The Best Backpacking Water Filters
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Once upon a time, you didn't need such a newfangled contraption as a backpacking water filter. Getting a refreshing drink meant meant dipping your tin Sierra cup (or Nalgene) in any stream and taking a nice, cool, clear drink. Unfortunately, thanks to the prevalence of giardia and other fun protozoa and bacteria, that's now likely to have you running behind every tree.
Thankfully, the solution is pretty simple. Grab one of these water filters and put it between you and that ice cold stream. Many of the filters we've tested aren't much more complex in operation than dipping a cup in a stream. In fact, our first two picks allow you do pretty much just that, drinking clean, cool water almost as easily as John Muir did.
Once you've purified your water, I recommend making a nice hot cup of coffee and putting it in one of the Best Travel Mugs. Don't forget to check out the rest of our outdoor buying guides, including the Best Puffer Jackets and the Best Sunglasses.
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The Difference Between Water Filters and Purifiers
Water filters work by physically straining out all the critters, bacteria, viruses, and even chemicals. While designs vary, the basic idea is that water passes through an internal filter element with microscopic pores that stop all the things you don't want while letting the water through. These filters are measured in microns.
Eventually, the filters get clogged and need to be cleaned or replaced. Filters are the best choice for backpacking in the US most of the time. They're the lightest, and they're capable of filtering out bacteria and protozoa (like giardia), which are the primary source of infection in backcountry water sources.
Water purifiers don't filter. They kill live organisms, usually with chemicals (iodine is the most common). This eliminates even viruses. There are also some purifiers that use ultraviolet light rather than chemicals, but the result is the same. If you're headed abroad, especially to less-developed areas, you might want a purifier rather than just a filter, but there will be particulates and other junk left in your water. It might also retain its iodine taste.
What to Look for in a Water Filter
The right water filter or purifier depends on where you're going and what you're doing. Before we get to the specifics, here are some general things to consider when choosing a water filtration system for the backcountry:
- Portability: Pack space is limited, so aim for the smallest lightest water filter you can get that still does the job.
- Flow Rate: The smallest lightest filter might also be the slowest. Who wants to waste a bunch of time filtering water? Check the specs to see the manufacturer's claims about filtration speed. Keep in mind that as you use it the filter will get progressively more clogged and slower. Most filters include some method of cleaning it in the kit.
- Field Maintenance: How difficult is it to clean in the field? Do you have to carry a backflushing device? Is there a back-flushing device or does it need to be back-flushed with a tap? Different filters require different methods of cleaning.
- Ease of Use: Do you have to pump water through, or can you squeeze? Gravity filters are another nice option. It's much easier to let gravity pull the water through the filter, although it's much slower. Also consider whether you can connect a filter to your preferred water bottle or water bladder. (Sometimes third-party adapters are available for more popular water filters.)
- Capacity: Consider how much water a filter can process before it needs maintenance or replacement. This is more of an issue if you're thru-hiking, traveling for extended periods of time, or traveling with a group.
- Durability: Does the filter stand up to life on the trail? This is where we come in. We've beat the heck out of these filters in our testing to see what they can take and continue to function.
Water Filtering Tips and Tricks
A filter alone won't give you that sweet clean, clear water you crave. You have to know how to use it and how to avoid some common mistakes.
- RTFM: Every filter has its own flow and means of avoiding cross contamination. While most of them can be figured out from the labels on the filter and bottle, it pays to read the direction a few times and practice filtering with tap water before you're in the field.
- Label your bottles/bladders: Keep dirty water and clean water containers separate and clearly labeled. I like to use distinct bottles from different brands so I can remember which ones are clean and which are dirty.
- Prefilter: Prefiltering means removing the large debris before you filter water. This is especially important if murky water (a lot of sediment) is all you have around. Prefiltering will keep that sediment out of your filter, prolonging its life. You can buy separate prefilters for most of the filtration systems below, but I generally just use a spare bandana.
- Don't freeze: Many filters are destroyed by freezing. For winter camping, I typically just melt snow, but if you're likely to encounter freeze temps in spring or fall, make sure you bring your filter to bed and keep it in your sleeping bag with you overnight.
- Photograph: Scott Gilbertson
Best for Ultralight Hikers and Backpackers
Sawyer Squeeze Water FilterA favorite of ultralight hikers, backpackers, bikers, and travelers, the Sawyer Squeeze filter is the gold standard in water filters for anyone concerned about weight and universal compatibility. The Squeeze weighs just 3 ounces, has a filtration level of 0.1 microns (which gets rid E. coli, salmonella, giardia, cryptosporidium, and other common problems), and claims to filter 100,000 gallons of water before it needs replacing. The Squeeze also connects to any 28-mm diameter soda bottle (your basic 20-ounce Coke bottle, for example), which means you never have to worry about damaging a bottle, since a replacement can be easily found anywhere in the world.
You can buy the Sawyer Squeeze as either the filter alone or as a kit with a couple of water bladders and connecting hoses. The kit-included bladders work fine, but I generally skip them and filter into a Smart Water bottle. As the name suggests, the Squeeze is meant to be squeezed, though it does work fine as a gravity filter, just slower.
After years of testing and tweaking, my setup for the Sawyer Squeeze is a 2L Cnoc VectoX water bladder ($25) for dirty water, which connects directly to the Squeeze, and then two Smart Water bottles for my clean water, which connect directly to the filter outlet. For trips with infrequent water sources, I bring an additional 2L HydraPak bladder ($25). This setup allows me to get two liters of clean drinking water in about 4 minutes if I squeeze, and more like 6 to 8 liters if I hang it and let gravity do the work. The speed does fluctuate quite a bit based on how clean the filter is, and these numbers are based on a freshly cleaned filter.
Cleaning is the one downside to the Sawyer. To give it a good cleaning you'll need the included back-flushing syringe, which is regrettably bulky. My experience has been that, if you can find good, clean sources of water, without a ton of silt or debris, the Squeeze easily goes seven days without needing a cleaning. For longer trips, I pack the syringe. It's also worth noting that there is Sawyer Mini ($17) is even lighter but less robust. In my testing, the weight savings of the Mini is trumped by the faster flow rate of the Squeeze, but if you're at the cutting-the-handles-off-toothbrushes stage, the Mini is a better choice.
Specs Weight 3 oz. (85 g) Filtration 0.1 micron Type Hollow fiber membrane Speed ~0.5 liter per minute - Photograph: Scott Gilbertson
Best for Simplicity and Convenience
Katadyn BeFree Water FilterThe Katadyn BeFree Water is one of the lightest filters on the market (2.3 ounces, or 65 grams, for the filter and bottle) and a great option for when you want to go as light as possible, such as trail running or day hikes. The design of the BeFree is part of its appeal. The filter is inside the collapsible container. Scoop up some water into the container, screw on the lid, and drink. The collapsible soft bottle rolls down to a tiny package, making it easy to stash in your pack. While that's nice, the soft bottle does feel less durable, and many people prefer to pair their BeFree with something stronger like a Platypus bottle or the Cnoc mentioned above. (Just be sure to get the 42-mm version to fit the BeFree threads.)
The BeFree is the fastest flowing filter I've tested. It can crank out 2 liters of fresh, clean water per minute, which means in practice that drinking out of it is no different than drinking from a bottle of water. As with all filters, the flow will decrease as the filter clogs, but the good news is that to clean the BeFree you just swish some water through the filter and you're good to go. That's the theory, anyway. In practice, I've seen many reports of people's BeFrees clogging prematurely. I have not experienced any issues yet myself.
My main issue with the BeFree is the 42-mm cap size. If something goes wrong on a longer trip, it's going to be hard to find a replacement bottle/bladder. I'd love to see Katadyn move to the more universal 28-mm size. That said, I keep a BeFree in my day-hiking kit because it weighs next to nothing.
Specs Weight 2.3 oz. (65 g) Filtration 0.1 micron Type Hollow fiber membrane Speed ~2 liter per minute
- Photograph: Scott-Gilbertson
Best for Large Groups
MSR AutoFlow XL Gravity Water FilterThis MSR Gravity filter changed backpacking for me. Pumping water for a family of five, day after day on the trail, sucks all the fun out of backpacking. This filter eliminated the pumping and returned my sanity. All you have to do with this filter is scoop up 10 liters of water in the dirty water bag, attach the hose, connect your water bottle, and sit back and relax.
The filter is good enough to keep you safe from all the usual protozoa and bacteria, and the flow rate is a solid 1.5 liters per minute when the filter is clean. The 1,500-liter capacity is on the low side, and replacement filters are around $50, but frankly, this expense is well worth the convenience. My only real gripe about the MSR Gravity filter is that the filter clogs with sediment rather quickly (in part because you're sending 10 times the water through it each time you use it, relative to the rest of these filters) and requires regular back-flushing. It's actually no worse than any of the rest of these, though. It just feels that way because it filters so much more water.
Specs Weight 12 oz. (340 g) Filtration 0.1 micron Type Hollow fiber membrane Speed ~1.5 liter per minute - Photograph: MSR
Best for Shallow Water
MSR TrailshotThe MSR Trailshot is a lightweight hand pump with a hose that makes it easy to filter water from shallow streams where filling a bottle-style filter is difficult or impossible. It does take some hand strength to pump the Trailshot and it would not be my top pick for an extended trip. After you pump about 2 liters, your hand is going to be tired. But if you're in areas with frequent but not large water sources—alpine streams, for example—this works really well. I've used it on many a day hike where I knew there was a water source, carrying less water than usual and drinking direct from the stream. My main gripe about the Trailshot is that it's expensive for what it is. The Sawyer and the BeFree are a better value.
Specs Weight 5.2 oz. (148 g) Filtration 0.2 micron Type Hollow fiber membrane Speed ~1.5 liters per minute
- Photograph: Aquamira
Best Chemical Treatment
Aquamira Water Treatment DropsIf you're hiking anywhere with extra-sketchy water—for example, areas where cattle share water resources or where you don't know anything about what's upstream—chemical purification is the way to go (in extreme cases, go with filtration and then purification). Aquamira is a chlorine dioxide treatment that kills everything, including viruses. The downside is that your water tastes a bit like a swimming pool. Part of the reason I like Aquamira is that it has the least taste of any of the chemical treatments I've tried. I relied on Aquamira extensively while trekking in India and Laos.
Aquamira is also quite reasonably priced. However, if you just want an emergency backup in case your filter breaks during a backpacking trip, Katadyn's Micropur tablets ($16 for 20) are a better option, because they're smaller and lighter than the Aquamira.
Best for Sketchy Water
MSR Guardian Water FilterWhen just about anything could be lurking in the water, the MSR Guardian is the filter/purifier to get. It's expensive and heavy and requires pumping, but the Guardian is the perfect filter for handling anything. The Guardian filters down to 0.02 micron, which will remove even viruses. It's also designed to be self-cleaning, which makes field maintenance incredibly easy. It's rated to pump 10,000 liters, which is good because replacement cartridges are very nearly as pricey as the whole pump ($239 at REI).
The Guardian is a pump filter, but if your arm is getting tired just thinking about the old days of pumping water, fear not. The flow rate is actually the best of any filter in this guide. It does take some effort compared to a gravity filter, but it's not too bad. Because it screws right onto a Nalgene bottle, it's pretty easy to crank out a couple of liters in hardly any time at all. You can use a hose to pump into any bottle if you don't have a Nalgene, though this does make the process a little more awkward.
I think the Guardian is overkill in most of the US (I'm sure there are exceptions), but this is the filter I bring when traveling abroad. I haven't tried it, but there is also a gravity-fed version of the Guardian ($420). It's essentially the same as the MSR Gravity Filter above. It just runs the water through the Guardian filter/purifier.
Specs Weight 22 oz. (617 g) Filtration 0.02 micron Type Medical-grade hollow fiber membrane Speed ~2.5 liters per minute
- Photograph: Scott Gilbertson
Best Discrete Filter
Epic Water Filters Nalgene OGI like Epic's water filter because, from outward appearances, it just looks like a Nalgene bottle with a straw lid. This is handy in situations were you don't want to offend anyone, but you definitely want to filter the water. I wish I'd had one of these when I lived in Mexico.
The Epic has two filters, one intended for domestic tap water, which I did not test, and one intended for outdoor use. For anything other than your home tap water, you want the outdoor filter. Using it is simple. The lid fits on any Nalgene water bottle, if you've already got one you can buy The Answer 2.0, which will fit any wide-mouth water bottle. The Epic claims to filter 75 gallons before you need to change the filter. Replacement filters are $20 when you buy two.
Specs Weight 1.6 oz. (45 g) with bottle Filtration Not disclosed Type Two-stage: Fiber layer with Carbon inner Speed ~1 liter per minute - Photograph: Adrienne So
Best for Postapocalyptic Survival
Grayl GeoPress Water Purifier & FilterI did not buy the Grayl bottle because I wanted to survive in a postapocalyptic hellscape; I wanted a water bottle so I could have a discreet water bottle in the Philippines. However, the word “discreet” does not apply to Grayl's operation. Put dirty water in the outer canister, place the internal canister on top, and press down to force the water manually through the filter. The GeoPress is basically an MSR Guardian without a lever. It’s fast—Grayl says it takes under 8 seconds to filter 24 ounces of water—but I do need to put the bottle on a level surface and use all my body weight to press it down.
The GeoPress uses electroadsorption and an activated carbon filter; it filters out pathogens, particulates, heavy metals, and odors. I like it because it’s amazingly fast and simple to operate; it’s durable enough for emergencies when camping and backpacking; and it comes with its own vessel and drink spout. My kids are also extremely picky when it comes to drinking water, so I needed something that would filter out bad smells and tastes. It also eliminates one problem that comes with the Lifestraw, which is that you have to forcibly sip the water through the filter yourself. This sucks (literally). With the Grayl, it’s self-contained in its own vessel and you can sip like a normal person. Replacement filters are also semi-reasonably priced at $30 a pop. —Adrienne So
Specs Weight 12.5 oz. (354 g) Filtration 0.2 micron Type Filters chemicals, pesticides, herbicides, heavy metals Speed 1 liter in 20 seconds
- Photograph: Amazon
Best for People Who Love Getting Really Close to Their Water
Lifestraw Personal Water FilterThe Lifestraw is alarming. No one wants to put their face near dirty water sources that you definitely shouldn’t drink from straight. When I tried it at the slough near my house, my daughter screamed, “No, Mommy, no!” The main problem with Lifestraws is that you have to use the force of your sucking to get the water through the filter, which I dislike. You also can’t use it to filter water for cooking, and your other family members will probably refuse to use it.
However, it’s extremely small, cheap, and light, and it works! It’s a decent backup option to have in your kit (I prefer a TrailShot or water treatment drops myself, but you do you). I’ve also tried the LifeStraw Sip, which looks a lot better when you put it in random water glasses, and I also use the Lifestraw Go when we visit family in the Gulf South, where my picky children would rather wither away into a husk than taste any hint of brackishness or sulfur in well water. They all work! But there’s better options. —Adrienne So
Specs Weight 1.6 oz. (45 g) Filtration 0.2 micron Type Hollow fiber membrane Speed n/a
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