Having some form of water treatment, and knowing how to use it is essential when hiking. Not only can untreated water taste foul, but it also can be loaded with waterborne pathogens that'll make you so sick you'll have to pause your hike or even stop it completely.
In this post, you will learn how to choose a water filter so that you can drink water from streams, ponds and puddles without risking your health. In fact, these are the very filtration systems used by thousands of thru-hikers who have to survive days, weeks and sometimes even months at a time in the wilderness without access to a potable water source.
Let's start by looking at when and where water filters are a necessity.
Purification vs. Filtration
What's the Difference?
Filtering and purifying water are used interchangeably, but the two processes are very different. Filtration is used to remove bacteria and protozoa from water, while purification removes everything, including viruses. Knowing the difference between the two is critical so you can purchase the correct product and avoid contracting a waterborne illness.
Filtration is used to remove bacteria and protozoa from water. As you filter your water, those pathogens get caught in the tiny filter membranes. As we'll explain below, bacteria and protozoans are not life-threatening but are damaging enough to keep you off the trail for a few days, or even a few weeks.
Purification goes one step further than filtration by removing viruses as well as bacteria and protozoa from water. Purification is a bit more complicated than filtration as it is usually a longer process. However, treating water for viruses in areas with poor sanitation can save you from contracting serious diseases like meningitis, polio or hepatitis A or E.
Note: Not all filters are created equal. Some pump filters, like the MSR Guardian, both filter and purify water thanks to medical-grade filters that are much finer than what you'd find in a squeeze filter, for example.
Which Do You Need?
To sum up the difference between filtration and purification, purification removes viruses, whereas most filters don't. So when it comes to choosing the right system for your hike, you need to understand whether you are at risk for viruses where you're going to be.
Backcountry water sources in the US and Canada are relatively clean, unless they are in an area that is highly contaminated with human or animal waste. So as a general rule of thumb, hikers in these areas will only need to filter their water, not purify it. On the other hand, if you are visiting a less-developed country like India or Nepal, then a water purifier is a must-have.
The Steripen Ultra is a UV purification system that uses light to destroy pathogens.
Common Types of Water Filters (and Methods)
SQUEEZE FILTERS AND GRAVITY FILTERS: THE POPULAR CHOICE
With filtration, you collect your water in a small pouch or water bottle and attach your filter by screwing it onto the end of the vessel. You then squeeze the bottle or pouch to push the water through the filter.
You can also hang it upside down and let gravity pull the water through the filter. It only takes a minute or two to fill your water bottle with fresh, clean water. Because they are lightweight and easy to use, filters are a popular choice among backpackers.
WATER PUMPS: THE HEAVY DUTY SOLUTION
These filtration units use a pump to force water through a small-pore filter membrane (0.02 micron or smaller). They have a tube that you place in your contaminated water source and a pump handle that you squeeze to filter the water into a clean water bottle. Most pump filters have replaceable filters that need to be cleaned regularly and changed when they are so gummed up they can no longer be cleaned.
CHEMICAL: A GOOD BACKUP PLAN - SLOW, BUT COMPACT AND LIGHTWEIGHT
The most common purification method is chemical. It is popular because it is portable, easy to use and less likely to fail when you need it the most. You only have to carry around two small vials of chemicals or a handful of small tablets. As long as the chemicals have not expired, they work effectively to destroy the bacteria, protozoa, and viruses. You simply add the chemicals and wait for them to work.
The chemical reactions take time, so you must treat your water before you need to drink it. Depending on the type of chemicals you use, you may have to wait up to four hours before you can drink your water. Not everyone likes chemical purification as some of the chemicals used to sanitize your water can give it an off-taste. It also takes longer to work as temperatures decline. Because of these drawbacks, many long-distance hikers carry a filter to treat their water and use chemicals as a backup in case their filter fails.
UV: THE SYSTEM THAT ALSO WORKS IN COLDER WEATHER
Another popular purification method is UV sterilization, which uses a wand with a UV light source to scramble the DNA of bacteria, protozoa, and viruses. You place the wand in your water source, turn it on and stir for a minute or two. It's quick and doesn't change the taste of your water. Because it uses light, you need to carry batteries or a portable charger to keep it powered though. Unlike chemical purification, UV purification still works even when it is cold out. You do need to pre-filter the water to remove any particulates as it loses its effectiveness when the water is turbid.
BOILING: IF ALL ELSE FAILS - REQUIRES TIME AND FUEL
Boiling is another method that is effective at killing bacteria, protozoa, and viruses in water. It doesn't change the taste of the water and doesn't require battery power, but it does take time. You should bring your water to a rolling boil and boil it for at least one minute. At altitudes higher than 6,562 feet (2000 meters), you should boil your water for 3 minutes. You do have to make sure you have enough fuel for your stove to boil all the water you plan to use for drinking or cooking. Because of the cost and weight of carrying extra fuel, most hikers use boiling as a backup in case their primary method fails.
With the MSR Guardian, you can pump clean water directly into your Nalgene.
Considerations
Not all water purifiers are created the same. Some require prep time, some take time to filter, and some even require batteries. Below, we breakdown the significant features you need to consider before deciding which filter to buy for backcountry adventures.
PREP TIME: FROM A FEW SECONDS TO SEVERAL HOURS
Not every purification method delivers potable water in an instant. Some filters require assembly or priming before they can produce clean water, while chemical processes require time to neutralize pathogens. Make sure you know how long your method takes and plan appropriately.
TASTE AND ODORS: CLEAN DOES NOT MEAN ENJOYABLE
Some filtration and purification methods can remove tastes and smells, but most do not. In fact, some chemical purification methods, like iodine, add an unpleasant taste to the water. If you don't like the taste of your water, you can always add a drink mix packet to cover it up. Note most natural stream and spring water tastes phenomenal though! It's oftentimes those stagnant and dirty water sources that can have a strange taste.
LIFE SPAN: DISPOSABLE VS REUSABLE FILTERS
Most filters have a maximum amount of water that it can filter before it needs to be replaced. You will often see this advertised as the number of gallons the filter can handle. The Sawyer MINI, for example, can filter up to 100,000 gallons before you need to replace it. Most filtration units are disposable. Once you reach their limit, you need to replace the entire unit. Some, like the MSR Guardian, ship with replaceable filters.
FLOW RATE: MORE TIME WAITING = LESS TIME HIKING
Flow rate measures the amount of water that can pass through a filter. The faster the flow rate, the faster you can filter your water. There is nothing worse than a slow flow rate filter that seems to take forever to filter.
Chemical treatment takes time but remains a very lightweight and effective way to purify water.
WEIGHT: 2 OUNCES MAY BE ALL YOU NEED
Look for the lightest weight filter or chemical set that'll do the job. Not everyone needs the pumping power of an MSR Guardian and can do just fine with the compact Sawyer Micro or Katadyn BeFree. If you go with a battery-activated water purification system, like the Katadyn Steripen Ultra, be sure to factor in the weight of the batteries, as those are usually sold separately and not accounted for in the product weight you see advertised on a brand's website.
PORTABILITY: TABLETS < FILTERS < PUMPS
Bring what you need for your trip, but don't overpack. Most filtration units and chemical treatments are pocketable and take up minimal space in your backpack. If you are going into an area that has heavily contaminated water, then you may have to sacrifice some space to get a larger and more robust pump filter like the MSR Guardian.
COMPATIBILITY: CHOOSE A FILTER THAT MATCHES THE REST OF YOUR GEAR
Filtration units often ship with a bag or pouch that you use to gather water. The filter then screws onto the container, and you squeeze it to force the water through the filter. Some filtration units are designed to fit inline with a hydration bladder or attach to a refillable plastic water bottle. Make sure you purchase a filter that is compatible with your current hydration system.
MAINTENANCE: BACKWASHING AND FREEZING TEMPERATURES
Most filters require you to backwash them after each use. Backwashing removes any particles that stick to the pores of the filtration membrane. If you don't backwash regularly, you may clog your filter and significantly reduce its lifespan. You also need to protect your filter from freezing conditions as ice crystals will put holes in the filter membrane. When temperatures fall below freezing, you should carry your filtration unit near your body during the day and in your sleeping bag at night.
Squeeze filters are instant.
Simply fill up your water container at the source and squeeze clean water out.
Best Water Filters for Backpacking
| Model | Bateria | Protozoa | Viruses | Prep Time | Life Span | Type | Weight | Price |
|---|---|---|---|---|---|---|---|---|
| Sawyer Squeeze | ☑ | ☑ | ☐ | Instant | Lifetime | Squeeze | 3 oz | $35 |
| Sawyer MINI | ☑ | ☑ | ☐ | Instant | 100k gal. | Squeeze | 2 oz | $20 |
| Sawyer Micro Squeeze | ☑ | ☑ | ☐ | Instant | 100k gal. | Squeeze | 2 oz | $29 |
| Katadyn BeFree | ☑ | ☑ | ☐ | Instant | 264 gal. | Squeeze | 2 oz | $45 |
| Katadyn Steripen Ultra | ☑ | ☑ | ☑ | 90 sec. | 8,000 uses | UV | 5 oz | $109 |
| Hydroblu Versa Flow | ☑ | ☑ | ☐ | Instant | 100k gal. | Squeze | 2.6 oz | $20 |
| Aquamira Water Treatment Drops | ☑ | ☑ | ☑ | 30 min. | 30 gal. | Chemical | 3 oz | $15 |
| Potable Aqua Water Germicidal Tablets | ☑ | ☑ | ☑ | 4 hrs | 8 gal. | Chemical | 0.28 oz | $17 |
| MSR Guardian | ☑ | ☑ | ☑ | Instant | 2,600 gal. | Pump | 17.3 oz | $349 |
| MSR Trail Shot | ☑ | ☑ | ☐ | Instant | 528 gal. | Squeeze | 5.2 oz | $50 |
Sawyer Squeeze
Prep time: Instant
Life span: Lifetime (warranty)
Type: Squeeze
Weight: 3 ounces
Price: $34.95
Effective Against: Bacteria and protozoa
The largest of the three Sawyer filters, the Squeeze is the top choice for its filtration speed. It filters water at 1.7 liters per min, allowing you to fill a water bottle in less than a minute. This fast filling is a huge bonus when you want to get your water quickly and get back on the trail. The Squeeze includes pouches for collecting water, but that is not necessarily a benefit. The bags have a narrow mouth and are difficult to fill, especially in streams or pools of water that are shallow. We had to use a bottle or cup to fill the pouch with water, which was inconvenient.
Sawyer MINI
Prep time: Instant
Life span: 100,000 filtered gallons of water
Type: Squeeze
Weight: 2 ounces
Price: $19.95
Effective Against: Bacteria and protozoa
The Sawyer MINI hits the sweet spot on affordability with a price tag just under $20. It's also lightweight, weighing a mere 2 ounces. Like Sawyer's other filters, the MINI performs quickly and reliably. As long as we were careful to backwash, it never failed in our testing. Our biggest gripe is its slower flow rate. After using the Sawyer Squeeze and Micro, it is hard to go back to the slower MINI. If you are looking for a filter to use only occasionally or as a backup, the MINI is a great choice, but thru-hikers who will be filtering a lot of water will be better served by the faster Sawyer Squeeze or Micro.
Sawyer Micro Squeeze
Prep time: Instant
Life span: up to 100,000 gallons
Type: Squeeze
Weight: 2 ounces
Price: $28.99
Effective Against: Bacteria and protozoa
The Micro is the latest addition to the Sawyer lineup, and it is a winner in our books. It is compact, lighter, and more affordable than the full-sized Sawyer Squeeze. It is so lightweight that it is comparable to the Sawyer MINI, but it has one significant advantage over the MINI - its flow rate. We loved the rapid flow rate and the compact size of the Micro so much that it is our favorite among the Sawyer filters. It also is versatile as the other Sawyer filters. We used it with the included pouches, on a water bottle, and within a hydration system. Because it unscrews quickly, we could switch between filtering from a pouch and drinking from a bottle without missing a beat. When we were done filtering, the Micro is so lightweight we couldn't even tell it was in our pack. Sawyer improved the filter but left the pouches the same. We recommend ditching the included pouches and swapping them out for a compatible CNOC Vecto reservoir.
Katadyn BeFree
Prep time: Instant
Life span: 264 gallons (or 1,000 L)
Type: Squeeze
Weight: 2 ounces
Price: $44.95
Effective Against: Bacteria and protozoa
The Katadyn BeFree is the fastest squeeze water filter on our list. When filled to capacity, the BeFree filtered 0.6L liter in 25 seconds flat. It also was the easiest to clean - just shake it vigorously for about 30 seconds. The entire unit is ultralightweight, adding only 2 ounces to your base weight.
The BeFree uses a soft flask from Hydropack that has a wide 43mm mouth. This wide mouth and flexible construction make it easy to fill the container at water sources. It also means you cannot simply replace the flask with a water bottle if you accidentally puncture it. You have to find a flask or bottle with this larger mouth which can be challenging in the backcountry. This is a significant concern as the flask portion is made from a very lightweight material that can fail if you are not careful.
We tested the 0.6L version and found it to be a tad small for hikes that don't have abundant water sources. We drank through the 0.6 liters very quickly and wished we had the 1.0-liter version. We also wish the bottle had a loop to attach it to a backpack. Though you can stuff the full flask in any pocket, it will begin to bend and droop as you empty it. It can, and will, fall out of your pocket without you knowing.
Katadyn Steripen Ultra
Prep time: 90 seconds
Life span: 8,000 activations
Type: UV
Weight: 5 ounces
Price: $109
Effective Against: Bacteria, protozoa and viruses
The Steripen Ultra was our favorite water purifier because of its convenience and effectiveness. You literally stick the probe into your water bottle, turn it on and stir. There is an LCD display that tracks the time and takes the guesswork out of the sterilization process. You can eliminate not only bacteria and protozoa but also viruses in as little as 90 seconds. Unlike chemical treatments, there is no funny aftertaste.
Most of the time, we purified the water directly from the source because it was from a clean stream. On one occasion, we collected water from a puddle and had to pre-filter it through a bandana to remove organic material. Organics and other suspended solids interfere with the UV and reduce the effectiveness of the sterilization process.
As easy and effective as the Steripen is, it has a few drawbacks. The probe will only fit into a wide mouth bottle, so we were forced to ditch our Smartwater bottle and carry a heavier Nalgene. It also uses a rechargeable battery, and won't operate when it is low. You need to bring a charging cable and power source, which adds even more weight to your pack. Then there is the cost. Because of its electronics, the Steripen is priced over $100 and is one of the more expensive options on our list.
Hydroblu Versa Flow
Prep time: Instant
Life span: 100,000 gallons
Type: Squeeze
Weight: 2.6 ounces
Price: $19.95
Effective Against: Bacteria and protozoa
At first glance, the Hydroblu Versa Flow looks like a dual-threaded Sawyer MINI, but the differences end there. When it comes to filtering speed, the Versa Flow outperforms the Sawyer MINI with a faster flow rate that lets you filter 1.5 liters in about a minute. It's comparable to the full-sized Sawyer Squeeze and Micro, lagging only behind the blazing Katadyn BeFree. Both threads on the Versa Flow connect to standard 28mm water bottles and reservoirs.
The dual threads add versatility to the filtration system allowing you to use the filter with a hydration bladder, in a gravity filtration system, or directly on a water bottle. Each end includes a small end cap that prevents the filter from leaking inside your pack and keeps dirt and grime out of the filter.
Keeping the filter clean ensures optimal performance, and the Versa Flow makes that easy with an inspection window located on the side of the filter. The window allows you to see when the filter needs to be backwashed. It takes the guesswork out of cleaning and extends the lifetime of the filter.
Not only is the Hydroblu Versa Flow fast and easy to maintain, but it also is affordable. Some hikers balk at paying $30 for a Sawyer filter, but even the stingiest of backpackers are willing to drop $20 to get a Versa Flow. A fast filter that is easy to maintain and costs less than a meal out in town - what more could you want?
Aquamira Water Treatment Drops
Prep time: 30 minutes
Life span: 30 gallons
Type: Chemical
Weight: 3 ounces
Price: $14.99
Effective Against: Bacteria, protozoa and viruses
Aquamira is the gold standard for chemical purification and for a good reason. It takes 30 minutes to destroy bacteria, protozoans, and viruses and hardly ever fails. Because it uses chlorine dioxide, it also only adds a hint of a taste to your water. It's relatively affordable, too, with a price tag of $15 for 30 gallons of treatment.
Aquamira quickly became a staple in our backpack because it is so easy to use. It ships in two bottles - the part A solution and the part B solution. You need to mix these solutions, wait until it turns yellow and then add it to your water bottle. You must wait for approximately 30 minutes for sterilization, but the time goes by quickly when you are hiking. The two vials together weigh a total of three ounces, but you can trim their weight by carrying just the amount you will need for your trip.
Potable Aqua Water Germicidal Tablets
Prep time: 35 minutes
Life span: 8 gallons (or 30 liters)
Type: Chemical
Weight: 0.28 ounces
Price: $16.99
Effective Against: Bacteria, protozoa and viruses
Potable Aqua is the absolute lightest form of water purification you can bring on the trail. A package that can treat up to 30 liters of water weighs a mere 0.21 ounces. Potable Aqua also is the easiest to use. You simply open the blister pack, drop in a tablet, and wait for the chlorine dioxide to do its magic. The waiting period was the biggest drawback to the Potable Aqua. Each treatment takes thirty five minutes, which is considerably longer than, say, a squeeze or pump filter.
Just like Aquamira, Potable Aqua does not leave an aftertaste. We drank the treated water right from the bottle without having to add any flavoring. Though we pre-filtered any turbid water, we found that Potable Aqua often removed some of the residual organics by causing them to fall out of suspension. The water was more clear after the treatment cycle.
MSR Guardian
Prep time: Instant
Life span: 2,600 gallons (10,000 L)
Type: Pump
Weight: 1 lb. 1.3 oz
Price: $349
Effective Against: Bacteria, protozoa and viruses
When you are traveling to an area where there is contaminated water, then you want the best filter money can buy, and that filter is the MSR Guardian. The Guardian is a powerhouse pump filter that can remove viruses, bacteria, protozoa, and even particulates from 2.5 liters of water in 60 seconds flat. The pump requires you to submerge a pre-filter into the water source and then use the pump handle to draw the water through the filter. Our team found it intuitive and easy to operatae.
The Guardian not only filters the water, but it also backwashes the filter automatically with each stroke. We appreciated being able to filter turbid water without having to worry about cleaning the filter after each use. If the filter gets clogged over time, you can easily replace it.
Our biggest gripe with the MSR Guardian is the filter outlet, which fits on a Nalgene bottle or similar sized vessel. You can use it with other containers, but you cannot get a secure fit and run the risk of picking up contaminants as you filter. We also found that the filter leaked occasionally from the bottom and realized we had accidentally over-tightened the filter base. There is a small cutout that needs to be aligned to prevent the leak. Lastly, the Guardian is the bulkiest filter on our list. It takes up a lot of room in your pack, so make sure you really need it.
MSR Trail Shot
Prep time: Instant
Life span: 528 gallons (or 2,000 liters)
Type: Squeeze
Weight: 5.2 ounces
Price: $49.95
Effective Against: Bacteria and protozoa
The MSR TrailShot is a versatile filter that takes the best parts of a pump filter and packages in a squeeze-filter style packaging. It filters almost as fast as the Sawyer Squeeze, filling a full 1-liter bottle in just under a minute. It's a durable system that can handle backcountry adventures without failing. Just make sure your hands are in shape as squeezing the bulb of the filter can be tiring when you need to filter more than a liter at a time.
The winning feature of the TrailShot is its long hose that let's collect water from even the smallest puddles. In a pinch, we filtered water from rainwater that had accumulated in a depression on the solid rock face of a bald summit. No other filter, except the MS Guardian, could have harvested this water. As an added benefit, the hose has a mesh that functions as a pre-filter to remove suspended solids from clogging the filter. The TrailShot also is easy to clean. Just like the Kataydn BeFree, you only have to shake the TrailShot to clean the filter and restore the flow rate.
The output end of the TrailShot ends at a small spout. You can drink directly from the spout or point the spout so you can filter water into any sized container. It also can be connected inline with an MSR Trail Base kit to create a gravity filter.
The MSR Trail Shot lets you squeeze water straight from the source into your container.
What Pathogens to Watch Out For?
Water-borne pathogens can be broken down into three major categories - bacteria, protozoans, and viruses.
BACTERIA
Bacteria commonly found in water, especially in North America, include Escherichia coli (E. coli), Salmonella, Campylobacter, and Shigella. Common bacteria are not very serious. Symptoms usually include diarrhea, stomach cramps and sometimes vomiting as well as fever. Enough to get you off the trail for a week or two.
PROTOZOANS
Protozoans include Cryptosporidium and Giardia. Similarly to the bacteria mentioned above, these micro-organisms will cause stomach infections that will manifest in the form of diarrhea and stomach pains. The infection usually clears up within two weeks, sometimes more.
VIRUSES
Viruses found in contaminated water include hepatitis A, rotavirus, and norovirus. Water-borne viruses are rare in North America; they're more commonly found in areas with poor water sanitation and can lead to a wide range of infections that take several months to heal up. Heptatis A, for example, is a liver infection whose symptoms can last up to 6 months and include extreme tiredness, loss of appetite, dark urine and yellowing of the skin and eyes. On the other hand, the effects of norovirus (commonly referred to as "food poisoning" or "stomach flu"), usually wear off within a few days.
The Katadyn BeFree is water filter that doubles as a water container. Fill it up and drink up.
Which Water Sources to Filter From?
You'll encounter a variety of water sources on the trail that range from murky swamps to fast-flowing streams. The best water sources are clear and fast flowing. Avoid stagnant water sources which tend to accumulate algae and other particulates. These floaties will clog your filter and taste nasty when you drink them.
If your only water source is turbid, then you should pre-filter the water through a bandana or a t-shirt to remove large particulates. If you don't have any clothing to spare, then you can use sphagnum moss or sand packed into a soda bottle. You also may want to have a cup or extra bottle handy to help scoop out the water from a shallow stream.
650-Calorie Fuel