When was the last time you knelt in the soft grass of a pristine alpine meadow and sipped cool, clear water directly from a high mountain stream?
It’s a delightful feeling, but one that’s increasingly rare for cautious hikers who don’t enjoy explosive diarrhea (so, all of us?). Sipping water from the wrong stream — one with cattle grazing upriver, or too many humans camping nearby — can lead to Giardia or worse.
Fortunately, it’s never been easier to filter water while backpacking. Filters keep getting smaller, lighter, and cheaper, and there’s no reason not to use one whenever you hit the trail.
What’s the best way to filter water while backpacking? The market may seem crowded, but the most experienced backpackers gravitate to the same handful of tried and tested solutions. The ideal backpacking water filter is lightweight, efficient, effective, and affordable, and there just aren’t that many that make the cut.
In this article I’ll cut through the fluff and present the actual best water filters for backpacking, according to the most experienced backpackers and thru hikers. I’ll also tell you which water filters have worked well for me personally during the thousands of miles I’ve thru hiked and backpacked, and which haven’t.
Nasty Waterborne Pathogens
First, let’s quickly review the types of little buggers we’re trying to protect ourselves from.
On small screens, this table scrolls left and right.
|Parasites / Protozoa
|E. Coli, Salmonella, Cholera
|Hepatitis A, Norovirus, Polio
|0.2 – 5 microns
|1 – 15 microns (relatively big)
|0.02 – 0.3 microns (relatively small)
|Removed by filters?
|Removed by purifiers?
|Killed by chemical treatments?
|Found in water in developed countries?
|Tap water: no
Natural water: sometimes
|Tap water: no
Natural water: sometimes
|Tap water: no
Natural water: rarely
|Found in water in developing countries?
|Tap water: sometimes
Natural water: sometimes
|Tap water: sometimes
Natural water: sometimes
|Tap water: sometimes
Natural water: sometimes
The most common problem caused by all of these: diarrhea and other digestive upset, ranging from mild to catastrophic. In rare cases, viruses can be fatal (for example, Polio is still a problem in some parts of the world) though travel immunizations offer protection.
How do these buggers get into the water? Usually through the poop of infected people or animals. In the US, cattle and human campers (both of which poop in the woods) are common causes of contamination even in remote areas.
Hiking + Travel: Consider a Purifier
First, an important note for those who like to combine hiking with travel or who live outside the “developed world”: you might need a purifier for backpacking, not a filter, and yes there is a difference.
Filters work by physically straining out larger bad stuff – bacteria and parasites – with tiny pores. They don’t protect against viruses though, which are small enough to slip through.
Purifiers use an additional method like chemical or ultraviolet treatment to deal with viruses in addition to bacteria and parasites, making even the dirtiest water sources safe to drink.
The filters discussed in this post are appropriate for most backcountry hiking in more developed areas of the world where tap water is considered safe to drink. If you travel or live in places where sanitation infrastructure isn’t developed enough to keep human waste out of the water supply, you’ll face additional threats in both tap and natural water that filters alone do not protect against (namely, viruses).
Very rarely, popular recreation sites in the US have been involved in virus outbreaks. If drinking from a lake with a lot of human activity nearby, consider a water purifier or treat your filtered water with chlorine dioxide to be extra safe.
Since most hikers reading this post will be looking for filters, not purifiers, I won’t cover purifiers for backpacking here. See my guide to water purification for travel if you’re looking for a purifier.
Best Backpacking Water Filters
While traipsing around the US on the Colorado Trail, Arizona Trail, John Muir Trail, and more, I’ve noticed the same several water filters used by almost everyone. These filters are popular because they work! Here are the gold standards of backpacking water filters as of 2023.
The Sawyer Squeeze (and its variations) might well be the most popular water filter among backpackers, and for good reason. I’ve been using it for years with great results and think it’s an excellent water filter for backpacking.
There are three models of Sawyer filter: the original Squeeze, the smaller Mini, and the smallest Micro. Flow rate decreases with size and clogging becomes more likely. For especially dirty water sources like those common in the American Southwest, I recommend the largest Squeeze model to avoid clogging. For clear mountain streams the smaller Mini or Micro work well. All models need to be backflushed periodically (easy to do) to keep them flowing well.
All the Sawyer filters have a flexible setup. Use with a squeeze bag (though I highly recommend replacing the included pouch with a CNOC bag), attach to a hydration bladder hose with a connector kit (either for filtering into the bladder, or inline filtering as you drink), connect to a Smartwater bottle, or set up as a gravity filter with a CNOC dirty bag.
Best for: individuals, or groups if used with a CNOC bag as a gravity filter.
The Katadyn BeFree is similar to the Sawyer, but not quite as flexible with its setup. You can squeeze filter into another container if you want, but the BeFree is really designed to be used with a soft bottle as an inline filter. It can also be set up as a gravity filter using a bigger bag, like the Katadyn 3 liter gravity bag.
It’s not compatible with the ubiquitous Smartwater bottles loved by thru hikers, though the collapsible Vesica bottle does come in a compatible version.
The BeFree is cleaned by swishing instead of backflushing, which is easier but also less effective if the filter gets clogged. I’ve heard it has a very fast flow rate out of the box but slows significantly with use and can be hard to clean, so it’s recommended only for clear water sources. On the plus side the filter itself is very compact.
Best for: individuals or groups.
If you’re hiking in a group and want a convenient shared solution, the Platypus GravityWorks filters 4 liters of water at a time. It’s a bit bulkier because it includes its own clean bag instead of integrating with your bottle or hydration bladder. It’s also more expensive.
I’ve found the flow rate is good, it’s easy to backflush, and it doesn’t clog easily, making it a very convenient solution. My husband and I used to share a GravityWorks before I began taking more solo adventures and switched to a Sawyer; now we each carry our own personal water filter for more flexibility. But if you want the best large-volume gravity filter for backpacking, the GravityWorks gets my vote.
Best for: groups
Gravity versus Squeeze Filters
This is a matter of what pushes the water through the filter: gravity, or you. All these filters can be considered “squeeze” or “gravity,” depending on how you configure them and whether you hang them up on a tree (or a hiking pole tripod) or squeeze the bag.
I prefer the convenience of a gravity water filter for backpacking so I can do other things – setup camp, eat lunch, etc. – while my water filters itself. But if you’re only filtering a liter or two at a time and packing really light, you might prefer the weight savings and compactness of a more minimal squeeze pouch.
Drawbacks of Hollow Fiber Filters
All three of the above filters use hollow fiber technology. These types of filters are easily damaged by freezing or impact, so you’ll need to take good care of them.
If there’s any chance the temperature is near freezing, carry the filter cartridge in your pocket and sleep with it at night. Protect them from hard impacts too. If you think there’s a chance the filter is compromised, you shouldn’t use it. It’s surprisingly easy for this to happen, so have a backup plan like chlorine dioxide drops or sharing a friend’s filter.
Hollow fiber filters gradually clog over time, and no amount of backflushing or swishing will return them to their original flow rate. If you backpack a lot you can expect to replace your filter cartridge from time to time, potentially even in the middle of a long thru hike.
Other Water Treatment Methods
Chlorine dioxide is a chemical treatment, not a filter, but it has a similar effect. It kills all bacteria and viruses and most protozoa, though it takes four hours to be effective against hard-shelled Cryptosporidium. Most backpackers are not going to carry water they can’t drink for four hours.
Is Cryptosporidium a risk? It definitely can be, even in the US. It’s most common in areas with high contamination from human and cattle. In more remote places you can probably take your chances.
Chlorine dioxide is a good ultralight water treatment option in areas without Crypto risk, and ideally with clear water sources (unlike a filter, it won’t help with harmless but unappetizing particulates). This is especially true for short trips, otherwise you’ll need to carry a lot of it.
It also works well as a lightweight emergency backup in case your primary filter fails, or as a second step to purify extra-nasty water that’s already been filtered.
UV treatment tools like the SteriPen are technically purifiers not filters (they’re effective against viruses too), but I’m including it for completeness because a small minority of backpackers prefer them.
The SteriPen is a battery-powered device that purifies a bottle’s worth of water at a time. They are fast and easy, but can be awkward for treating large amounts of water in multi-liter hydration packs. They also have the potential to fail or run out of battery.
Most importantly for backcountry applications, they’re not effective in cloudy water; they neither remove the gross particulates nor kill pathogens effectively. I would definitely not use a SteriPen on trails with lots of murky water, such as many in the American southwest.
Water Filters NOT Recommended For Backpacking
Unless you have a special reason to prefer one of these options, I don’t recommend them for backpacking.
Pump Filter – No
My very first backcountry water filter was a pump filter. They are excellent for getting water from shallow sources where a bag is hard to fill, can be more resistant to clogging, and some provide purification too. They will also balance out all that hiking with a good upper body workout!
There are a few good pump filters, such as the MSR Miniworks, but I prefer the hands-off convenience of a gravity filter system. Pumps also tend to be bigger, heavier, and more expensive. I almost never see backpackers using pump filters anymore, especially the lightweight and thru hiker types.
Bottle Filter – No
Despite the large number available, I don’t see serious backpackers using hard-sided filter bottles. Though convenient for a single bottle’s worth of water, they’re inconvenient for filling a larger hydration bladder and they’re heavy as far as bottles go. Save your water bottle filter for travel or camping.
Straw Filter – No
Like bottle filters, I’m not sure what the best use case is for straw filters in the backcountry. Most don’t connect with bottles or bladders, so they only allow you to drink when actually at a water source instead of taking water with you. I know basically no one who manages water this way while hiking.
They also seem redundant. A cartridge from a gravity or squeeze filter could be used as a straw filter if needed, while being far more versatile. They might make a reasonable backup, but chlorine dioxide tabs are cheaper and smaller.
Iodine and Chlorine – No
Unlike chlorine dioxide, these types of chemical water treatment drops don’t work against cryptosporidium at all. They’re also less effective against Giardia, which is very common, and iodine can have negative health impact if used long-term. If you’re going to use a chemical treatment, use chlorine dioxide instead.
My Personal Picks
I’ve listed a lot of options here, and they all have their own advantages. It can be hard to choose!
For those in search of a quick answer, here are the water filter systems I personally use for backpacking and thru hiking.
Sawyer Squeeze Filter: My recommended water filter for backpacking in the American southwest, such as Arizona and New Mexico, where you’ll be drinking from very dirty sources. I choose the Squeeze over the smaller Mini or Micro models in this case because it doesn’t clog as easily. Example: Arizona Trail, parts of the Colorado Trail.
Sawyer Mini Filter: My recommended filter for mountains or anywhere the water is likely to be clear. I choose the Mini over the Micro because it’s not much heavier and seems less likely to clog over time. Examples: John Muir Trail, Tahoe Rim Trail.
Aquamira Chlorine Dioxide drops: My recommended treatment for short, fast, and light hikes in places with clear water. Example: Mineral King Loop.
Sawyer Squeeze + Aquamira Drops: My recommended purification method for extra-nasty water or sources near populated areas, or when backpacking in another country with questionable water quality. Examples: parts of the Arizona Trail, Congo Nile Trail in Rwanda, hiking from Guinea to Senegal.
Do you really need to filter?
It’s your hike, your choice, potentially your explosive diarrhea. The general consensus from the outdoor community is definitely yes, you should filter or treat your water.
I filter or chemically treat all my backcountry water and would recommend you do the same. These days you can buy an effective ultralight water filter for less than $40! Gone are the days of pumping for what feels like hours while your fingers freeze and your camp dinner gets cold.
If you like living on the edge, you might choose to not filter your water in some very specific places. Since contamination comes from animal and human excrement washing into water sources, choose places with almost no chance of humans or animals upstream or uphill. Very high elevation streams in very remote places may qualify.
Other Water Contaminants
Other than bacteria, parasites, and viruses, here are a few other contaminants you may need to consider in special cases.
Toxic algae: A growing concern in parts of the United States, cyanobacteria (blue-green algae) produces cyanotoxins that are released into the water when the spores rupture. These toxins can be fatal. Though filters remove the spores themselves, they don’t remove toxins that have already been released into the water. Purification methods like boiling, chemical treatment, and UV light don’t either. An activated carbon filter within a purifier, or added as a second step after filtration, seems to be the only way to remove some but not all of these toxins.
Heavy metals: In areas with a history of mining, surface water in creeks and lakes can contain unhealthy concentrations of heavy metals. I’ve encountered a few places in Colorado, for example, where locals warned me not to drink from the streams. Activated carbon filters are the best defense against heavy metals, or you can just plan ahead to avoid filling up in these areas.
Microplastics: I’m honestly not clear on how common these tiny pieces of plastic are in natural water sources, or whether they’re a problem. But since the smallest microplastics are around 2 microns (1.6 according to Wikipedia) which is larger than many bacteria, any standard water filter should filter them out.
When choosing a water filter for backpacking or thru hiking, here are some other aspects to think about:
Shared or individual: Larger capacity gravity filters are convenient when hiking in a pair or group, but only if you intend to meet up at every water refill. If there’s a chance you’ll want more independence (“Meet you at the top of the climb in a few hours”) then it’s nice for everyone to have their own water filter. It’s also usually faster to filter in parallel, and a nice backup in case one person’s filter fails.
Large amounts of water: In hot or dry climates you may need to filter 4 or more liters at a time. Choose a treatment method that’s fast, won’t run out like chemical treatment, and won’t drive you crazy like pumping or squeezing. Gravity setups are great for this case.
Compatible with your water containers: Do you prefer to carry water in a hydration bladder, Smartwater bottle, or something else? Whatever you use, make sure it interfaces easily with your filter setup.
Flexible water capacity: On a long hike it’s common to have a few sections that are much drier than others, so it’s nice to have expandable water capacity. This might mean buying extra disposable bottles or carrying a collapsible bottle or bladder. A nice advantage of gravity filters is that the dirty bag can be used as extra water capacity when needed.
Hard-to-fill-from sources: Ever tried to fill up a filter bag from a slow trickle or shallow puddle? Containers with wide openings make this easier, or you can use a cup or pot as a scoop. For the tiniest of trickles, try engineering a leaf spout to create a dripping faucet.
Weight and style of travel: Gear weight and size matter more to some folks than others. Consider how much you value saving weight, time, energy, and money as you choose your water treatment method. Usually you can only optimize a couple of those aspects at a time.
Backup methods: Filters can easily break, freeze, or get lost. I’ve even had chlorine dioxide bottles crack and spill! You can roll the dice and drink untreated water in an emergency and deal with the consequences later, but it might be unpleasant or even dangerous. I think chlorine dioxide makes a great lightweight backup option to get you to civilization if needed.
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Or, visit the backpacking resources center for the full list!
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