesticides; they raise the pH, improving the solubility of some products. Do not use chlorine bleach! It is not as effective a cleaner as ammonia and can form chlorine gas when mixed with ammonia-containing liquids.
Three. Collect a bucket-full of cleaner solution from the tank. Using a brush, clean the suction and in-line screens, and the nozzle strainers and tips.
Four. Meanwhile, agitate and circulate it the cleaner solution through the entire sprayer for five to 10 minutes. Open and close any lines or valves during this process to ensure everything is exposed to the rinse.
Five. You might spray a small volume through the booms, but drain the vast majority through the plumbing system. Collect some for cleaning the exterior of the sprayer.
Six. Clean the exterior of the sprayer. High pressure washers and scrubbing with a push broom works well. Studies in Europe have shown the vast majority of residue is found on the sprayer head (i.e. fan outlet and boom area).
Pressure washers are handy tools on a farm, and they’re fun to use, too. However, they can cause a great deal of damage if they are used to wash delicate things like engine parts, electronics housings, or sealed bearings. Use caution when power washing an airblast sprayer.Relative external contamination on a low profile axial airblast sprayer. Image from Paolo Balsari’s (DiSAFA) “Sprayer Cleaning: Importance and Phases” at AAB Sprayer Cleaning Workshop, Oberbozen, Italy. October 2019.
Seven. Rinse it all off. Replace all parts unless preparing for long-term storage.
This article was co-developed by Mike Cowbrough, OMAFRA Weed Management Specialist in Field Crops
Why scrub filters?
Why do we ask you to manually scrub residue from sprayer filters and housings before changing chemistries? Here are three reasons why rinsing in-place may not be good enough:
There is potential for biologically-active levels of residue to persist in filters, even after a triple rinse, that could harm the next crop sprayed.
Persistent residues could cause physical antagonism with the chemistry you use next. This can cost time and/or efficacy should it plug filters and nozzles or reduce spray uniformity.
Persistent residues could cause chemical antagonism with the chemistry you use next – even several batches later. This could harm crops when the residue carried over from a much earlier application suddenly becomes soluble again thanks to detergents or pH adjusters in subsequent tank mixes.
An experiment
To some, the previous statements may seem excessive. Many sprayer operators claim that scrubbing filters is time consuming, or that they’ve never had a problem before, or that the tiny amount of residue they see in the filters after rinsing couldn’t possibly cause damage. We decided to test the efficacy of rinsing filters without removing them.
We constructed a table-top system that could circulate chemistry through a 50 mesh filter. Think of it as a scaled-down sprayer that returns solution to the tank rather than spray it out. It replicates what the line filters on a larger sprayer might experience during a typical spray day.
Table-top system to circulate spray mix at 1 gallon per minute through a 50 mesh filter.
The method
The tank (i.e. the bucket) would be filled with a tank mix and circulated through the filter to replicate a spray day. The contaminated filter could then be sampled to establish a baseline, and then alternately contaminated and rinsed in place to compare how much residue remained. Specifically, we would drop the filter housing and scrub all surfaces in 500 ml of water to collect any and all residue.
Each sample collected would be poured through a filter for a visual check of residue. A small volume would be reserved to be sprayed on soybean and white bean seedlings as a bio assay of activity.
The process
We used Sencor (metribuzin) mixed at a rate that represented the low end of the label: 250 grams of product per acre at 5 gallons per acre. Not knowing what to expect, we circulated the solution through the filter for 20 minutes pumped at a rate of 1 gallon per minute and peeked into the tank.
After 20 minutes of circulation, Sencor began to foam.
Seeing that we were creating foam, we decided to add defoamer. Then we peeked into the filter housing to see what had accumulated so far.
Very little residue was found on the filter or in the housing after 20 minutes of circulation.
Finding very little in the way of residue, we chose to let the system circulate for an hour. We felt this would represent a single real-world tank’s worth of product. Since we’d added defoamer, we decided it was safe to leave the lab and let the system circulate…
Foam overs: No fun in the field and no fun in the lab.
Despite having added defoamer, we had a mess to clean up. When we opened the bucket we noted all the product clinging to the lid (see below). We collected some of this scum to replicate what might be clinging to parts of the spray tank that are not adequately covered by rinse-down nozzles. We then dropped the filter into 500 ml of water and scrubbed the housing and filter to collect any and all residue.
Collecting residue from the bucket lid to replicate what might remain in a tank that is not sufficiently rinsed.
We then added additional defoamer and checked in regularly as we circulated the mixture for several hours to replicate a full day of spraying. This time when we checked to see how much residue we had collected, found a surprising amount.
Residue following several hours of circulation, prior to triple rinsing with water.
We replaced the filter and performed a triple rinse with water before dropping the filter to collect our residue sample. As shown below, the triple rinse cleared much of the residue, but trace amounts were still visible.
Residue following several hours of circulation and a triple rinse with water.
Dawn Detergent and the 5 Second Squeeze
We refilled the tank with Sencor and defoamer and circulated it for several hours to once again contaminate the filter. This time, however, we added detergent to the second rinse. We did this in response to claims that Dawn dish detergent removed residues from dry products such as Atrazine without having to drop the filters.
A former agrichemical rep explained that the practice likely originated in Western Canada some years ago when several growers suddenly experienced physical incompatibilities with a particular batch of dry product. It was suspected that the problem was due to abnormally cold temperatures during mixing, but the result was that many were left with solids in the tanks that could not be flushed.
Ionic surfactants are found in “cheap and nasty” shampoos, dish detergents and car care products. They can be tough on the skin, but they are of higher surfactantcy than NIS. And so, agrichemical reps bought pallets of Dawn dish detergent (Branded “Fairy” in the UK) from big box stores and found it broke the solids down sufficiently to flush the tanks. From there, it is likely growers started adding it during the rinse to facilitate cleanout. But, is the “Five second squeeze” a myth or does it work?
Results
Adding Dawn detergent to the second rinse reduced visible residue in the filter housing and on the plastic sides of pop bottles that stored the rinsate.
We saw a visible reduction in the filmy residue left behind by Sencor in the filter housing and on the walls of the pop bottles used to store the rinsate. It was easy to see why the 5 second squeeze appeared to improve matters… but was there enough residue to still there to cause trouble?
Rinsate filtered through red cloth for a visual check of residue.
We poured the rinsate from each sample through red cloth. There was little or no visible evidence of Sencor in the sample taken from the lid of the filter following an hour of spraying (left), or our baseline sample of a filter contaminated after an hour of circulation with no rinse (second from left). There was a great deal in the sample from the filter following “a day’s spraying” and a triple rinse (second from right), and less in the triple rinse containing detergent (right). These last two conditions are compared below.
Following several hours of spraying, residue following a triple rinse with water (left) and a triple rinse with detergent in the second rinse (right).
A volume of the rinsate from each sample was reserved for bio assay on soybean seedlings. The filter in the spray booth was cleaned thoroughly between conditions.
The following images show that even when there was little or no visible residue, there was still sufficient activity remaining to injure, or in the case of the triple rinse with water, kill soybean seedlings.
Summary
Bear in mind that this is a single experiment with a single chemistry, but it does support the following observations:
Always rinse the sprayer as soon as possible and pay attention to dead-end plumbing and filters. Diligence is a function of knowing what was sprayed last, what is coming next, and the sensitivity of the crops being sprayed.
Cleaners do not decontaminate – they loosen residues to make rinsing more effective. In our experiment, Dawn detergent appeared to reduce residue and that will keep you spraying plug-free for longer. But, the bioassay showed sufficient activity remained to cause carry-over damage.
A triple rinse with water may be insufficient to remove residue from filters. Even if the residue left behind does not cause damage in the next crop sprayed, it can persist and has the potential to react antagonistically with subsequent sprays.
Bonus: Pro Tips
Not long after publishing this article, we were contacted by a grower who had difficulties with clay-based products plugging up his filters. It took a carry-over incident to convince him he needed to address the problem, so he installed $20 ball valves at the bottom of the filter housings. This isn’t as good as dropping and scrubbing filters, but opening and closing the valve under pressure during rinsing blew the filters clear of visible residue. Others have noted similar modifications on the pump of their tender truck to clear the filter of algae.
Other options include a hydraulic-style ball valve (stronger than plastic). Or, install a gator lock cam after the valve and insert a plug so if it’s accidentally opened it won’t dump the tank. Just keep a hose in the toolbox and insert it when you need to flush. Finally, one grower added a Thompson strainer to the sprayer and removed the screens from the Banjo Y’s. He ran a 1″ hose from the Thompson to a valve by the work station and cracks it open as part of every rinse.
A cheap and effective solution for clearing filters of residue. Not as good as dropping and scrubbing, but a great compromise.Ball valves tend to protrude below the sprayer, so they may catch high corn. Be careful.
