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Backpack Sprayer Calibration

Why is calibration important?

Backpack, pump-up and other single-nozzle wand sprayers are often used for liquid treatment application for spot treatments, small areas or home lawns. However, many homeowners do not know how to properly calibrate sprayer output for these types of sprayers. This can lead to improper application of fertilizers, pesticides or other liquid products, which ultimately wastes money and can be harmful to the turfgrass and the environment. An easy method for determining sprayer output is based on a procedure described as the 1/128th-acre method. Follow these simple steps below to properly calibrate your single-nozzle wand sprayer.

Backpack sprayerpng

Backpack sprayer

Steps for setting up a calibration area

Step 1: Mark off an area with the dimensions 17 feet by 20 feet. This area is approximately equal to 1/128th of an acre, or 340 square feet.

Step 2: Make sure the calibration area corners form right angles. To ensure the corners are right angles, measure across from opposite corners. The diagonal line from one corner to another corner should measure 26 feet and 3 inches.

Graphic of example calibration areapng

Measuring calibration areapng

Tip: The 1/128th method is based on a calibration area equaling approximately 1/128th of an acre, or 340 square feet. These steps suggest measuring a 17-foot x 20-foot rectangle; however, you can adjust the dimensions as long as the area is squared and equals approximately 340 square feet (example: a square measuring 18.5 feet x 18.5 feet = about 340 square feet).

Backpack sprayer calibration

Step 1: Read the label of the product you want to apply in order to know the gallons per acre (GPA) of solution (water and product) needed for proper application.

Step 2: Make sure the sprayer and nozzle are clean and working properly. Broken or clogged parts should be replaced. Improperly working sprayers affect calibration and application of products and need to be repaired.

Step 3: Fill the sprayer tank with clean water only.

Step 4: Walking at a comfortable pace, apply water uniformly to the entire calibration area while recording the time in seconds that is required to completely cover the calibration area with water. It may be best to repeat this step several times to calculate an average time.

Step 5: Using a container that measures volume in fluid ounces, collect output from the nozzle for the number of seconds timed in step 4.

Step 6: The fluid ounces collected will equal the application rate of the sprayer in gallons per acre (GPA).

Tip: The speed you walk will affect the calibration. To increase the GPA delivered, decrease the pace when applying water to the calibration area. To decrease the GPA, speed up the pace when applying water to the calibration area.

Measuring sprayer output volumepng

Measuring sprayer output volume

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