How to Calibrate a Homemade Lawn Sprayer

Plot out and mark a test area where you can spray water on approximately 200 square feet.

Pour a measured amount of water into the sprayer tank.

Spray the area uniformly with water.

Determine how much water was sprayed by measuring the amount remaining in the sprayer tank and subtracting it from the total amount.

Calculate the sprayer's rate of coverage per 1,000 square feet. If you used one quart (.25 gallon) of water to spray 200 square feet, then the rate of coverage for 1,000 square feet is five quarts, or 1.25 gallons. Label instructions for proper coverage with liquid pesticide and fertilizer are usually expressed in quarts per acre. For smaller areas, conversion to ounces per 1,000 square feet is helpful.

Convert to ounces using this formula: Ounces per 1,000 square feet = recommended quarts of pesticide per acre x 0.73. If the manufacturer recommends a coverage rate of three quarts of pesticide per acre, the amount to disperse per 1,000 square feet is 2.19 ounces. Thus, if the area to be sprayed is 490 square feet, the amount of pesticide to be dispersed over that area = 1.07 ounces.

Fill the sprayer with the amount of water in Step 2. Add the measured amount of pesticide or fertilizer (in this example, 1.07 ounces) and spray the 490-square foot area uniformly.