Once upon a time, you didn’t need such a newfangled contraption as a backpacking water filter. Getting a refreshing drink meant dipping your tin Sierra cup (or Nalgene) in any stream and taking a nice, cool, clear drink. The good news is that if you can find a spring, that still works. Unfortunately, the water most of us encounter backpacking may well contain giardia and other fun protozoa and bacteria that can quickly ruin your trip.
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 complicated to operate than dipping a cup in a stream. In fact, our first two picks allow you to do pretty much that, drinking clean, cool water almost straight from a stream.
Once you’ve purified your water, I recommend making a nice hot cup of coffee on one of our top-pick backpacking stoves. Don’t forget to check out the rest of our outdoor buying guides, including the Best Base Layers, Best Backpacking Tents, Best Merino Wool, and Best Puffer Jackets.
Updated July 2026: I’ve added a new section at the bottom to highlight some more filters I’ve tested. I’ve also added further testing notes after another season with our top two picks, and updated links and prices throughout.
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, which is the size of the pores in the filter element.
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 (which are too small for most filters). 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. You can combine a filter with a chemical method if you want to remove sediment and deal with viruses.
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 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 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 directions 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 freezing temps in spring or fall, make sure you bring your filter to bed and keep it in your sleeping bag with you overnight.
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Best for Ultralight Hikers and Backpackers
Photograph: Scott Gilbertson
Sawyer
Squeeze Water Filter
A 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 of 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 ($27). This setup allows me to get two liters of clean drinking water in about four minutes if I squeeze, and more like six to eight minutes 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 a Sawyer Mini ($17) that 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 -
Best for Simplicity and Convenience
Photograph: Scott Gilbertson
Katadyn
BeFree Water Filter
The 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 in 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 from 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
