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Published Nov. 15, 2021

When traveling through the backcountry, water is life, and knowing where to find water and how to purify or filter water are essential wilderness skills. At 8.34 pounds per gallon, water is also one of the heaviest things to strap on your back, so being able to replenish water along the way lightens your load and extends how far you can travel. In an emergency or survival situation, being able to access safe water could mean the difference between life and death, as humans can go about three weeks without food but only three days without water. Water is life, and you never want to be caught without it.

There are a lot of portable water filters and purifiers on the market, so we reviewed the best backpacking water filters out of all of them to help you make the purchase that’s right for you. Shop smart and stay hydrated — or else.

We loved the Platypus GravityWorks when we reviewed it in detail earlier this year. While this high-volume filter is a top performer, it’s overkill for solo use and ideal for groups of two or more. For smaller groups, we recommend the 4L version, although Platypus also offers a 6L version for larger groups. The Platypus GravityWorks is a lightweight system at 11.57 ounces (328 grams) and filters quickly, working through up to 1.75 liters per minute depending on how much sediment is in the water. Once set with the dirty bag placed above the clean bag, gravity does the work, with no laborious pumping required. The system is versatile enough so that the clean bag can be used in a backpack as a hydration bladder or hung from a tree for camp use. It’s also compact and, when rolled up, takes up about the same space as a Nalgene 1L bottle. The filter is replaceable (manufacturer recommends after 1,500 liters of use). Most importantly, the hollow fiber technology filters out any particles larger than 0.2 microns which removes 99.9999 percent of bacteria and 99.9 percent of protozoa. We’ve filtered some pretty turbid water with the GravityWorks over the years, and it has performed every time.

Product Specs
  • Filtration performance: Filters to 0.2 microns
  • Speed: Up to 1.75 liters per minute
  • Weight: 11.57 ounces (328 grams)
PROS

Fill-and-forget filtration, gravity does the work

Fast at up to 1.75 liters per minute

High capacity at 8 or 12 liters depending on model

Effective to 0.2 microns

Made from thick, soft, flexible BPA-free plastics

Versatile as a hydration bladder, group water source, or shower

Produces great-tasting clean water

CONS

Filter prone to clogging, requires frequent backflushing

Filter must be protected from impact and freezing

Ziplock at top of dirty bag is prone to clogging

Does not filter out viruses, heavy metals, or chemicals

Expensive

Of all the water filtration products we tested, the Katadyn BeFree was one of the very lightest in the built-for-personal-use category. Weighing in at 2 ¼ ounces (64 grams), this personal drink-through-the-filter system provides on-the-fly hydration. One simply unscrews the reservoir bag from the filter lid, fills the reservoir with water from a spring or creek, re-attaches the filter lid, and squeezes away. The reservoir bag is soft to the touch (as opposed to Platypus reservoirs), and I was initially concerned about breaking the bag by squeezing it, and other internet reviews we researched listed similar durability concerns. These concerns were unfounded as it withstood our tests. This hollow fiber filter removes bacteria and protozoa but not viruses. The filter itself is fairly durable and good for 1,000 liters of use. We tested the filter with the 1L bag, but Katadyn also makes 0.6 and 2L variants.

Product Specs
  • Filtration performance: Filters to 0.1 microns
  • Speed: Up to 2.6 liters per minute
  • Weight: 2 ¼ ounces (64 grams)
PROS

Among the very lightest of the lot

Super fast flow rate

All-in-one system

Easy to backflush, no additional equipment needed

Super easy to use, wide mouth

Collapsable/stowable

Better in cold conditions than other filters

CONS

Soft bag makes us concerned about long-term durability

Filter only compatible with other Katadyn bags

High filter cost for 1,000 liter use life

Struggles with high sediment water

Best Personal Use

The Sawyer Squeeze drink-through system has been a longtime favorite of long distance hikers on the Appalachian Trail, although we’ve seen most users ditch the water bags that the Sawyer filter comes with in favor of 1 or 1.5L SmartWater bottles available at most convenience stores. Many have complained about the long-term durability of the water bags. This is a filter designed for long-term reliability and is ideal for hiking, backpacking, camping, hunting, fishing, emergency preparedness, or travel to places abroad with sketchy tap water. The Sawyer Squeeze is rated to 0.1 microns and removes 99.99999 percent of all bacteria, 99.999 percent of all protozoa, and 100 percent of all microplastics. It’s also easy to use: You fill the reusable water pouch, screw on the filter, and drink directly from the clean end of the filter or squeeze the water into another drinking container or cooking pot. The kit comes with two 32-ounce water pouches which are BPA-free.

Product Specs
  • Filtration performance: Filters to 0.1 microns
  • Speed: Up to 1.5 liters per minute
  • Weight: 2.5 ounces (70 grams) [filter only]; 6 ⅝ ounces (188 grams) [full kit]
PROS

Fastest filter rate of all tested

Lightweight at 6.5 ounces

Compact

Low cost

Filter unit is compatible with other 28mm standard water bottle threads

Filter good for 1,000,000 liters of use

CONS

Squeeze bags not clear, hard to see when they need to be cleaned

Squeeze bags have durability challenges

Must be protected from impact, freezing, durability issues

Needs frequent backflushing, requires additional equipment

Not good for groups

Best Virus-Killing System

It’s important to note that most portable water filtration systems don’t remove viruses. This may be especially important when traveling outside of the United States to places with sketchy water supply systems. The World Health Organization estimates that nearly 25 percent of the world’s population is consuming fecally-contaminated water. Adenovirus, astrovirus, hepatitis A and E, rotavirus, norovirus and their ilk can turn a vacation into a disaster.

The good news is that there’s a technological solution available: UV light. The WAATR CrazyCap uses a LED UV light emitter built into the canteen’s cap to sterilize tap water in one minute, and water from springs and other wild sources in two and a half minutes. It is also self-cleaning in that it turns on every four hours for 20 seconds to keep the bottle free of mold, bacteria, viruses, and other harmful pathogens.

It’s important to note that this device does not filter water, so be careful to fill it with water that is free of debris or other particulates. The UV-emitting cap is rechargeable in four hours or less with a USB compatible charger. A single charge lasts about one week. Safety note: Do not irradiate eyes.

Product Specs
  • Filtration performance: Destroys viruses, bacteria, and protozoa
  • Speed: Up to 1/4 liter per minute (requires 2 min cycle for 17 ounces)
  • Weight: 12.6 ounces (357 grams)
PROS

Kills viruses, bacteria, and protozoa

Super easy to use

Rechargable, long battery life

Rugged stainless steel

Insulated

CONS

Low storage capacity at 17 ounces, not good for groups

Does not filter out particulates, heavy metals, or chemicals

Not collapsable

Needs electrical source to recharge

Needs fairly clear (not turbid) water to be effective

Expensive

Lightest Water Filter

If shedding every possible extra ounce is your thing, the 1 ⅝-ounce LifeStraw just might be your device. I’m usually that guy, but wasn’t satisfied with the practicality of the LifeStraw for day-to-day trail use. The LifeStraw was designed to provide excellent filtration at a reasonable price, and on that, it delivers. What I found less than appealing was laying on the ground next to a muddy creek bed to drink from the source. Even with a dedicated, dirty-water 1L Nalgene bottle, I still had to unscrew the lid, fill the bottle, and then go through a seven-step process of opening the LifeStraw’s top and bottom caps, sticking it inside, drinking, removing it, blowing out the excess water, closing the caps and then closing the bottle. This makes using it while walking very difficult. With that said, it is an ideal device for a survival kit or backup to your main filtration device should it crap the bed on a long trip.

Product Specs
  • Filtration performance: Filters to 0.2 microns
  • Speed: It varies; I was able to achieve 1L per minute
  • Weight: 1 ⅝ ounces (48 grams)
PROS

Super lightweight

Removes 99.999% of protozoa and 99.999999% of bacteria

Decent life, 4,000 liters or 1,000 gallons

No moving parts

Easy-to-use design

Cheap

CONS

No storage capacity

Must be protected from impact and freezing

Does not remove viruses

Must suck by mouth to use

Best for International Travel

The Grayl Geopress stands out among water filters in that it removes not just protozoa and bacteria, but viruses as well, a rarity among filter systems. It also removes many heavy metals and chemical contaminants. This is especially useful in areas with polluted water sources. The system works like a French press — you simply put dirty water in the exterior container, insert the filter container, and plunge. It takes some time and effort to depress. The manufacturer claims a 1L per eight-second flow rate, but the fastest I could fully deploy the plunger was 32 seconds, and this was with tap water. I strongly recommend prefiltering water with a lot of sediment/turbidity. While the system is ruggedly built, it is one of the heavier and less-packable options (doesn’t compress like soft bags). It will survive drops up to 10 feet. The activated carbon-ion exchange technology in the filter delivers great-tasting water. The filter also has a short use life of 65 gallons (250L). Also, you must protect this filter from freezing.

Product Specs
  • Filtration performance: Removes bacteria, protozoa, viruses, particulates, chemicals, and heavy metals through activated carbon and ion exchange technology
  • Speed: Manufacturer states 5 liters per minute; I was only able to achieve 1.33 ounces per minute
  • Weight: 17 ounces (482 grams)
PROS

Removes 99.99% of viruses, 99.9999% of bacteria, and 99.9% of protozoa

Also filters particulates, chemicals, and heavy metals

Great taste, no smell

Independently certified to NSF/ANSI standards

Easy to use

Rugged

CONS

Heavy

Bulky, not compressible

Short filter life of 65 gallons (250L)

Takes longer to press than manufacturer states

Struggles with high-sediment water

Why you should trust us

The active-duty and veteran gear reviewers here at Task & Purpose test the products we review at home and in the field. We have years of experience living and working outdoors with the tools we recommend. We don’t get paid by the manufacturers and we have editorial independence. Our editor leaves it to us to recommend, and prints what we write. All of this enables us to provide you, our valued readers, our unvarnished, honest opinions on the recommendations we make.

Types of backpacking water filters

The main difference between water purifiers and filters is the size of the microorganisms they remove. Portable water purification systems generally use boiling methods, chemicals like chlorine or iodine, or UV light to kill pathogenic organisms to include protozoa, bacteria, and viruses. Most purification systems do not filter out suspended solids in the water, so it will turn out clean but occasionally “chunky.” Chemical drops tend to be low-cost options, but not the most effective against some seriously gnarly bacteria. Water filters work by passing dirty water through a filter media to strain out protozoa and bacteria, but do not generally remove viruses. Water from these systems is free of sediment and solids but may contain viruses, so you need to be careful as to where you source your water. These options are more expensive than chemical drops since equipment is required. 

Almost all of the backpacking water filters reviewed here meet or exceed EPA water filtration standards. Most filter to 0.1 microns which gets rid of most protozoa and bacteria (but not viruses). Whatever system you choose, we strongly recommend you read this CDC Guide to Drinking Water Treatment and Sanitation for Backcountry & Travel Use.

Boiling water

This is the cheapest and one of the most effective backcountry water purification techniques. Simply fill a pot with water, set it to a rolling boil for at least one minute (per the World Health Organization and Environmental Protection Agency), and then pour the water through a clean bandanna or paper coffee filter into a canteen. The pros are that it’s cheap and is sufficient to kill pathogenic bacteria, protozoa, and viruses. The cons are that it takes a stove, fuel, paper, or cloth filter medium, and lots of time. It also sucks to drink hot water on warm days.

Chemical purifiers

Using iodine or chlorine drops to kill waterborne pathogens is a fairly cheap and straightforward process. One simply adds the requisite dose of chemical purifier to a canteen of water and waits a specified period of time, generally 30 minutes to four hours. The pros of this method is that it is low-cost. The cons are many, as the water usually tastes like chlorine or iodine, is frequently “chunky” since there is no filtration system involved, and you might still get the shits. While chlorine has a low to moderate effectiveness in killing Giardia, it tends to have high effectiveness in killing bacteria and viruses. Neither iodine nor chlorine is effective in killing Cryptosporidium. We recommend using these methods as a backup to main backpacking water filter systems. 

Ultraviolet light purifiers

Several manufacturers like WAATR and SteriPen make water purification systems that use ultraviolet light to destroy pathogens to include viruses. Turbid water degrades their effectiveness as harmful microorganisms can hide from the light behind particles in the water. Generally, these systems aren’t great for processing large amounts of water at one time. These systems require batteries or electrical charging, so they are less than ideal for long trips. 

Pump filtration systems

These systems are old-school and most backpackers do not use them anymore. One of the advantages is that they typically have siphon hoses which allows for easier access to very shallow water sources, and a rare few remove viruses. The cons are that pumping is a pain in the ass, they tend to be more expensive, and they’re bulky, slow, and heavy. They’re also hard to clean in the field. For this reason, we don’t recommend them for backpacking in most instances.

Hollow fiber filtration systems

Most modern backpacking water filtration systems use some form of a hollow fiber filter tube encased in filter cartridges. These systems work by essentially straining out particles larger than a few microns to include most pathogenic protozoa and bacteria. Almost all do not filter out viruses. Some of these systems rely on you to squeeze a bag containing the water to be filtered through the filter canister, and others are designed so you can simply place or hang the dirty bag above the canister and allow gravity to do the work for you. These filter cartridge systems almost always require backflushing as the filters become clogged with silt, sediment, and other suspended solids. Some, like the Katadyn BeFree, are all-in-one units combining the filter and the reservoir. Others are separate units like the Platypus GravityWorks system.

Key features of backpacking water filters

Performance

Look for filtration systems that filter out particles larger than 0.1 microns and will remove 99.9999 percent of bacteria and protozoa. If viruses are a concern, consider boiling, chemical, or UV purification methods. 

Lightweight

When backpacking, you have to carry everything you need on your back. Weight matters: The lighter the load, the farther and faster you’ll travel, and you’ll have a more enjoyable time doing it. You can find many good water filtration systems that weigh less than a pound. Go for the lightest that adequately meets your needs. 

Capacity

It’s important to know whether you’ll be using the filtration device just for your own needs or for a group. For yourself, you can get away with a low-capacity device. For groups, multiple people relying on a limited capacity system is a recipe for frustration, which is always amplified when you are tired and thirsty. Most of the filtration systems listed here will produce several liters of water in just a few minutes. If it’s just you, go with the Sawyer Squeeze or Katadyn BeFree. If it’s you plus others, go for the Platypus GravityWorks or the 2L variant of the BeFree. 

Speed

Speed of filtration is a concern when you’re on the go. Every break taken to filter water on the trail equates to distance not walked. I prefer the Platypus system, so I tend to plan breaks around water sources so I can rest my body while filtering water. For on-demand, on-the-fly filtration, go with the Sawyer Squeeze or Katadyn BeFree. Strive to be efficient in the backcountry. Wasted energy equals more fatigue. Look for systems that don’t take a long time to produce clean water. 

Benefits of backpacking water filters

Health and hydration

When in the backcountry, it’s imperative to minimize risk as you are usually hours if not days from help. Dehydration and heat-related illnesses can lead to disastrous consequences if not anticipated or quickly addressed. The human body can survive for weeks without food, but only days without water, and staying hydrated with clean, safe water is critical in maintaining peak performance. 

Packability

Like weight, packability is a major consideration when selecting backpacking equipment like water filtration systems. I prefer to take the least amount of gear that provides me the greatest amount of utility and safety margin. When everything takes up cubic inches in a backpack, I lean in the direction of small, collapsible, and stackable. When deciding between two equally performing systems, choose the smaller and lighter one. All of the filtration systems we reviewed are lightweight and easily stowed in a backpack — and some are smaller, much smaller than others.

Ease of use

Even a Marine could operate the most complicated system we reviewed. Ease of use is critical. When traveling far from home in areas with limited resources, simplicity reigns. Typically, the fewer the number of process steps or moving parts, the simpler the system. The best-designed water filtration equipment is that which you can operate when fatigued, in the dark, or in an emergency where time is of the essence. Just like your drill instructor told ya, K.I.S.S.: Keep it simple, stupid!  

Pricing considerations for backpacking water filters

Budget

Low-cost water purification or filtration systems cost about $10 to $29. This price band includes chemical treatments like Potable Aqua tablets, Aquamira water treatment drops, the Lifestraw, and the Sawyer Mini.

Mid-range

You can expect to pay between $30 and $80 for most backpacking water filters and purifiers. Options include the Katadyn BeFree, and Grayl Geopress.

Premium

High-end options cost between $81 and $350 and feature exceptional performance, capacity, and durability, like the Platypus GravityWorks.

How we chose our top picks

All of the backpacking water filtration and purification devices recommended in this review were field-tested by your trusty crew of Task & Purpose gear reviewers. We take our time to get to know each backpacking water filter’s strengths and weaknesses and check out the reviews of other experts just to make sure we’re not missing anything.

FAQs on backpacking water filters

You’ve got questions, Task & Purpose has answers.

Q: What’s the difference between a purifier and a filtration system?

A: Purifiers tend to nuke all pathogens to include viruses, while filtration systems generally remove all bacteria and protozoa larger than 0.1 microns, but not viruses.

Q: Is a gravity or squeeze filter better?

A: It depends. Do you like to take a break while filtering water? Use a gravity system. If you like to get your water and go, use a squeeze system.

Q: Why do I need to protect hollow tube filter cartridges from freezing?

A: When water freezes, it expands and can damage the tubes. When the tubes get damaged, they don’t filter well and could let pathogens get through. When pathogens get through, you get the shits or worse.

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