My4Sons Backpack Sprayer Review

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Written By: Mark Marino

a Massachusetts Core Applicator License holder and owner/operator of Lawn Phix,

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my4sons backpack sprayer ir?t=lawnphix 20&language=en US&l=li3&o=1&a=B01DWCTSQEAfter expanding my old yard an extra 8,000 ft.2– totaling ~17,000 ft.2 I had to ditch the manual backpack sprayer and upgrade to a more suitable battery powered sprayer. I knew I also wanted to make the transition from a granular schedule, to one that included more liquids. For many reasons – particularly cost – liquid applications were the way to go… for the most part.

After spending nearly a full New England season with a $25 backpack sprayer from Harbor Freight, I went all-in on a My4Sons M4 sprayer. I researched other – including King and Chapin – but decided to pull the trigger (literally) on the M4. A bit more expensive than the others, but many factors came into my decision. Here’s what I think of the My4Sons M4 battery powered backpack sprayer.

My4Sons Backpack Sprayer Overview

First off, you will definitely want to watch their quick start videos on their website before you start using your new sprayer. There’s tons of amazing content; everything from the unboxing and new upgrades, to the specifics about nozzles, tips and attachments

Secondly, you won’t receive better customer support from any other backpack sprayer company than Lance and team. I had some questions regarding the backpack sprayer. Lance was very responsive and kind when he answered my questions. And while I am only reviewing my personal experiences with the sprayer, I’ve also heard from several other people that their issues and concerns were quickly fixed by My4Sons. 

They truly want you to be completely happy with your purchase and will ensure your satisfaction.

Updated My4Sons Backpack Sprayer Review

I wanted to update this review after purchasing just under a year ago. After 7 months of use on my cool season lawns, I am glad that I made this investment. The quality of this backpack sprayer is top notch. It’s allowed me to switch to a lot of different liquid fertilizers, soil amendments, fungicides and particularly insecticides

I’m using a lot of Kelp4Less and granular humic acids products and they’ve never clogged once. This has allowed me to feed my turf and soil which has in turn made my lawn the greenest grass on the block (more on the tank below). Liquid fungicides are a far superior option than granular fungicides, so I’ve been able to keep my lawn healthier while saving some money by switching to liquids.

But most of all, I’ve been using my My4Sons backpack sprayer to spray commercial quality insecticides to control and kill mosquitoes and ticks in my yard. The pink fan attachment provides a fine mist. And when the M4 is turned on to full throttle (from 10-60 psi) it acts like a fogger. No more paying $50+ per application from the local pest control companies. 

My4Sons Shoulder Straps

The shoulder straps are triple-thick and extremely comfortable. This is probably my most favorite feature on the M4 sprayer. Even though this unit is on the heavier side – 14 lbs. empty – the over-the-shoulder straps make it feel much lighter. The straps are easily adjustable, too. I’m about 5-foot-9 and carry around more weight than I would like, and this fits with plenty of more room for larger individuals.

There’s both a wand pocket to store the extra wand, and additional pockets to keep the extra tips and nozzles all in one place. This is a big convenience factor for when you need to change nozzles on the fly. 

My4Sons Tank

The My4Sons backpack sprayer is a large 4.5 gallon max capacity tank with clear, large calibrations markings on the outside. Often times it can be hard to measure the total liquid in some backpack sprayers, but My4Sons makes it easy to read.

The large mouth, or opening, makes it easy to fill. Whether you’re using a garden hose or filling the sprayer with a 5 gallon bucket, pouring into this large opening makes things clean and easy. The screw top lid has a wide water-tight seal which is leak-proof. It allows you to shake the backpack sprayer and even tipping it upside down without spilling or leaking.

There is a basket filter that sits on top of the inside of the tank. This can be accessed and removed easily. I like this feature a lot since some of my dry humic acid doesn’t 100% dissolve. This basket catches the large granular pieces before making its way into the tank.

There is also fine filter in the bottom of the tank which is a friction-fit. This helps catch any debris before going into the pump and is easy to remove and clean. This is a great feature to provide extra filtration so nothing gets clogged. With both filters clean and in tact, I’ve never experienced any clogging with any of the Kelp4Less products.

My4Sons Nozzles

My4Sons provides plenty of nozzles and tips with the M4S backpack sprayer. Everything a flat fan pattern to a fine mist to a sharp linear stream, there’s a tip for all of your spraying needs. Here’s a list of some of the tips that come with the M4. Note: the brass tips

  • Flex tip (flexy) – fan spray to a linear stream
  • Plastic T-Jet
  • Plastic Single Cone
  • Plastic Double Cone
  • Pink Fan (Fine mist – I use this for spraying insecticides, like a fogger)
  • Black plastic tips can go onto the brass HD wand, the black plastic wand, or screw onto the flexy
  • Brass T-Jet (flat fan)
  • Brass Double Cone
  • Valve O-Ring Piston (red, extra piece)

After owning this backpack sprayer for about a year now, the flexy is now leaking a bit. But I, and others who have borrowed it from me, have used this tip a lot. A replacement is only $3.99 on their website so I’m not too concerned about replacing this. 


My4Sons Wands & Hoses

The My4Sons backpack sprayer has an extremely strong, durable and flexible Viton hose. It’s 48″ in length and reinforced with high pressure PVC. It easily snaps and connects to the smaller hose which screws into the sprayer.

The valve handle, which screws into the end of the 48″ hose, has a lock switch which allows you to keep a consistent spray without physically gripping the trigger. There’s also a screw to release pressure should you choose, and where you can replace the valve o-ring piston if needed.  

The My4Sons M4 backpack sprayer comes with a black plastic wand and an adjustable brass HD wand. The brass wand has good extension and makes for comfort when walking and spraying large areas. I had no issues with leaks either one. For everyday fertilization, the brass HD wand one is recommended. The black plastic wand is recommended for bleach and acids. 

Due to my own fault, the trigger lock on the valve handle broke. It still sprays without leaking or issues, but just won’t lock “ON”. A replacement handle is just $4.99, so getting a backup didn’t break the bank.

My4Sons Battery

The M4S backpack sprayer has a heavy battery but is easy to slide in/out. The rechargeable lead acid battery provides many hours of max spraying on a single charge. Although I have a smaller yard (8,000 sq. ft.) my last charge was back in April (today being June 26, 2020).

The charger for the M4S battery is very convenient. There’s an indicator light that turns from red (changing) to green when it’s fully charged. 

There is a volt meter on the front of the M4S backpack sprayer. This indicates the level of remaining power in the battery. A red and green light means the battery is good and charged, which takes the guess work out of it. 

My4Sons Spraying

The My4Sons M4 model has a main on/off switch (red), and a silver rotary dial to adjust the psi (from 10 – 60 psi). This backpack sprayer is a parallel unit, which means it is wired to allow both switches to turn the unit ON.

The main on/off switch on the My4Sons backpack sprayer turns the unit on to the max (60 psi). To operate the silver rotary psi variable flow switch, the main red on/off switch must be OFF. Otherwise the red switch turned ON keeps power at 100%.

I like the variable pressure. If I’m in a rush and need spray fast, I turn it on 100% and walk briskly. Full 60 psi with a sharp stream from the flexy is almost like a mini power washer – very powerful! You can even feel a little kickback when squeezing the trigger.

When you need a  more gentle stream or shower for flowers and herbs, you simple turn the switch off, and turn the rotary dial to your desired pressure.  

My4Sons Backpack Sprayer Verdict: 95/100

I absolutely love this backpack sprayer. Aside from my own irresponsibilities in missing and breaking some pieces, the My4Sons has been a rock. I have friends, family and even neighbors borrowing it and they all say the same thing – they are blown away by the comfort and power of this sprayer.

I’m glad I purchased the M4. If something were to happen to it, I would immediately buy another one without researching an alternative. You can get your very own M4 on Amazon.



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Author's Note: this piece has been updated for accuracy since its first publication on
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Author: Mark Marino
My name is Mark Marino, and I am the founder, owner, and operator of Lawn Phix. With a passion for lawn care and turf nutrition for over a decade, I've dedicated countless hours to correcting soil and perfecting lawns. Today, my expertise, backed by formal courses at UMass Extension Pesticide Education, allows me to offer top-tier lawn care services and advice. I am a fully licensed and insured lawn care applicator in Massachusetts, specializing in comprehensive turf nutrition, weed control, and lawn pest control. My license number is AL-0053865. Contact me at [email protected] or +1 (508) 500-8402.

4 thoughts on “My4Sons Backpack Sprayer Review”

  1. Hi Mark,

    I also have this backpack sprayer have you made any modifications to the sprayer at all? I plan on adding a pressure gage on the hose close to the wand, I plan on buying tee jet nozzles for different applications. Which stock nozzles are you using for fertilizer spraying and herbicide sprayer.

    I guess I should have started by saying I just recently found this blog and find the info interesting and informative. Its helpful for my quest in really diving deep in taking care of my lawn and landscape plants which just started this year. Throwing out NPK in the yard to grow thingsisnt the end all, there are other important amendments to add like sea kelp, humic acid etc that i just started learning about.

    Keep up the good work, and look forward in reading your next blog post


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