As the University of Arizona Cooperative Extension advises, it is not wise to run different chemicals through the same garden sprayer since residue often remains, even after a careful cleaning. Even so, it is good to clean your garden sprayer regularly after use, or when switching brands or strengths of pesticides or herbicides, both to keep it running well and to avoid any dangerous combinations of chemicals. Ammonia is effective at neutralizing some herbicides, and cleans and prepares your garden sprayer for use in the next season.
Rinse the garden sprayer out with fresh water, making sure the water drains in a place that will not harm plants and is not within reach of pets or children.
Fill the reservoir tank with fresh water and spray the water back out, continuing to make sure the water runs in an area where it won't harm plants or animals.
Mix together one cup of ammonia in three gallons of water.
Pour the ammonia mixture into the reservoir tank.
Spray a portion of the ammonia mixture out through the sprayer so that it can clean the hose and sprayer as well as the tank.
Detach the sprayer head and submerge it on the ammonia mixture.
Allow the ammonia mixture to sit in the reservoir tank and on the sprayer head overnight, about 18 to 24 hours.
Spray the remaining mixture out of the garden sprayer, so that it runs through the equipment, cleaning it as it passes through.
Rinse the sprayer and tank with clean water.