Knapsack-Sprayer

5 Best Knapsack Sprayers to Keep Weeds at Bay (2021 Review)

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Whether you’re looking to fertilise your plants or kill unwanted weeds, the best knapsack sprayers should be comfortable to wear and easy to use.

With capacities ranging from 5 litres all the way up to 16 litres, it’s also important to choose the right size for your garden.

We’ve researched and tested the best models analysing everything from the shoulder strap to the nozzle. Here’s what we recommend based on our findings…

What is the Best Knapsack Sprayer?

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Comparing The Best Knapsack Sprayers

Use the dropdown to sort the table by the feature that's most important to you.

  • Best For
  • Capacity
  • Weight
  • Shoulder Strap
  • No. of Nozzles
  • Cost
  • Our score
  •  

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In-Depth Reviews of Our Recommended Knapsack Sprayers

Spear & Jackson Pump Action Pressure Sprayer 5 LitreSpear & Jackson Pump Action Pressure Sprayer 5 Litre

Best knapsack sprayer overall

Design
Ease of Use
Comfort
Value for Money
Overall
4.525
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Spear & Jackson Pump Action Pressure Sprayer 5 Litre Review

Specifications

  • Capacity: 5 L
  • Weight: 0.4 kg
  • Shoulder Strap: Yes
  • No. of Nozzles: 1

Within this list there are some pricier sprayers, but it doesn’t always make sense to spend a lot of money if a cheaper option is all you need. As always, it depends what job you’re doing, but the Spear & Jackson Pump Action Pressure Sprayer is a small, basic knapsack sprayer that will help apply herbicide, pesticide, water, or other liquids to the garden.

It’s a budget option, that’s true, but Spear & Jackson make some quality tools, and this is no different. The primary features work well, and the secondary areas are where costs have been kept down.

For example, the spray that is produced from the lance is powerful enough without being overly pressurised, and turning the nozzle gives a range of different sprays – whether you want to mist the humidity-loving plants in your garden, or apply cleaning solution to your patio. Therefore, in terms of primary function, it works well.

With just a 5 L capacity, it’s one of the smallest sprayers here, and may not be the best knapsack sprayer for larger gardens; however, its small size does help to keep the weight down.

This is perhaps just as well, as its biggest shortcoming is the strap provided – it comes with a shoulder strap, instead of the backpack-style arrangement of the other knapsack sprayers, which is generally less comfortable. The tank can swing around, bumping your leg whilst in use.

That said, every cloud has a silver lining: in this case, the fact the sprayer is positioned at your side means you can pump it when necessary, in order to continue spraying, without having to take off the unit.

Overall, this isn’t a sprayer that can be used for jobs that require high pressure; it doesn’t produce a jet that will clean a car, for example; however, for applying solutions over plants, or cleaning products to surfaces before giving them a scrub, it’s a good tool to have around.

Pros

  • Container has a very solid build - all liquid is safely contained
  • Simple to use with an air valve to release the pressure if needed
  • The trigger can be locked for continuous spraying
  • Needs just a few pumps every few minutes to maintain pressure

Cons

  • The included lance may be too short for tall users
  • The lance is made from plastic as opposed to metal so it's not quite as durable
  • The spray nozzle can be a little stiff to adjust
  • Plastic container can degrade if left in sunlight - best stored in the dark
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VOXON 5 Litre Pump Action Garden Knapsack SprayerVOXON 5 Litre Pump Action Garden Knapsack Sprayer

Best budget knapsack sprayer

Design
Ease of Use
Comfort
Value for Money
Overall
4.575
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VOXON 5 Litre Pump Action Garden Knapsack Sprayer Review

Specifications

  • Capacity: 5 L
  • Weight: 0.84 kg
  • Shoulder Strap: Yes
  • No. of Nozzles: 1

For smaller gardens, the VOXON 5 Litre Pump Action Garden Knapsack Sprayer has a good spray without requiring you to carry around a large, heavy tank.

Weighing under 1 kg when empty, when filled with water it doesn’t exceed 6 kg. If you’re concerned about carrying heavier weights, or just want something that’s less effort, it’s a design that’s suitable for the majority of gardeners.

It’s easy to pick up, and, once supported on the back with the backpack-style straps, it becomes very manageable.

Due to its size, it’s obviously best suited to small/medium gardens, but if you don’t want anything heavier you could also use it over larger spaces too – you’d just have to spend more time filling it so jobs would take longer.

Fortunately, VOXON have made the container translucent, which at least means that time can be saved when mixing and diluting chemicals; this can be done directly into the container, using the level markings as a guide.

There’s also a built-in funnel as part of the design, which avoids spilling water or chemicals over the side when filling – something that can happen with other sprayers. Not only does this reduce waste, it stops nearby plants and paving coming into contact with chemicals by accident.

As a cheaper, smaller model, it doesn’t hold pressure quite as well as some more expensive knapsack sprayers, so you’ll likely find that you need to take it off and pump it more often than you would with those models – especially if you want to maintain a powerful spray. Fortunately, it isn’t too difficult to take the sprayer off to do this, as it isn’t heavy to pick up again, but it does slow down some tasks.

Pros

  • A great lightweight option for smaller gardens
  • Arrives pre-assembled so ready to use straight away
  • A full replacement set of silicon rubber seals and o-rings are supplied
  • A permanent funnel attached to the top prevents wastage
  • Level markings on the outside ensure perfect ratios each time

Cons

  • It can be tricky to get the nozzle setting just right - with a very small difference between the fine mist and full needle
  • The clip for storing the wand is fiddly
  • The lance is quite short so may not be comfortable for taller users
  • The spray function pressure is a little disappointing
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Hozelock Pressure Sprayer Plus 7 LitreHozelock Pressure Sprayer Plus 7 Litre

Best mid-sized knapsack sprayer

Design
Ease of Use
Comfort
Value for Money
Overall
4.475
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Hozelock Pressure Sprayer Plus 7 Litre Review

Specifications

  • Capacity: 7 L
  • Weight: 1.77 kg
  • Shoulder Strap: Yes
  • No. of Nozzles: 1

Whether using a hose, lawnmower or pressure sprayer, having to keep the ‘on’ lever held down for extended periods is no joke – hand fatigue doesn’t take long to set in.

If this is something you’re all too aware of, one of the best things about the Hozelock 7 Litre Pressure Sprayer is that the flow can be locked ‘on’ to enable continuous spraying

Whilst some pressure sprayers require you to constantly squeeze the spray trigger, this model gives your hands a bit of a rest making it a lot easier to use for longer jobs.

Of course, this ‘continuous use’ is limited to how long it takes before the tank needs refilling, but generally you can get at least 20 minutes from the 7 L container – this would certainly feel like a lifetime if you were holding the lever down the whole time.

There are other pressure sprayer that seem to constantly leak air and reduce in pressure, but this Hozelock model stays pretty true to what you expect – 23 pumps can give 20 minutes spray time without requiring much (if any) additional pumping in between.

Made of thick plastic, it feels durable which is reassuring when potentially using chemicals like weed killers and pesticides. The container is also translucent, with measuring marks, so you can very easily dilute solutions and see how much liquid is left.

Weighing 1.77 kg when empty, the sprayer itself doesn’t add on too much weight, and there is a shoulder strap included as well – just another factor that helps it be easier to use for extended periods. This isn’t the most comfortable strap in the world, with no padding, but it does help distribute the weight and keep the sprayer secure, at least.

The spray itself is also very impressive – when used with the maximum 23 pumps, it’s powerful enough to wash windows and cars, with the strength of a standard pressure washer. You therefore need to get used to its power, and work out how many pumps best suit each job, to avoid jet washing the lawn when you’re trying to apply weed killer.

Pros

  • Very simple to fill, empty and clean
  • The hose can be locked so that it sprays continuously which allows you to work with minimal fatigue
  • The spray pattern is simple to adjust and very effective
  • All fittings and seals are solid and secure

Cons

  • The lance supplied is a little short for targeting individual weeds without stooping down - taller users may need to purchase an extension lance
  • The spray isn’t particularly powerful so best suited to lighter tasks
  • Not easy to assemble, especially if you’ve never used a knapsack sprayer before
  • Shoulder strap is secure and safe, but not very comfortable
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Faithfull 16 Litre Knapsack SprayerFaithfull 16 Litre Knapsack Sprayer

Best for large capacity

Design
Ease of Use
Comfort
Value for Money
Overall
4.35
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Faithfull 16 Litre Knapsack Sprayer Review

Specifications

  • Capacity: 16 L
  • Weight: 1.84 kg
  • Shoulder Strap: Yes
  • No. of Nozzles: 4

Working in a big garden can be seriously slowed down by using the wrong-size tools. If you don’t want to keep stopping, the Faithfull 16 Litre Knapsack Sprayer is one of the best knapsack sprayers for use in larger spaces. With a 16 L capacity, it’s quite a lot larger than other models featured here.

Of course, with this sizeable capacity come some polarizing pros and cons: if you can manage the weight of the full sprayer, which can be mounted on your back with the backpack-style straps, it can really save time; however, if it’s too heavy, jobs are going to take longer.

That said, it doesn’t have to be used to full capacity, so you could predominantly use it part-empty, and just have the option to fill it full when necessary.

Due to its large size, it also needs to be frequently pumped to create pressure – it’s not possible just to pump at the start of the job and be away. Fortunately, this pumping can be done whilst wearing the sprayer, using one hand on the ergonomic side lever whilst the other hand holds the nozzle.

Several nozzles come included, as well a lance, which offer a range of spray options. These can be used to efficiently spray weeds, flowerbeds, car hub-caps, or anything else you choose, and the lance is a comfortable length to reduce stooping and protect the ol’ back from strain.

The components are all made from tough plastic and are shatter- and frost-resistant; something that is good to know when working out where to store tools over winter.

One further thing to note: whilst the extra nozzles come in handy, they need to be extremely well cleaned to avoid blockages – it seems the small openings catch debris easily.

Pros

  • There is very little dripping from the nozzle once the trigger is released so your other plants will be safe from weed killer
  • Gives a quick and even coverage using both the single head and fan head
  • The mouth is large so filling to capacity doesn't take long
  • Additional nozzles included make it suitable for a range of outdoor tasks

Cons

  • When filled to capacity, this 16L sprayer is very heavy. Smaller users may struggle to put it on without an extra pair of hands
  • The nozzles need meticulous cleaning to prevent blockages
  • While the straps are sturdy, they will dig into your shoulders if you aren’t wearing many layers
  • Unless all screws are very well tightened, this knapsack sprayer will leak
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Matabi Supergreen 12 Litre Knapsack SprayerMatabi Supergreen 12 Litre Knapsack Sprayer

Best lance

Design
Ease of Use
Comfort
Value for Money
Overall
4.35
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Matabi Supergreen 12 Litre Knapsack Sprayer Review

Specifications

  • Capacity: 12 L
  • Weight: 3.16 kg
  • Shoulder Strap: Yes
  • No. of Nozzles: 4

Being able to control the pressure on a knapsack sprayer can be difficult – often, there’s no way to regulate the output once it’s been ‘pumped’. This isn’t the case with the Matabi Supergreen Knapsack Sprayer though, which has a pressure regulator on the lance.

You can choose between an output of either 1.5 bars or 3 bars by turning a valve. This is especially useful for spraying different products; for example, on 1.5 bars the droplets are bigger, which is better for spraying herbicide as they don’t catch in the wind and get on other plants. Using the 3-bars setting creates finer droplets, ideal for pesticides (or general light-misting jobs).

If the pressure drops below the desired setting, the sprayer will cut out until it’s pumped again, which is much better for ensuring correct droplet size throughout the whole time.

There are also different nozzles included, which help control the power and shape of the spray further, and the lance is a good length to be used without stooping.

This is the sprayer with the second-largest capacity featured here, able to hold up to 12 L, and it weighs just 3.16 kg when empty. When filled, it weighs somewhere around 15 kg, but the straps work to distribute the weight evenly over your back. It’s a good size if you’ve got a larger garden, even if it’s not the most comfortable to wear for an extended period.

Unfortunately, you can’t see inside the container which means it isn’t possible to know exactly how much liquid is left, nor is it possible to accurately dilute chemicals directly inside the sprayer – this has to be done separately which is a bit more time consuming.

Pros

  • Sufficiently comfortable to use even when filled to capacity
  • The included lance is telescopic so it’s suitable for any height user
  • Spare parts are easy to find
  • Won’t leak which makes it suitable for weed killer

Cons

  • Meticulous cleaning is needed after every use to prolong its lifespan
  • The carry straps are awkward to fit initially
  • Not transparent so you won’t be able to see how much product you’ve put in it
  • Assembly instructions aren’t easy to follow
  • Can be adjusted for both right- and left-handed users
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Things to Know Before Buying a Knapsack Sprayer

Anyone with a large garden will know how much of a full-time job it can be to effectively eliminate weeds and pests.

Hauling bottles and buckets of weed killer around with you is exhausting, and if your weed killer spills onto your plants, it may kill them too!

Introducing a knapsack sprayer into your life for these jobs will be a real game-changer – you can safely carry your weed killer or fertiliser around with you and the weight will be comfortably distributed across your back.

If you’re considering purchasing a knapsack sprayer but not sure what to look for, take a look at these top tips:

Material and Durability

It’s essential that your knapsack sprayer is made from thick materials that won’t corrode when exposed to harsh chemicals.

Most knapsack sprayers are made from sturdy, hard-wearing plastic, and you should ensure that the hose, lance, fittings and seals are all made of good quality materials too.

No matter the quality of your knapsack sprayer, it won’t last as long if you don’t wash it out well between uses. If you’re using any chemicals, such as weed killers, make sure that none of the solution is left in the tank after use – it could corrode the plastic over time.

If you plan on using your sprayer for a few years, it’s good practise to check that you can easily replace broken parts. Ultimately, this will save you money in the long run.

Keeping the sprayer out of direct sunlight will also help extend its life – plastic will degrade quicker when exposed to UV, so it’s best to store it away as much as possible.

Choosing the Right Capacity

The size of the sprayer you need will depend on what you hope to use it for.

Generally, a 5 L tank will be best for small areas. So, smaller gardens, patios, and standard driveways. A 5 L tank will also mean a lighter unit when full, which might be more suitable if you aren’t able to support heavy weight for a long period of time.

Of course, with a smaller tank capacity you will have to fill it more often if you plan to do larger jobs.

For large driveways or gardens that need a lot of care and maintenance, a larger tank will save you time as it won’t need refilling as frequently. Keep in mind that a larger tank will add a considerable amount of weight to the unit when full.

A 12 L knapsack sprayer can weigh in the region of 15 kg when full of water (given that the unit itself also weighs something to begin with).

Choosing the right capacity ultimately comes down to how large the area you want to treat is, and how much weight you can comfortably support.

In terms of task-completion time, you may find it more effective (and safer!) to have a smaller unit which you can move around with more easily, rather than a larger one.

Look for Adjustability and Comfort

Following on from the subject of sprayer weight, you’ll find it far easier to carry a full knapsack sprayer if it’s comfortable.

Backpack-style straps are generally more comfortable than shoulder straps, especially if you’re going to be using the unit for a long period of time.

If the sprayer has adjustable and/or padded straps it shouldn’t dig in as much – especially important with units that have a higher capacity. An ergonomic pump handle and trigger will also reduce the strain on your hands.

Look for a trigger that can be locked in an ‘on’ position. This will mean you won’t have to constantly apply pressure to create a continuous flow. It will therefore prevent aching hands and blisters.

Length of Lance and Hose

Finally, take a look at the length of the lance and hose.

A hose that’s too short will mean you are stooping continuously whilst working. This will cause pain and may also slow tasks down because you’ll have to constantly stop and stretch.

Make a note of the lance length in the product description and measure this against yourself. If you have to bend so that this measurement reaches from the floor to your hand, the lance may not be long enough for you.

The nozzle should also be adjustable so that you can choose the right setting for your requirements – at the very least you’ll want a jet option and a spray option for different jobs.

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Knapsack Sprayer FAQs

How can I make my knapsack sprayer last as long as possible?

To ensure you get the best out of your sprayer you should clean it thoroughly after every use. This will remove potentially corrosive chemicals from the tank, hose and lance.

You can buy special pump cleaners, alternatively or flush the unit through with clean water. In addition, you should store your unit in a dry, frost free location.

Lubricating the joints and seals can keep them from drying out and cracking. Always remember to check for leaks before filling your sprayer with chemicals.

When is the best time to use my sprayer?

It is best to spray weeds on a dry day when no rain is forecast. Rain can wash the weed killer away before it has a chance to work. You should also choose a day that is not windy to avoid the weed killer being blown onto adjacent areas and damaging other plants.

Can I use the same sprayer for weed killers and pesticides?

It is not recommended that you use the same sprayer for both pesticides and weed killers. This is because, even with thorough cleaning, your sprayer may contain traces of weed killer. This could harm your plants if applied to them alongside pesticide. To be on the safe side, keep a specific sprayer for weed killer and don’t use it for anything else.

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