A handheld spray gun operates off a truck-mounted pump and spray tank. Developing a consistent walking speed, arm motion, and uniform spray pattern are the keys to successful application with a hand-gun sprayer. An overlap of one-half swath width (sprayed band) is needed for uniform coverage of parallel passes. Practice on a paved surface using water until your coverage pattern is even. Then set the pressure of the sprayer following the manufacturer’s guidelines for the pump and nozzle before calibrating the sprayer.
To calibrate a spray gun
Step 1. — Divide 1,000 square feet by your swath width to determine the distance of the test course
Step 2. — Spray the test course with water using the technique you will use for the application. Begin spraying just before you enter the course.
Step 3. — Record the number of seconds it takes to spray the test course. Do this at least three times to get an average time to use for calibration
Step 4. — Spray into a bucket for the average number of seconds from Step 3. Measure this amount and convert to gallons.
Step 5. — Amount of water collected is the spray gun output per 1,000 square feet. To determine output per acre, multiply output per 1,000 square feet by 43.56
1. For a swath width of 5 feet, mark a test course that is 200 feet long
(1,000 square feet divided by 5 = 200 ft)
2. Average time in seconds to spray 200 ft. test course:
77 + 79 + 78 = 234
3. Gallons sprayed into bucket in 78 seconds: 5.25
4. Output = 5.25 gallons per 1,000 sq. ft. or 228.7 gallons per acre (5.25 × 43.56)
Note: If your calibration output is not within 5 percent of the label rate, adjust the nozzle or pressure. Recalibrate until your output comes within 5 percent of the label rate.
Compiled by Wayne Buhler, PhD.