How to Use a Pressure Sprayer. Fertilizing or applying pesticides can be done with a pressurized sprayer. Sprayers come in either plastic or metal, and in a wide range of sizes; some backpack sprayers have a pump handle so you can keep up the pressure inside the tank without having to take off the backpack. Here's how to use these tools.
Test the sprayer every time you use it by first filling it with water. Pump up the pressure and test to see that the nozzle is not plugged. Release the pressure by unscrewing the lid slightly. Remove the lid.
Leave the testing water in the tank.
Measure the amount of chemicals exactly. More is not better in the case of garden chemicals. You can do serious injury to plants by overfertilizing or adding too much herbicide.
Add the chemicals to the water in the sprayer. Rinse the measuring device by adding more water to the tank to make up the balance.
Screw the top on, being careful not to cross the threads. Tighten so that the pressure will not escape from the tank.
Pump the handle to increase the pressure inside the tank.
Spray the plants, making sure to cover both upper and lower sides of the leaves. There needs to be visible moisture on the leaves for the applied material to work.
Spray out all of the material in the tank. Don't leave any unused chemical in it.
Clean the empty tank over a dirt area, never over concrete or in a sink. Rinse the tank three separate times, spraying clean water through the nozzle each time.
Store with the cap off in a protected area away from light and heat.