Best Backpacking Water Filters of 2025

A bacteria-filled beach. A muddy wetland. Glacial silt runoff. The best backpacking water filters have to be able to handle some pretty gnarly water sources without clogging or breaking. I tested the 20 backpacking water filters in this story by taking them to three different water locations, pumping three liters of water through each filter. After each round, I timed how long it took each filter to handle a liter of tap water before continuing to the next round. At the end of all three rounds, I weighed each filter. 

Additional input on ease of use and durability were provided by members of the Outdoor Life backpacking gear testing crew over three days of hiking through the Goat Rocks Wilderness of Washington State. 

Best Backpacking Water Filters: Squeeze-Bag Filters

Best Overall: Sawyer Squeeze

For a long time, it was hard to choose a winner between the Sawyer Squeeze, the Platypus QuickDraw, and the Katadyn BeFree. Each managed to slightly one up the other in key categories, like weight, price, and flow rate under a variety of conditions. But it wasn’t enough of a difference to put a filter over the top. 

Sawyer changed all that by partnering with backpackers’ favorite water bottle brand: Cnoc. Right now you can choose between a two liter bladder and their classic Vesica bottle (essentially a collapsible Smartwater bottle for the uninitiated). I tested both, and personally prefer the bladder for its ease of use. Not only was it easy to fill and easy to squeeze, I could even hang the bottle up on a low branch thanks to the loop in the plastic closure, creating an impromptu gravity filter — which honestly worked better than some of the actual gravity filters I tested. But most backpackers will likely prefer the familiarity of the bottle, which you can attach the filter to and just drink straight out of. Just note that it’s noticeably more annoying to use the Cnoc bottle to filter several liters of water at a time. 

The rest of the Sawyer filter remains as excellent as ever. It performed well in my testing under a variety of conditions, from murky swamp water to silt-filled rivers. It’s easy, and quite effective, to backflush, quickly restoring flow. And it remains one of the more affordable options I’ve tested. If you already have a bottle system you like, or just need to replace the filter element, Sawyer also sells a filter without any accompanying bag. 

Best Tasting: Katadyn BeFree AC

There is a lot to like about the Katadyn BeFree AC. It’s been a standout performer during testing, handling every water source I’ve thrown at it at a level that will satisfy even the thru-hiking set. The Katadyn BeFree is also very lightweight, and requires no tools to clean its filter beyond a bit of clean water. The AC version of this filter is also noticeable in that you can add a carbon element to it that will improve the taste — pretty handy if you find yourself drinking out of a cow trough one too many times. 

Whereas previous iterations of this filter had a too-flimsy bottle cap (you could just snap it off), this one errs too far in the other direction. It’s very sturdy, but unfortunately, very difficult to use. I almost couldn’t flip it up just using my hands, and ended up resorting to leveraging it against a table, like I was opening a beer bottle. (My husband was able to open it with only moderate effort, so this is clearly a hand strength issue on my part.)

I’ve also had mixed success with the “swishing” method for cleaning this filter in the past. Sometimes it works great to restore flow; other times it makes flow worse. Expect to replace this one more often compared to the likes of a Sawyer Squeeze or Platypus QuickDraw. But if you know the place you are headed to has questionable water options, the option to easily improve taste may be worth it.

Platypus QuickDraw

While the Platypus QuickDraw was a hair behind the Katadyn BeFree (without the carbon filter) after the initial round of testing, it was out in front of the pack at the end of testing. The only round where the QuickDraw struggled was in the mucky water of the wetland, although I didn’t backflush it until after the glacial runoff round as its flow was still ahead of the majority of filters. Once backflushed, its performance was restored to close to the level that it had out of the box.

Unlike the Sawyer Squeeze, you can backflush the Platypus QuickDraw with a Smartwater bottle. While I appreciated that I didn’t need a separate tool to backflush the Platypus QuickDraw (something I’m prone to losing), I did find that the cap to the filter prevented me from creating a flush seal with the clean side of the filter.

However, the soft pliable material of platypus dirty sack combined with the positioning of the filter element on the interior (rather than on the inside of the bag), made this the second most pleasant filter to squeeze water out of in my test (after the Sawyer Squeeze paired with the Cnoc bladder).

Best Lightweight: Sawyer Squeeze Mini

The mini-me version of the Sawyer Squeeze is the perfect filter for UL enthusiasts — small enough that it won’t take up much real estate in your backpacking backpack and light enough (even after the final weigh-in) that you can scrub an ounce or more off your spreadsheet. Even better, it’s so affordable that it wouldn’t hurt your budget much to just replace it each season. Where it wobbles, unsurprisingly, is in functionality. It takes about twice as long as the standard Sawyer Squeeze to filter a liter of water. Of course, if you plan to attach the filter directly to a SmartWater bottle and suck the water out from there, that might not matter much to you.

I used the provided dirty bag during testing and was impressed with its durability. Even after squeezing the bag as hard as I could to push the water out over ten rounds of filling and filtering to reach the desired five liters, the bag still looked like new. I only wish that it was larger—the bag that comes with the mini is 16 ounces rather than the standard liter. Something else I noticed during testing was that the filter itself did not appear to screw onto the bag correctly. Each time I tried to fix it, the angle would still be lopsided. Fortunately, there were no leaks during testing so this appears to be mainly an aesthetic concern. 

While the flow rate for the Sawyer Mini was not especially impressive (about four times as long as the Katadyn BeFree), I did appreciate that it came with a lightweight syringe to backflush the filter when it starts to clog too much. 

Best for Travel: Grayl GeoPress

I’ve tested both the Grayl GeoPress (in titanium) and the UltraPress (in plastic). Both these filters use the same filter technology, so you can expect similar performance under challenging circumstances. Both are offered in either plastic (polypropylene) or titanium. The latter of which is very expensive.

But let’s first look at how the Grayl works. It’s a bit like a French press. You pull out the inner tube, fill the bottle up with water to the desired line, and then push the inner tube back down on top of the water until it’s all pushed through the filter on the bottom. This works best if you put the water bottle on the ground and allow your body weight to do the work of pushing the water through.

While Grayl boasts a very fast flow rate for this bottle, the actual rate is very much affected by how much effort you put into it. Most people can expect a half liter to take about 30 seconds, while expending moderate effort. The filter itself is also unique, as it uses carbon to attract viruses using electroabsorption (which is a fundamentally different process than filtering them out, such as the MSR Guardian does). 

For backpackers, there are a handful of issues that add up to this being not quite the right choice. First off, it’s pretty heavy, even when taking into account the benefit of having a built-in water bottle. In the backcountry, this added weight goes up even more, as the last half inch or so of water in the Grayl doesn’t filter through the inner tube, and is simply left sitting at the bottom of the bottle after filtering. The filter itself also has a much shorter lifespan than other backpacking filters, with Grayl advertising that you can expect about 350 liters out of it.

During testing, the filter was very affected by our gnarliest testing site, the glacial runoff, suggesting that in less pristine parts of the backcountry this filter may last significantly less time than 350 liters. And when this filter starts to struggle, it becomes a real nightmare to try and use. At least with the squeeze bags you can sit down while you struggle away (and maybe even backflush!), with the Grayl you’re stuck standing up, throwing all of your body weight down on top of a tiny lid that’s only a few inches in diameter. 

But what about the virus filtering? Well, very few backcountry water sources are contaminated by things like rotavirus, because these are typically human-borne pathogens. Backpackers don’t need this kind of firepower. Here’s who does: anyone living in or visiting parts of the world where the water coming out of the tap isn’t trustworthy. That water is probably running clear, too, so the lifespan of the filter will be that much longer. If you’re looking for a travel water bottle that will protect you from just about everything, from e.Coli to giardia to cryptosporidum, this is the filter for you.

I’m a sucker for titanium as much as the next backpacker, so I was excited to check out the titanium version of the GeoPress in my second round of testing to compare to the polypropylene Ultrapress I had tested previously. After testing, I’ll be sticking with the polypropylene version. While the aesthetics of the titanium bottle are undeniably cooler than the plastic one, this doesn’t overcome the functionality challenges (or the price). The biggest issue here is usability. While it takes a little elbow grease to pull the inner tube with the connected filter out of the main housing on the polypropylene version, I struggled to get the inner tube out of the titanium version at all. And this doesn’t come with the typical titanium benefit — this version is heavier than the plastic version. 

Sawyer Micro Squeeze

The Sawyer Micro is right in between the Squeeze and the Mini. It doesn’t have the knockout performance of the Squeeze, but it weighs less. It had a better flow rate across my testing conditions than the Mini but it weighed more. For some backpackers, that may put it in a no-man’s land; for others, it could be the perfect Goldilocks product. 

One other advantage of the Sawyer Micro is that, like the Squeeze, you can pair it with one of Cnoc’s bladders. I particularly like how minimalist and utilitarian the Cnoc 750ml liter pouch it was paired with was. It’s very light (weighing only 3.1 ounces) and similar in function to the Sawyer dirty water pouches of yore. 

MSR Trailshot

The MSR TrailShot is slightly heavier, slightly pricer, and not quite as good as a performer as the best squeeze back backpacking filters, but its unique design makes it an interesting show for specific purposes. With the squeeze bag filters, the first step is to fill up the bag — sometimes easier said than done if you’re looking at a desert seep. But the TrailShot has an intake that is closer to a traditional pump filter, but shrunk down such that it could fit in almost any water source worthy of the name. That’s a game changer if you don’t have the interest or patience to sit around Macguyvering a solution to a hard to access water source. 

In testing, I found the hand squeeze mechanism of the TrailShot to be fairly tiring. By the end of the third round of testing, it was one of the filters I dreaded using. And while its performance was adequate for murky water sources (if not exceptional), it struggled with the glacial runoff, taking over four minutes to squeeze out a single liter. 

If you’re a hardcore trail runner, or just an exceptionally impatient person with exceptional hand strength, this filter might be the answer to your needs. But the vast majority of people will be better served by one of the high-performing squeeze bag filters on this list.

LifeStraw Peak Series

LifeStraw is one of the most well-known brands in water filtration, thanks to the ubiquity of their LifeStraw filter, which they distribute to school children in rural Kenya. Their Peak Series filter is a slightly more expensive, slightly better performing backpacking water filter compared to the original LifeStraw. They provide their Peak Series filters as part of a squeeze bag filtration setup; unfortunately, in testing it didn’t perform at the level of more popular models like the Katadyn BeFree, Sawyer Squeeze, or Platypus QuickDraw.

One advantage of the LifeStraw Peak Series is that you have the option to add on a carbon filter for an extra cost that can help improve taste. If you are traveling in areas where you’ll be sharing a lot of water sources with cows, or pulling water out of stagnant ponds, then this can help make your trip more pleasant. However, there were issues while I was testing the carbon filter option for the LifeStraw Peak Series. The first is that the carbon element, which is about the same length of the regular filter, screws onto the end of the existing filter. This means that the filter element inside the squeeze bag is nearly as long as the squeeze bag itself. It’s not terribly easy to squeeze all the water out of it with this setup, as you can’t roll down the bag as you go. The other issue is that while testing this filter set up, the bag for the LifeStraw Peak Series ended up with a small hole in it, forcing me to end testing of this element earlier than I had hoped. If you are interested in adding a carbon filter to your backpacking water filter to improve taste, go with the Katadyn BeFree AC. If you’re interested in removing heavy metals and other tricky contaminants, go with the Grayl GeoPress.

RapidPure Purifier+

The RapidPure Purifier+ was one of the worst performing filters in my test, taking over two minutes to filter a liter of water out of the box, and over five minutes after I tested it out at a murky swamp. While it was somewhat unique among squeeze bag filters for using activated carbon to help filter out viruses (the Grayl filters also do this), my sense is that the performance here is poor enough that you would be better off snagging some chemical treatment — like Aquamira – rather than dealing with this easily clogged squeeze bag filter. 

Best Backpacking Water Filters: Gravity Filters

Best Gravity: Platypus GravityWorks

At its core, all a water filtration system needs to do is move dirty water through a filter, without inadvertently contaminating the clean water vessel on the other side. One of the most popular styles of backpacking water filters leans into this simplicity: all a user has to do is fill up a plastic bag with dirty water, attach the filter, and then squeeze the water through into their drinking vessel.

The idea behind a gravity filter is fairly straightforward, instead of squeezing or pumping dirty water into your drinking vessel, let gravity do the work for you. After filling up the dirty bag—which holds up to three liters in the case of Katadyn—you then elevate it by placing it on a large rock, hanging it in a tree, or even holding it yourself, whatever works. The higher the water is, the faster it will flow through the filter, but it will work as long as the bag itself is higher up than the end of the outlet hose. Then you can just walk away while gravity forces the water from the dirty water sources into your clean container.

All the gravity filters in my test came with a flask of at least three liters, which is nice if you are traveling with multiple people, as it reduces the number of rounds of filling up your dirty flask that you need to do. The Platypus GravityWorks takes this a step further, with a dirty flask capacity of four liters. Even better, it comes with a second bladder to filter your clean water directly into it.  

In testing, the GravityWorks took about twice as long to filter a liter of water after the first stage of testing as the Katadyn BeFree; however, it was nearly unable to process the glacial runoff, taking an hour to filter a liter of water after the third stage of testing. After using about six liters of water to backflush the GravityWorks, which is accomplished by simply raising the clean water reservoir above the dirty reservoir and allowing the water to flow backward, the flow improved significantly, but not to the level of the Katadyn BeFree Gravity.

The reason I’m recommending the Platypus GravityWorks over the Katadyn BeFree is that it’s set up to be a set-it-and-forget-it. You can fill up the dirty bag, set up the filter, and then leave for however long you need as you attend to other camp chores. With the other gravity filters here, you’ll need to monitor more closely, swapping out a reservoir as it starts to fill up. However, if you don’t mind babysitting your gravity filter, then the lighter weight and faster flow of the BeFree might be a better choice for you.

MSR Guardian Gravity

A gravity filter that can remove viruses: this one is beyond impressive. Unfortunately, it also comes with some drawbacks. The biggest is that its tiny pore size (.02 so that it can catch those microscopic viruses) means that the filter slows down fairly rapidly, even when the water sources it’s dealing with aren’t overly challenging. The MSR Guardian Gravity handles this by building a backflushing mechanism into the filter itself. You simply stopper the main filter, and unstopper the backflush mechanism. After a few minutes you switch back and continue on your way. This works well, but I was surprised by how often I had to do it — unlike the rest of my filters, which were only backflushed after the second and third rounds, I backflushed this one after the first round and was rewarded with a flow that was faster than what I had started with. For most water sources, you should plan to backflush every 3 to 4 liters — more often if it’s exceptionally dirty, as I ended up doing. Backpackers should note that this one is also fairly heavy compared to other gravity filters I’ve tested. 

If you know the water source you’ll be using is contaminated with viruses, and you feel strongly about avoiding chemical treatment, this is a great hands-free option. For most people, it’s likely overkill. But the fact of its existence is a testament to the problem-solving creativity of the folks at MSR. 

Katadyn Gravity BeFree

Of the three gravity filters in my test, the Katadyn Gravity BeFree had the fastest flow both when initially unboxed and after the final stage of testing. It was also lighter than the other two models in my test by several ounces. 

One small, but potentially significant, difference between the Katadyn BeFree and the Platypus GravityWorks and LifeStraw Peak Series Gravity is that the hang strap is not attached to the water flask when the gravity is first unboxed. This strap, however, should not be considered optional. The bail handle at the top of the water flask is not intended to be slung over a branch, and is too small for the branch size that you would need for the filter to be safely suspended. 

Another difference between the Katadyn Gravity BeFree and the other two filters in my test is that it is not designed for backflushing (which could damage the fibers), but the filter can be cleaned by carefully swishing it in water. While the filter did appear cleaner after I swished it, oddly, the time it took to filter a liter of water increased by a minute (I reran this test to confirm the results).

LifeStraw Peak Series Gravity

I was admittedly disappointed in the LifeStraw Peak Series Gravity Filter. While it performed on par with the Kataydn Gravity BeFree and Platypus GravityWorks out of the box, it started to slow down during the first test, contaminated lake water. Whereas the other two filters could still filter a liter of water in about a minute after that test, the LifeStraw Peak Series Gravity took over six. After the wetland water source was filtered, the LifeStraw Peak Series Gravity was clocking 13+ minutes. 

This one may be less expensive than the other two gravity filters, but my testing shows that this is not a great value. 

Waterdrop

If you search for “backpacking water filter” on Amazon, you’ll almost certainly come across the Waterdrop filter. This brand isn’t as common in the backcountry, as the company’s primary focus is on water filtration for the home, but the model that I tested is designed for backpackers to use interchangeably as a gravity filter or squeeze bag. For simplicity’s sake, I tested it as a gravity filter. 

Before we go even further, please do not buy this water filter for traveling in the backcountry. Their website says they remove 99.99 percent of bacteria. While that sounds impressive, the standard is for 99.9999 percent. You are at risk of illness if you rely on this water filter to protect you from something like E.coli.

That the Waterdrop cannot be relied on for actual filtration is only one if its drawbacks: it’s also a damn slow filter. It does get faster when you backflush it — surprisingly, flow was faster after my first backflush than it had been originally. However, you need running water to do this, which isn’t always available. Another practical issue is that the plastic stopper on the tube running from the filter was not effective at actually stopping the water’s flow. 

If you’ve got nothing better to do than wait around for an hour or two while all your water finishes filtering, and then also treat it with chemicals so you’re actually protected from bacteria and protozoa, this might not bother you too much. But most backpackers have better things to do. If you’re after a gravity filter, go for either the Katadyn BeFree (if you value lightweight) or the Platypus GravityWorks (if you value convenience). If you’re after a squeeze bag, grab a Sawyer Squeeze, which is only nominally more expensive. 

Best Backpacking Water Filters: Pump Filters

Best for the Apocalypse: MSR Guardian

For backpacking water filters, protection against viruses, including norovirus and rotovirus, typically comes with a tradeoff—if you want a filter with a small enough pore size to weed those suckers out, you better be prepared to put in some serious elbow grease. But the MSR Guardian manages the hat trick, filtering out viruses at a fast flow rate with the same, or even less, elbow grease required as from other filters.

Part of this due to a unique feature to the MSR Guardian: instead of directing all of the water out through the bottom of the filter with each pump, a portion of the water is directed back through the filter—essentially backflushing the filter with each pump. During testing, this meant that the filter had the same performance during the last round of testing as it did during the first: forty-five seconds for a liter of water.

I was also impressed with how easy the MSR Guardian was to use straight out of the box: after it had been unmoored from its packaging, I simply unscrewed the cap on the bottom of the filter, plopped the intake filter into my pool of water and started filtering water. Besides the prefilter, which can be a bit difficult to position in the water source due to a 90-degree angle, the biggest downside to the Guardian is its cost, and its weight: it was about ten times as expensive as other comparatively fast filters (the Katadyn BeFree, Platypus QuickDraw, and Sawyer Squeeze) and five times as heavy. But if you’re looking for a no-brainer filter that can remove the full spectrum of bacteria, protozoa, and viruses from your water with basically no maintenance required, then this is the filter for you. 

Katadyn Pocket

The Katadyn Pocket was, along with the MSR Guardian, one of the most expensive filters I tested. While the Pocket struggled with the testing protocol, taking over 11 minutes to filter a liter of water after the final round, where it really shone was after I had cleaned it. This filter was 10 times faster after cleaning than before, which suggests that, if taken care of correctly, could last for many years. 

However, the MSR Guardian is the same price, filters viruses, and cleans itself. If you aren’t concerned with the weight of your filter or the price, then that is going to be the best pick for you. 

Katadyn Hiker Pro

I’ll admit: I broke a Katadyn Hiker Pro years ago after using it in water containing glacial runoff. So I wasn’t surprised to see that it struggled with that portion test, needing over four minutes to filter a liter of water. And while this wasn’t a part of my testing protocol, the sheer hassle of all the tubes and nozzle caps for this filter makes it a non-starter for me. For half the price, less weight, and way less hassle, you can pick up a squeeze bag filter, including the Katadyn BeFree. Do that.

Katadyn Vario

While the Katadyn Vario clocked in a truly impressive time out of the box and in the first two rounds of testing, it struggled in the final round of testing, after being subjected to glacial silt. Worse, after I backflushed the filter (following manufacturer instructions), it stopped working entirely. If you are dedicated to old-school filter-style pumps, but don’t want to pony up for the MSR Guardian, this is one of the better options. Just be sure to baby the filter in more challenging water conditions to preserve it for the long haul. 

MSR MiniWorks

Given the ubiquity of the MSR MiniWorks in the backcountry, I was surprised at its poor performance in my test. It was never a particularly fast filter compared to other options, and it clocked one of the worst times during the test at the wetland before completely breaking while I was filtering glacial runoff. I have no doubt this filter was one of the best in its class when it was originally released, but it has since been eclipsed by other, less expensive options, including the Platypus QuickDraw from MSR’s sister company.

Best Backpacking Water Filters: Non-Filter Treatment

Best Chemical Treatment: Aquamira

There are plenty of backpackers who refuse to deal with the hassle of any kind of backpacking water filter, preferring instead to opt for chemical treatments. Of these, the most popular is Aquamira. The biggest reason is simply that, or all the chemical treatment options available, Aquamira has virtually no taste. If you’ve ever tried to go an entire trip with bleach or iodine-flavor water, you know what a game changer that is. 

Unlike bleach and iodine, however, the process for using Aquamira is a little involved. The treatment comes in two separate bottles, which must be carefully mixed together in the larger of the two bottle caps. You then leave it sitting for five minutes, so the chemical reaction can get started, before adding it to your water bottle. Twenty-five minutes later, you are ready to hydrate. 

For some backpackers, this tedious procedure and long wait is a small price to pay to avoid the pitfalls (mainly, clogging) of traditional filters. If that sounds like you, then Aquamira is an excellent and reasonably affordable option. 

Katadyn Steripen Ultralight

Steripens, the most popular form of UV water treatment for backpackers and backpack hunters, are one of the strangest water treatment options on the market. Whereas chemical treatment and water filter options make some kind of intuitive sense, the eerie glow of UV treatment seems almost magical. For some people, this is appealing; for others, it’s a nonstarter.

Which gets a bit at the heart of the experience of using a SteriPEN. I used the original version of the SteriPEN for years and became fairly familiar in that time with its pitfalls: don’t pack it away wet, warm it up before using it in especially cold water, watch the sensors carefully when submerging. By carefully following these rules, we could get about as much reliability out of our SteriPEN as users of the squeeze bag filters were getting.

On our testing trip, I handed off this latest version of the SteriPEN to one of our testers while going to put away my tent. When I came back, 15 minutes later, she still hadn’t managed to filter a liter of water. I watched her fifth attempt to see if I could troubleshoot what was going wrong, but I couldn’t see why she was getting error readings (or recall in the moment what the different flashes of color meant).

Then I tried it and it worked perfectly. This about sums up most people’s experience with SteriPENs. When they work, it’s like magic. When they don’t work, you’ll want to pull your hair out. If you do go this route (it is the only non-chemical treatment at this weight that’s effective against viruses), then be sure to test it out extensively at home and take a backup water treatment method along for a few trips until you are comfortable with it.

Aquatabs

For years, I carried a bottle of iodine in my first-aid kit. I almost never used it (iodine tastes terrible), but in the event that my water filter broke, I wanted to have something surefire on hand. While today’s backpacking water filters are much more reliable than the old pump models of yore, carrying a few tabs of backup water treatment still brings me peace of mind on longer, more remote backcountry treks.

Like Aquamira, Aquatabs take about 30 minutes to take effect, although no premixing is required here. But while Aquamira has no discernible flavor, there is a slight chemical flavor that goes along with the Aquatabs (although our testing group didn’t find that they had the same unpalatable flavor as other reviews). While this is only a minor concern in a true survival scenario, long-term use of Aquatabs could result in individual backpackers inadvertently hydrating less than is optimal for their environment.

While Aquatabs won’t be replacing a water filter in my kit anytime soon, they will be going in my first-aid kit as a backup water treatment option for longer treks.

Katadyn Micropur

One protozoa that is tough for chemical treatments is cryptospordium. While the Katadyn Micropur was one of the few chemical treatments that was effective against this bug, it does take four hours to treat. That makes this a no-go for most backpackers, although backpack hunters with a bit more leeway in how long they plan to stay in one spot for may find it a useful option.

Potable Aqua

Is there any more classic water treatment option than iodine? But, of course, there is a reason this one has fallen out of favor: it tastes terrible and, long-term, it’s terrible for you. The new taste-neutralizer tablets help with the former issue (some) but can’t do much about the latter.

How I Tested Backpacking Water Filters

Before I even began testing, I interviewed the folks at MSR, LifeStraw, and Katadyn about how they guarantee that their filters are indeed removing bacteria and protozoa (and in the case of a few of them, viruses). All of them engage in rigorous testing, using EPA or NSF standards, both in their own facilities and through third parties, like BCS Laboratories out of Florida.

I visited the MSR facility where they showed me the lab where they not only grow E. coli bacteria, but also a virus that attacks E. coli, to test the performance of their Guardian filter. The thoroughness of this testing is not something that can be easily replicated in the natural environment, where the pre-existing levels of bacteria, protozoa, and viruses are unknown. As such, my testing did not look at how well the filters dealt with bacteria, protozoa, and viruses, because all the filters in this review use EPA or NSF standards.

Something else that you’ll often see on the packaging of backpacking water filters is the number of liters per minute that they filter. This number, however, only reflects what the filter is capable of doing right out of the box—not after you’ve taken it out on a couple of backpacking trips—or 20. The brands of course are testing to ensure that the filters can withstand a certain level of grit, but it’s rare to learn what the flow rate of the filters are after they’ve been exposed to some less-than-ideal water sources, let alone how much grit and sediment and muck a filter can take before it craps out completely. So my testing looked at what conditions the backpacking filters can withstand and still return a reasonable (or any) flow rate.

To start, I called in or purchased the most popular backpacking water filters available, along with corresponding models from their competitors. Before I began testing the filters out in the field, I first timed how long it took each to filter one liter of water out of the box. Generally, these times corresponded to the advertised times of the manufacturers. During this process, I also noted how complicated the filter setup was out of the box. 

Then I took the filters to a public beach in Bellevue, Washington, which had been closed due to high levels of fecal matter (three times more than what’s considered safe for swimming). Here I filtered five liters of water through each of the filters in my test.

In addition to the recorded high levels of fecal contamination, the water was also fairly scummy.

At the end of the first round of testing, I took the filters back home and measured how long it took to run a liter of water through each, and how that compared to the out-of-the box test. In most cases, there was a noticeable, if not significant, effect on the length of time it took to filter one liter of water. Ironically, some filters measured a faster time at the end of the initial round of testing than they had at the start; my impression is that this is the result of my becoming more efficient at using the filter with practice.

The second round of testing took place at Narbeck Wetland Sanctuary, just north of Seattle, Washington. This is a classically beautiful swamp, with plenty of water but all of it gunked up by the dirt and tannins and life teeming beneath the surface. Here we would see how well the backpacking water filters responded to the mucky water sources that those in the backcountry are sometimes forced to resort to. I filtered three liters through each of the water filters at this site, and then headed home to record how long it was taking each water filter to push water through.

Unsurprisingly, some of the filters were really struggling at the end of this test. For the filters that took over two minutes to process a liter of water, I followed manufacturer directions to backflush (pushing water backwards through the filter) or otherwise clean the filter, noting that some filters could not be cleaned or backflushed.

Then I retested those filters (the results are noted in a parenthetical in the below table) to see how effective cleaning the filters was at establishing water flow. The two filters that took over five minutes to process a liter of water at the end of the second round of testing, the LifeStraw Peak Series Gravity and the RapidPure Purifier+, were removed from the test at that time.

The final testing site was the Puyallup River, accessed at the town of Orting, Washington. At first glance, the Puyallup looks like any other muddy river. But the Puyallup gets its color from glacial sediment, an extremely fine silt that stays suspended in the water. This sediment also works its way into the inner workings of filtration systems like nobody’s business. No one would choose to filter this kind of water unless there was no other option available; sometimes, there is no other option available.

Unsurprisingly, many of the filters struggled with cleaning three liters of water during this test, and one (the MSR Miniworks EX) was removed from testing as it simply clogged up and stopped working. At the end of this round of testing, the filters were measured to see what their flow rate was. Next, the filters, where possible, were also backflushed, or otherwise cleaned, and then had their flow rate measured again. (Note that some of the times for this stage were again faster than the initial flow.

While I made an effort to standardize the amount of elbow grease I was putting into each filter during the timed test, it’s clear that I was putting more elbow grease into the final stage of testing than I did straight out of the box). The final step of this test was to reweigh each of the filters to assess how their weight had changed from the start of testing. I pumped out as much water as I could from each filter and then placed the filters in an enclosed room with a dehumidifier to remove excess water (without drying out the filter components themselves). After an hour, I took them out and reweighed them.

In April 2025, I put seven new products through my testing protocol. For the first test — bacteria beach — I headed to the most polluted lake in my area at the time, Cottage Lake, which was closed to swimming due to algae bloom and subsequent cyanotoxins polluting the water. For the wetland portion, I again returned to Narbeck Wetland Sanctuary, which was as murky as ever. What was somewhat less murky was the Puyallup River near Orting, WA. While the river water was extremely silty in my original testing, the spring run off ran much clearer than I had anticipated. Unfortunately, this meant that testing conditions were not challenging enough to provide useful information. I’ll be taking these filters back in late summer for a fresh test in proper silty conditions.

Testing Results

Squeeze Filters

Gravity Filters

Pump Filters

Where testers did not have a full liter capacity, I tested the time to filter a half liter and doubled it.

Additional testing was done on several chemical and UV treatment options as part of the inaugural Outdoor Life backpacking gear test. While chemical and UV treatment options do not remove any dirt or grit or microplastics from water sources, they can render bacteria, protozoa, and even viruses inert, making water safe to drink.

Things to Consider Before Buying Backpacking Water Filters

Bacteria, Protozoa, Viruses, Heavy Metals, and PFAS

Where once backpackers only concerned themselves with giardia, today there are a host of other concerns, including norovirus, heavy metals, and PFAS. Let’s take a look at which backpacking water filters can handle which types of contaminants, and when you need virus and heavy metal protection.

All of the backpacking water filters I tested remove bacteria and protozoa. That’s great news because two of the most common backcountry water contaminants are E. coli (a bacteria) and giardia (a protozoa). In most popular backpacking locations through the United States, this is all you’ll need protection against. 

Viruses

The most common viral contaminant is norovirus. While this is typically thought of as a frontcountry contaminant, it can (rarely) occur in water sources in the backcountry. This is almost always the result of human feces contaminating water sources. 

• Grayl UltraPress
• Grayl GeoPress
• MSR Guardian
• RapidPure Purifier+
• All chemical treatments

Heavy Metals

While heavy metals do occur naturally in the environment, contamination is typically the result of industry. Heavy metals differ from bacteria, protozoa, and viruses as it’s unlikely to harm you during your trip, but accumulation in your body can result in damage to your organs. 

A filter alone — even an advanced one like the MSR Guardian — cannot remove heavy metals. Backpacker water filters that remove heavy metals typically use activated carbon. While these filters are somewhat effective at removing heavy metals from water sources, they are not perfect: certainly nowhere near the 99.9999% rating of a typical filter against the likes of bacteria and protozoa. Your first line of defense is to not drink water from sources known to be contaminated with heavy metals. But if it is unavoidable, or unclear if contamination is an issue, then these will provide some protection. 

• LifeStraw Activated Carbon Filter Attachment
• Grayl UltraPress
• Grayl GeoPress

PFAS

While PFAS contamination has been an issue for many years, it’s only recently that backpackers have realized that backcountry water sources may be at risk. That’s because, unlike other contaminants, rainwater can contain PFAS. At present, there are very few backpacking water filters that can remove PFAS; however, the reality is that most backcountry sources will not be contaminated, or contaminated at such low levels as to not pose significant harm to human health. You should take extra care around water sources that are near military bases and wildland firefighter training facilities. That’s because past use of AFFF firefighter foam led to intense PFAS contamination. 

• Grayl UltraPress
• Grayl GeoPress

Weight of the Best Backpacking Water Filters

While it can be tempting to grab the biggest, baddest water filter on this list (the MSR Guardian), the reality is that most backpackers will be better served by carrying something lighter weight. The more you can keep your pack weight down, the farther you’ll hike and the more fun you will have. 

Filter Maintenance for the Best Backpacking Water Filters

As my testing shows, cleaning out your filter can make a huge difference in performance. If you don’t want to shell out for a new filter every season, be sure to read the directions and hold onto any plungers or other necessary pieces. Unless you are going on an exceptionally long hike or expect to filter only glacial silt, you likely won’t need to bring these pieces with you on each hike. 

FAQs

Final Thoughts on the Best Backpacking Water Filters

The best backpacking water filters produced by reputable brands like MSR, LifeStraw, Katadyn, Platypus, RapidPure, and Grayl provide excellent protection against waterborne diseases in the backcountry. Which filter is right for you will depend in large part on whether you prioritize cost, weight, or long-term durability.