Cleaning out the sprayer tank — tips

June 15, 2011 - Issue 12

By Tom Wolf

We all know the importance of cleaning out a sprayer tank and boom. It protects a sensitive crop. It protects people working with the sprayer. It protects the sprayer and its components. But cleaning the sprayer is a pain.  Some herbicide label instructions are cumbersome, requiring many flushes with full tanks of water. Many applicators look for shortcuts and hope they get away with it. But it doesn’t have to be hard guesswork. The following is a checklist that may help.

Be prompt and thorough

Remove pesticide from mixing and spray equipment immediately after spraying – it makes the job easier. The main areas of concern are the tank wall, sump, plumbing, and filters. First, spray the tank completely empty while still in the field. It’s OK to cover previously sprayed areas – all herbicides must be crop-safe at twice the label rate to be registered by the PMRA. Reduce the rate to be certain. Second, add 10x the sump’s remnant of clean water, circulate, and spray it out in the field as well. Repeat. These two rinsing steps will take care of the majority of the cleaning and won’t take very long. Having a clean water tank on the sprayer and a wash-down nozzle makes this job easier.

Visual inspection

Herbicide residue may precipitate out of solution in some parts of the sprayer or plumbing. A thorough visual inspection can identify these problem areas and ensure that they are cleaned properly.

Tank wall

Removal of residues from tank walls is best accomplished with a direct, pressurized spray. Make sure all parts of the wall have been in contact with clean water. Use a wash-down nozzle if it provides complete and vigorous coverage of the interior tank surface.


Empty the sump as completely as possible by spraying it out. Any spray liquid or herbicide concentrate remaining in the sump area will be re-circulated in the sprayer. In this case, the only way to remove the remaining herbicide is through dilution by repeatedly adding water and each time draining the sump as much as possible.


Plumbing can be a significant reservoir of herbicide residue. Residue removal from plumbing can be achieved by pumping clean water through the boom while ensuring that all return and agitation lines also receive clean water and all residue is flushed out. This may require opening and closing various valves several times, and repeating the process with new batches of clean water.


The most effective use of a volume of rinse water is to divide it equally across several repeat washes.  For example, a single 600 gal wash is as effective as two washes with 70 gallons each, and three with 30 gal each, assuming a 10 gallon sump remainder. More wash cycles allow for less water in total.


Nozzle screens and in-line filters can be a significant reservoir for undiluted or undissolved herbicide and are one of the most overlooked parts of sprayer decontamination. Remove all filters and nozzle screens and thoroughly clean these with fresh water. Run clean water through plumbing leading to the screens.

Nozzle bodies

Multiple nozzle bodies may represent a source of concentrated herbicide.  When cleaning a spray boom, rotate through all nozzles in a multiple body to ensure clean water reaches all parts of these assemblies.  Remove screens that may have been used with herbicide, even if just for a short while.

Tank cleaning adjuvants

Adjuvants such as ammonia can assist the tank decontamination process.  Ammonia does not neutralize herbicides, but it does raise the pH of the cleaning solution which helps sulfonyl urea herbicides dissolve.  When decontaminating after use of an oily (EC) formulation, the use of a wetting agent such as AgSurf will assist in removing oily residue that may trap SU herbicide on tank and hose material.  Commercial cleaners are available.

Rinsate disposal

Always spray out the tank in the field.  Do not drain the tank while stationary unless you are certain it is free of pesticide and that you are away from sensitive areas and waterways.

A new area of research that addresses this issue is biobeds.  Biobeds contain a mixture of soil, compost, and straw which fosters microbes that are capable to degrading pesticides.  Initial results show that placing dilute pesticide waste into biobeds breaks them down more quickly and prevents them from reaching ground waters more effectively than placing them onto soil.

Sprayer cleanout may never be the best job on the farm.  But looking at it in a smarter way can prevent frustration and save time.

For more on sprayer tank clean out instructions, read page 14 in the Introduction section of the Saskatchewan and Manitoba Guides to Crop Protection.

*This article was originally written for SSCA’s Prairie Steward newsletter. It is posted here with permission from the author.

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