Calibrating Your Sprayer
It’s spring and your technicians are out servicing lawns. Do you know what their spraying technique is? Each person has their own walking speed and other characteristics like longer arms that can speed up or deter the time it takes your technician to complete a lawn. How do you decide on the right spray calibration for your technicians?
The first consideration should be the end spray volume desired in terms of gallons per 1,000 square feet delivered. For most lawn care companies, the typical spray rates are:
- 1.5 gallons per 1,000 sq. ft.
- 2 gallons per 1,000 sq. ft.
- 3 gallons per 1,000 sq. ft.
Each spray volume has its benefits. By spraying at a lower volume (like 1.5 gallons per 1,000 square feet), you have more production per tank full. This means your technicians are dealing with less weight in their truck and higher production in square feet per tank. However, by spraying at a higher volume, you ensure that you are applying a better coverage of the plants and soil. Keep in mind that at Holganix, we’d like to see you spraying no less than 1.5 gallons per 1,000 square feet.
Once you’ve selected the spray rate you’d prefer to use, there are three additional measurements you must consider for spray calibration. The three measurements are:
- Pace – walking speed
- Width of spray pattern
- Volume of spray coming out of the spray gun
Any of the above variables can be changed. This means that there are numerous ways to spray and deliver the proper spray volume per 1,000 square feet. However, there are also many ways to deliver the wrong amount of spray. How do you calibrate your spraying correctly? Follow the example below for instructions.
Overview – All turf is actually being sprayed twice. This is referred to as double overlap coverage. This is the same technique for granular fertilizer. Always spray back to the center of the prior pass.
Part A – Choosing Your Measurements
We are going to calibrate a sprayer to deliver 1.5 gallons per 1,000 square feet.
Let’s do the math:
- Start with Pace – Walking Speed. In this example, we will select the average walking speed of 3.25 mph or 143 feet per 30 seconds. Time how long your technicians walk within 30 seconds.
- Width of Spray. In this example, we have opted for a 7-foot-wide spray pattern. Have your technician do a sample spray on concrete and measure the width of his spray pattern.
- Volume of Spray. 143’ length x 7’ width = 1,000 square feet covered by your technicians every 30 seconds. However, keep in mind that all turf gets sprayed twice. That means you are achieving an effective coverage of 1,000 square feet every 60 seconds. Since 1.5 gallons per 1,000 square feet is the desire spray volume result we selected, we need to calibrate the sprayer to deliver 1.5 gallons in 60 seconds. In other words, every 60 seconds, you will be spraying 1.5 gallons per 1,000 square feet.
Now we know that we need to calibrate the sprayer to deliver 1.5 gallons in 60 seconds, which brings us to Part 2. See the attached chart to make this math easier.
Part 2 – Calibrate Your Sprayer
To calibrate your sprayer, time yourself spraying into a measuring beaker to determine the gallons or ounces your gun releases. Remember, for the above scenario, you should calibrate to 1.5 gallons (192 oz) in 60 seconds. Keep these tips in mind:
- Adjust the RPM of the engine as needed. An increased RPM will increase the flow rate.
- Adjust the pump pressure as required. An increased pressure will increase the flow rate. Adjust this last; after all, the less work the pump needs to do, the longer it will last. Try to start with the pump above idle.
- Perform tests until the results are within your target range.
- We also recommend performing a “bucket” test at least once a week to ensure the settings are correct.
For a quicker spray test, instead of collecting and measuring the spray for 60 seconds, collect and measure for 15 seconds. In this scenario, we would want to calibrate to 48 ounces in 15 seconds. Here is the math:
1.5 gallons divided by 4 (1.5 gallons x 128 oz =192 oz / 4 = 48 oz) and 60 seconds divided by 4 = 15 seconds. So, 48 ounces in 15 seconds can be used for quicker calibration.
Note: some pumps may deliver an initial higher pulse when the trigger is first pulled on the spray gun. To compensate for this, it is recommended that you spray for 5 seconds into one bucket then transfer into a second bucket/beaker for the next 15 seconds, which should allow for a more accurate spray rate portrayal.