How to Purify Water While Hiking

Camping & HIking Expert Kate Wilson breaks down the difference between water purifiers and water filters and shares the best ones to bring on your next adventure.

Photo by Kate Wilson

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When I first started hiking +20 years ago, it was in the desert near Las Vegas, of all places. I would fill the Camelbak to the brim and limit myself to small sips of water along the trail to ensure there was enough to last the entire hike. As the trails grew longer I almost certainly ran out of clean water every time, especially in the summer months.

Those hot, dry adventures were a good lesson in planning for hydration needs but after a few trips outside of the desert, I learned that carrying a water filtration system nearly eliminates the need to limit my intake. Today, I own three that are used regularly depending on the circumstance, and the question I love to answer most as a Curated Expert is: “Are water filters necessary?” Yes. Pretty much.

Not only do they allow you to refill a bottle or hydration bladder from natural springs, creeks, or lakes, many solve the problem of water tasting dirty or having sediment. They also lighten your load overall since you won’t be carrying large quantities of water on the trail. Most importantly though, filters are effective in providing safety from viruses, contaminants, or any natural water source where bacteria is a concern.

It Looks Clear, So I’m Safe, Right?

Unfortunately even crystal clear, flowing water can make you sick. As a rule, unless there is a risk of dehydration, I never drink water that hasn’t been filtered. The consequences of doing so can vary from minimal diarrhea to extreme illness or even death!

Giardia is of considerable concern; it’s a parasitic protozoan (one-celled animal) that derives from animal or human feces, thrives in cold, clear water, and will reproduce itself in your intestines. This causes extreme dehydration, dizziness, and the inability to think straight—all dangerous conditions when you’re out in the wilderness. My partner was immobilized after contracting Giardia from contaminated water. Fortunately, he made it to the hospital for antibiotics but still talks about the agony of that experience today!

Cryptosporidium is another common waterborne parasite that’s very easily transmitted and also survives for long periods of time in cold water. There is no antibiotic treatment for the infection this critter causes though; your body just has to get rid of it on its own after days or weeks of diarrhea, cramps, and fever.

Listed below are several ways in which you can avoid these and other illnesses caused by contaminated water.

Purifiers Vs. Filters

The author's MSR and Platypus water filters are bagged and laying on soft green moss and young leaves next to a creek.

Photo by Kate Wilson

What is the difference, and which one is suitable for your needs?

A filter strains out common U.S. and Canadian protozoan cysts like the two mentioned above, as well as bacteria like Salmonella and E. coli. A purifier does the same, and also fights Rotavirus, Norovirus, and Hepatitis A—viruses that are too small for filters to catch. You would want a purifier when spending time overseas in less-developed parts of the world.

Purifiers

Fortunately, there are modern solutions that minimize the risk of drinking from even the most questionable water sources. A popular, trusted purifier is the Grayl Geopress. It is highly rated for its removal of waterborne pathogens (viruses, bacteria, and protozoan cysts) as well as the ability to filter out pesticides, chemicals, heavy metals, and microplastics. It also improves the taste/smell and gets rid of sediment from even the dirtiest water sources in as little as 8 seconds. Relatively inexpensive with incredible reviews, this is a top choice if you have a little extra room in your pack for the 24-ounce bottle and especially if you are traveling overseas where the water contains more bacteria and risk than we come across in the states.

Product image of the Grayl Geopress Water Purifier.

Grayl Geopress Water Purifier

A more lightweight, packable option for purifying water in any location is water purification tablets or drops. Katadyn Micopur MP1 Purification Tablets are used worldwide by travelers and backpackers for eliminating all microorganisms including cryptosporidium, bacteria, viruses, and for improving the overall taste and smell. They do require more time—about 4 hours for the chlorine dioxide to kill cryptosporidium—and do not remove particles or ‘floaties’ from your water so they are best paired with a filtration system if possible. Otherwise, this type of purification is a no-brainer since it fits in your pack easily and is relatively inexpensive.

The SteriPen Adventurer Opti UV Water Purifier is yet another solution, offering a quicker water purification system than tablets. Swish this ultraviolet light pen into 0.5-1 liter of water for 48-90 seconds, respectively, to eliminate bacteria, protozoa, and viruses. It runs on lightweight batteries (included) that purify 50L of water, and the pen doubles as an LED flashlight too! Weighing just over 3.5 ounces, this UV light purifier is an awesome choice for backpackers, although again, it does not filter sediment or particles.

Filters

The author's partner pumps water into their water bottle with the MSR Miniworks EX filter as they squat on a log crossing a creek.

MSR Miniworks EX. Photo by Kate Wilson

There are many options to filter water when hiking in areas where you don’t have to be quite as concerned about viruses. High alpine lakes and streams generally offer clear water sources that are less risky when consumed after filtering. My top pick is the MSR Miniworks EX pump filter because it filters without chemicals and in general, is a hiker’s dream! It removes 99.9% of protozoa and 99.9999% of bacteria from beginning to end of the filter life in ‘worst-case’ water. It also improves taste and smell, eliminating chemicals, toxins, and even sediment/particles with its ceramic and carbon filter. This filter has a flow rate of 1 liter per minute, can be cleaned/maintained in the field and at 1 lb is a solid choice for backpackers.

The award-winning MSR Guardian Purifier is a step up if you’re wanting to eliminate viruses as well. Designed for military squads and used globally for viral protection, it may just be the ultimate water filter system—especially since it also only weighs 1 lb!

There are preferred types of water filters; below are the other options available and the pros and cons of each from either personal experience or top customer reviews.

Lightweight

Many thru-hikers are ever concerned with the weight of their pack and are happy to share their reviews of the best backpacking water filters:

Katadyn BeFree

Product image of the Katadyn - BeFree 0.6L Filtration System.

Katadyn BeFree Filtration System

The Katadyn BeFree system is a light, collapsible bottle that works immediately! Simply fill the reservoir, screw on the filter, and drink—no waiting required! Rated highly for its weight, packability, and treatment time.

  • Pros: Immediate treatment, easy to use, fast flow rate, collapsible, lightweight, and comes in 0.6, 1.0, or 3.0-liter sizes.
  • Cons: Lower rating for the durability of the pouch itself.
  • Effective against: Particulates, protozoa, and bacteria.
  • Weight: 2.1 oz.

Sawyer Micro Squeeze

Product image of the Sawyer Micro Squeeze Water Filter and its components.

Sawyer Micro Squeeze Water Filter

The Sawyer Micro Squeeze filtration kit is another solid choice for backpackers, weighing in at just 2 ounces. It effectively eliminates the usual water contamination suspects as well as 100% of microplastics, which have been found in over 80% of water samples. Exposure to these tiny particles can cause toxicity, inflammatory lesions, and increased cancer risk, so this little filter may be one you want to use with bottled and tap water, too! All Sawyer Squeeze filters are adaptable, meaning they don’t just fit the included 32 oz pouch but also many water bottles, hydration reservoirs, and even faucets. Additional purchase of adapters for these connections may be required at a minimal cost.

  • Pros: Lightweight, packable, and affordable personal filter system with multiple attachment options.
  • Cons: Flow rate relies solely on sucking force and is slow to get going, especially with the hydration bladder attachment. The filter clogs easily (but is maintainable in the field!).
  • Effective against: Particulates, protozoa, and bacteria.
  • Weight: 3.8 oz.

Convenient

I think most hikers will agree—convenience is king out on the trail. Pumping, squeezing, or waiting are not the top three things on our list of enjoyment. I recently learned about inline filters, and based on stellar reviews I will be getting one soon! The concept just makes sense: click the filter into any hydration bladder, which then doubles as a gravity system, and you’re ready to go!

MSR Thru-Link

Product image of the MSR Thru Link Inline Filter.

MSR Thru Link Inline Filter

The MSR Thru-Link filter uses hollow fiber technology and activated carbon to provide safe, clean-tasting water with minimal weight added to your pack!

  • Pros: Inexpensive, convenient, and lightweight.
  • Cons: Awkward quick attach connector allows water to spill out when the hose is disconnected. Not recommended for water that is silty or muddy.
  • Effective against: Particulates, protozoa, bacteria, chemicals, and toxins.
  • Weight: 2.5 ounces.

LifeStraw

The author's LifeStraw is arranged half in and half out of the water to show how it works.

LifeStraw Personal Water Filter. Photo by Kate Wilson

The LifeStraw is also incredibly convenient in that you use it to drink directly from natural water sources. I’ve used mine in some sketchy backcountry streams in a pinch and always carry one with me for emergencies. No filling of bottles or pouches, pumping, or waiting is required. Super lightweight and reliable, it’s a good filter to have as a backup and at $20 there is no reason not to!

  • Pros: Ultralight, takes up no room in the pack, inexpensive, and easy to use!
  • Cons: Not designed to take water with you on the trail since you drink straight from the straw.
  • Effective against: Particles, protozoa, and bacteria.
  • Weight: 1.7 oz.

At Camp

Platypus GravityWorks

The author's Platypus GravityWorks system hanging from a tree with their campground set up in the background.

Platypus GravityWorks. Photo by Kate Wilson

We have used this gravity filter system and found it to be the optimal solution for water at camp after a long hike. Simply fill the ‘dirty’ bag, hang it from the nearest tree, and within minutes you have between 2-6 liters (up to 1.5 gallons of water) filtered into the ‘clean’ bag without pumping or squeezing. Great for larger groups!

The Platypus is compatible with water bottles, hydration bladders, and can even be converted into a hand washing station.

  • Pros: Great for filtering large quantities of water, plus it packs down small and fits in your backpack pouches. We bought ours for packrafting and it’s been great (if you don’t mind holding the bag high for a few minutes!).
  • Cons: Top closure can be finicky and the filter slows down with high amounts of particles—we did find this to be true.
  • Effective against: Particulates, bacteria, protozoa.
  • Weight: 11.5 oz.

Of course, if you are at camp and have the gear to do so, boiling your water is just as effective and convenient as any method mentioned above (with the exception of filtering out sediment). Bring to a rolling boil for one minute, or three if you’re at elevations above 6,500 feet, and destroy disease-causing organisms like viruses, bacteria, and parasites.

So there you have it—some effective and convenient ways to make sure you stay safely hydrated on the trail, in the backcountry, or at camp. Looking for a filtration system for your next adventure? Chat with me or another expert for a customized recommendation!

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20+ years of camping, mountain biking, winter sports, climbing, fly fishing, backpacking, hiking and traveling - there's no place I'd rather be than outside. Here are my favorites (so far!) ​ CAMPING: Blue Mountains, Australia. HIKING: Mt Cook or Nelson, New Zealand MOUNTAIN BIKE: Moab, of course! F...

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