Every product is carefully selected by our editors. If you buy from a link, we may earn a commission.

A Pro’s Guide to Water Treatment in the Wild

Outdoor survivalists often teach the rough rule of three’s: humans can only survive three minutes without oxygen, three hours without proper shelter (given extreme conditions), and three days without water. H2O is the most suspect of the bunch.


Outdoor survivalists often teach the rough rule of three’s: humans can only survive three minutes without oxygen, three hours without proper shelter (given extreme conditions), and three days without water. Though oxygen is likely a given on land, and warm, water-resistant clothing can suffice as shelter in a short-term survival scenario, natural water is the most suspect of the bunch. Regardless of how clean or clear it appears, unseen contaminants are likely lurking beneath the surface. Which is why survival expert Ted Smith, a senior instructor at the REI Outdoor School with decades of knowledge and experience in outdoor education, recommends arming yourself first with some basic knowledge: how and where to collect water, and the difference between the two main types of water treatment, filtration and purification. We worked with Smith to gather the insight and know-how for each method, and discussed the proper gear to help you stay hydrated when it’s needed most.

MORE OUTDOOR STORIES: Guide to Camp Stoves | Guide to Survival Gear | Best Hiking Shoes of 2014


Inside the U.S. and Canada

Filters are the first line of defense in water treatment. The process is purely physical, whereby water is strained through pore-sized openings leaving bacteria and protozoa behind (note: this method does not remove viruses). Made of either charcoal, glass, or ceramic, most filters on the market work sufficiently, differing in performance of speed of filtration, the user’s energy expenditure, and durability. Though water sources in developing countries should be met with extra caution (see: purification), filtration is often adequate treatment for water sourced from lakes and rivers inside the U.S. and Canada.

Gravity Filters


Expert Advice: “My go-to for a group of any size. It’s lightweight, fast, and dependable. You can also be doing other things while it filters on its own.”
Pro: Filters large quantities of water quickly with little effort. Compacts nicely when not in use and can also attach to reservoir systems such as CamelBaks.
Con: Hard to use with smaller water sources.
GP Recommends: Platypus Gravityworks Water Filter 4L System

Buy Now: $120

Ceramic Filter


Expert Advice: “Tried and true. Ceramic filters are great for their consistency, though you may have to earn your drink with some labor.”
Pro: Consistent for the individual user.
Con: Easy to break and requires routine maintenance if used with frequency. Requires effort and attention to use — not for groups.
GP Recommends: MSR MiniWorks EX Water Filter

Buy Now: $90

Squeeze Filters


Expert Advice: “Essentially a gravity filter without gravity. Ultralight for the solo backpacker and does well when water sources are plentiful.”
Pro: Lightweight and compact.
Con: Not good for groups, or transferring water to other containers.
GP Recommends: Sawyer Squeeze Water Filter

Buy Now: $40

Tips for Smarter Sourcing

It’s always best to source natural water from a moving body (such a flowing river or stream). The rocks and debris act as a natural filter to remove some of the gunk and murkiness attributed to stagnant water sources. In conjunction, setting up camp should be influenced by your proximity to water. However, keep in mind that water is attractive to other animals as well, including predators. You want to be close enough that sourcing is convenient, but not too close that you become a target.


The Virus Killers

The main difference between filters and purifiers is that the latter also treats viruses (i.e. hepatitis A, rotavirus, enterovirus, norovirus) most often present by human and animal fecal matter. The traditional method of water purification is achieved by boiling. But because this requires both time and energy, it’s now often reserved as a last resort in light of chemical purification, which is easier and more efficient. The two main methods of purification in the backcountry are dissolving iodine tablets to water reservoirs and introducing ultraviolet (UV) light. Though neither method will remove the foreign contaminants, they do prevent these from multiplying, rendering them safe for the human body.

Pen Purifier (UV Light)


Expert Advice: “I have buddies that swear by this, though I have seen inconsistent results. Can also be tedious if you are filling up multiple liter bottles or a reservoir.”
Pro: Quick, lightweight, and kills viruses without changing the taste of water.
Con: Yields inconsistent results.
GP Recommends: SteriPEN Adventurer Opti Water Purifier

Buy Now: $90

Potable Aqua Iodine Tablets + Neutralizer


Expert Advice: “This can be used as your primary method of treating water or as a great backup in a survival kit. The neutralizer helps mask the taste of the iodine, but isn’t necessary; I sometimes use sports drink mix. Always remember to follow instruction and wait the 30 minutes before you drink.”
Pro: Lightweight and foolproof.
Con: Limited number of tablets for groups or long trip.
GP Recommends: Potable Aqua Iodine and Taste-Neutralizer Tablets

Buy Now: $11

To learn more: The REI Outdoor School offers more than 50 classes per year in each of the co-op’s larger communities. Field instructors have completed a minimum of 40 hours of professional training through the REI Outdoor School Field Instructor Training Program and are experts in the activities they teach. Wilderness Survival covers practical tips and strategies that every outdoor traveler should know, including: emergency priorities; how to make an emergency shelter; how to locate and access drinking water; and how to make your own emergency kit with all the essentials.

Advertisement - Continue Reading Below
More From Outdoors