One of my least favorite things about spraying is filling and mixing the chemical in the tank. So, I prefer to use a backpack sprayer when spraying my yard. That way I know I can cover everything with one tank full. But, it got me thinking, just how much area can a backpack sprayer cover? So I did some checking.
A backpack sprayer can typically cover between 1000 and 10,000 square feet. The total area it can cover depends on the application rate of the product being sprayed as well as the volume of the sprayer tank. Other factors that affect how much area a backpack sprayer can cover are walking speed, nozzle size, nozzle swath width, and the pressure at which you spray.
With all the variables that come into play, there is a large range in the potential coverage of a backpack sprayer. Let me do my best to shed some light on how these variables will affect your total coverage, and how to calibrate your backpack sprayer to know how much area you should be able to spray.
Variables that Affect Backpack Sprayer Coverage
Unlike boom sprayers, backpack sprayers do not have a constant speed or spray pattern. Because you are walking and moving the wand back and forth, the coverage can vary for everyone. But, the two main things that will affect how much area you can cover are application rate and sprayer tank capacity.
The first thing that will obviously play a part in the area a backpack sprayer can cover is the tank capacity. 4 gallons is the most common sized backpack sprayer, but there are many sizes ranging from about 2-6 gallons.
A larger tank capacity allows for more area to be covered. While a smaller tank would cover less area if you are applying the same rate. But, before just choosing the largest tank possible, remember that a larger tank will also be heavier to tote around.
Regardless of the product, you are going to spray, the label on the package should tell you how much to apply to a certain area. This may be ounces per 1000 square feet or gallons per acre depending on the product. The label may also give you a suggested mix ratio or how much product to mix per gallon.
With a boom sprayer, you could mix the correct ratio in your tank, and determine the correct nozzle to apply the needed rate, but with a backpack sprayer, you will need to find out how much water it takes you to cover a certain area before you know how to mix your chemical and water.
Backpack Sprayer vs Boom Sprayer
A boom sprayer provides consistent pressure, speed, and sprayer pattern. This means that your sprayer output is consistent. With a backpack sprayer, it is harder to maintain a constant speed, spray pattern width, and pressure. Changing just one of those things will change your application rate.
It gets even more tricky, considering that the performance of a backpack sprayer will vary with different users. You may spray with a back and forth motion, walking very slowly sideways, while another person may hold their wand steady and walk briskly in a straight line. Then add in the fact that as soon as you pull the trigger, your pressure will decrease. Therefore, the sprayer’s output will decrease. To keep pressure somewhat consistent you must pump the lever at a steady pace.
Small lawn boom sprayers use 12-volt pumps along with a regulating valve that will maintain constant pressure. The speed is obviously easier to maintain with a mower or lawn tractor. This makes calculating sprayer output and coverage much easier.
When you know your nozzle size, speed, spray pattern, and pressure, you can easily calculate your application rate. For more information read this article on calculating your boom sprayer rate and nozzle size.
How to Calibrate Your Backpack Sprayer
How do you know if you are spraying at a rate that will get your target area covered with the correct amount? You need to calibrate your backpack sprayer to find out.
There are some simple ways to go about this. The two main goals of calibration are to figure out how much water you need to cover a certain area and how much of your pesticide/chemical to add to the water.
Calculate How Much Water Will Cover a Given Area
To figure the amount of water it takes you to cover a certain area you will need to do a test run with water only in your sprayer. It is important to remember that there are four factors that will affect your sprayer output and coverage. They are the speed you walk, the nozzle capacity, the swath width, and the pressure at which you spray. If one of these things changes your application rate changes.
One thing you can do to make your rate more precise is to use a battery-powered backpack sprayer like the Chapin 4 Gallon 20V sprayer, to ensure a more even output. I like this one because It uses the same batteries as my Black and Decker drill.
How to calibrate the coverage area of your backpack sprayer:
You will need a few items for this test:
- Tape Measure
- A container that measures ounces. One that holds at least 20 ounces would be best.
- A large concrete or gravel area (A grass area is okay, but it is easier to see where you have sprayed on concrete or gravel)
Steps to calibrate your backpack sprayer:
- Measure a square area of 18.5 x 18.5 feet. This gives you a square 1/128th of an acre, we will explain this later. Mark the corners with flags or just about anything that will clearly mark the corners.
- Fill your backpack sprayer about half full of water.
- Have someone get your timer ready.
- Start the timer and begin to spray the entire square. Start in one corner and spray as evenly as possible. Try to maintain a constant speed and use the same motion with your wand. For best coverage try using a wide-angle spray nozzle so you can just walk and hold the wand steady
- Stop the timer when you are finished.
- Now, point your wand into the container and spray for the same amount of time that it took you to spray your square.
- The amount of ounces in the container, when the timer stops, is the gallon per acre rate that you have sprayed.
This video walks you through this process in more detail:
Alternatively, if you have a set area to spray, you can measure off that area and run a similar test to find out how many gallons of water you used. Then add the chemical amount needed to cover an area of that size based on the guidelines provided on the label.
This video breaks down this method in more detail:
Spot Spraying with a Backpack Sprayer
The example above assumes you want to completely cover the desired area, as you would with a broadcast boom sprayer. But, you may desire to only treat trouble areas in your lawn or only apply chemicals to weeds. This is known as “spot spraying”.
Calculating how much area a backpack sprayer can cover when spot spraying is a bit more challenging. You will not be spraying constantly and you will most likely be applying chemicals more unevenly. Refer to the product label for recommended mixing instructions.
When used this way a backpack sprayer can potentially cover an acre or more of area depending on the prevalence of the weeds or pests in areas you want to treat.
Is a Backpack Sprayer Large Enough for My Lawn?
There are a few things to take into account if you are deciding whether you need a backpack sprayer. We have already talked a bit about the difference between boom sprayers and backpack sprayers, but let’s look at which sprayer would be ideal for different lawn sizes and property types.
A hand pump sprayer is perfect for small lawns and gardens. If you only need to cover 1000-2000 square feet you can get it easily accomplished with a 2-gallon hand pump sprayer. If you have a larger lawn 4000 or more square feet. A hand pump sprayer is adequate if you don’t mind refilling the sprayer a couple of times or if you just intend to spray specific areas and not treat the entire lawn. For example, driveway cracks, landscaped areas, gardens, etc.
Backpack sprayers give you the ability to cover potentially 8-10,000 square feet with one tank full, depending on the chemical you are using. If the idea of needing to refill your hand pump sprayer multiple times is unappealing, a backpack sprayer is probably the right choice. Do remember that a full 4-gallon backpack sprayer will weigh more than 30 pounds. Hauling this around a yard all day may not be an option for you. If this is the case there are wheeled sprayer carts that can give you the benefit of more sprayer capacity without needing to lug the extra weight.
Finally, while a backpack sprayer is perfect for lawns with many obstacles and tight spaces, large open lawns might take some time with just a backpack. If you have an acre or more of open property to treat then a boom sprayer will save lots of time and give you a more precise application.