Cleaning the herbicide residue from your small sprayer is essential to the longevity of the sprayer and the health of your plants. Residual herbicide in a sprayer can accidentally end up on the wrong plant and kill it. And, if left in a sprayer while it is stored overwinter, an herbicide can damage one or more of the parts of the sprayer. Ideally, clean your sprayer after every application of herbicide. Once allowed to dry in the sprayer, herbicides become much tougher to remove.
Check the label of the herbicide. It may contain special instructions for cleaning or loosening herbicide residue in the sprayer.
Flush the sprayer with water. Hot water is best if the herbicide has been in the sprayer for an extended period of time. Empty any liquid contents of the herbicide into the ground in an area with no traffic, no desirable plants and no access to ground water. Then, fill the reservoir 1/4 full with water, and spray the sprayer (again, in a safe location), until all the liquid is expended.
Add a cleaning solution to the reservoir tank. If the sprayer previously contained a sulfonylurea or oil-based herbicide, fill the tank with a solution comprised of 1 oz. of ammonia per gallon of water. Spray the sprayer 10 times (again, spray into a spot with no traffic or desirable plants), and allow it to sit for six hours. Then, spray the sprayer 10 more times, and empty the solution. For all other types of herbicides, replace the ammonia with bleach. However, do not use both. Chlorine and ammonia combine to form chlorine gas.
Flush the sprayer with water again. Fill it 1/4 full with water, and spray it 10 to 20 times. Then, empty out the remainder of the water in the reservoir. Repeat two more times.