Drink Up—How to Purify Water in the Backcountry

Words and photos by James Roh

Purifying water in the backcountry is like doing your taxes—an inglorious but necessary task. Sure, you could not do either, but eventually your negligence will catch up to you in a big way. When planning a trip, it’s nice to think that where you’re headed is so pristine that you can just drink straight from the stream, as if the water is as pure as the mountain air. Unfortunately, that’s rarely, if ever, the case and a fact that we adventurers have to accept and deal with. But with the right tools, it’s not as laborious as it sounds.

Knowing your three microorganism enemies—parasites, bacteria, and viruses—is the first step. Some of the more famous single-celled parasites are cryptosporidium and giardia, mostly because they’re so prevalent. In order for the water to be fully potable, those little creatures have to be killed, and, broadly speaking, this is possible by utilizing heat, filtration plus chemicals, chemicals alone, or UV light. Each method comes with its own set of advantages and disadvantages. These same techniques can also be used when traveling to developing nations where there is often a lack of infrastructure to prevent contamination or to adequately treat water for human consumption.

“Purifying water in the backcountry is like doing your taxes—an inglorious but necessary task. Sure, you could not do either, but eventually your negligence will catch up to you in a big way.”


Boiling water is a simple and reliable method that uses heat to kill the microorganisms. A rolling boil for a minute is adequate, but if you’re at altitude (above 6,500ft) it’s recommended to let it boil for up to three minutes, as water boils at lower temperatures higher up. While boiling water is pretty straightforward, it is also very fuel intensive and a Nalgene of hot water isn’t always enticing after a long day of hiking. Neither is taking the time to let it cool down. If going with this method, it is imperative that your stove is very fuel efficient, or you carry a lot of fuel.

Chemical Additives

Chemical additions, whether in liquid or tablet form, are fairly common with backpackers and utilize different chemicals to disinfect water, primarily chlorine or iodine. Each chemical is offered in several different preparations with varying degrees of success. Key benefits to chemical disinfection systems include low weight, packability, and they are often inexpensive. The disadvantages include no organic matter filtration, possible ineffectiveness in cloudy, contaminated, or cold water, and a chemical taste. The biggest emphasis is to follow the manufacturers’ instructions carefully when employing this method.


Microfiltration is a common water treatment method used in the backcountry. Pump, gravity, and even straw versions exist, but all perform the same function. They remove organic material and sediment from water sources that are encountered in the wilderness, such as rivers, lakes, and glacial streams. This is an especially attractive option when the water source looks questionable, such as desert rivers or stagnant water. The water is further filtered through a porous filter that prevents many microorganisms from getting through. These fine filters can be ceramic (fragile but smaller pore size) or fiberglass (more convenient but bigger pore size). Most filters are capable of removing organisms three microns or bigger. However, some bacteria, such as cholera and E. coli, are smaller. Therefore, to be 100% potable, filter manufacturers suggest adding chemicals to the filtered water. A SteriPEN (see below) is also very effective in this scenario. Just make sure you’re well versed in cleaning it so you don’t get hampered by a clogged filter in the middle of the nowhere.

How to purify and treat water in the backcountry.
Pump your way to clean, drinkable water.

After years of using filters in the backcountry, the Katadyn Hiker Pro has easily become my favorite. Once you get it set up, it works fairly seamlessly. Like other filters though, it can get clogged up, which is understandable. What separates the Hiker Pro from other leading brand filters is how easy it is to clean. Instead of carefully scratching a very fragile ceramic filter, the Hiker Pro utilizes a pleated fiberglass filter cartridge that you can just unfold and wipe down with a sponge or cloth. Plus, you can plug the output hose straight into your hydration bladder without even taking it out of your pack.

Ultraviolet Purification

SteriPEN are the wizards of the backcountry. Simply press a button and insert a glowing wand into your water bottle for a minute or so and you have perfectly drinkable water. Sound sketchy? Yep, I thought so too, but the scientific evidence is there and, after using it for several months in Nepal, I’m a believer. The ultraviolet light emitted from the device destroys all microorganisms it comes in contact with, all in under two minutes. The only major caveat is that the SteriPEN isn’t effective in cloudy or murky water and it chews through batteries, so keep that in mind. For me, the SteriPEN is especially useful when traveling internationally. Just be prepared for funny looks from those who have never seen one in action before.

How to purify and treat water in the backcountry.
The SteriPEN’s UV glow lights up the night as it makes water safe to drink.

Regardless of the method you choose for your adventure, I strongly encourage having a backup in case your pump breaks, batteries die, tablets are broken, or you run out of fuel. In general, it’s a good idea to have backup chemicals since they’re cheap and so lightweight. Waterborne illnesses make for a miserable experience. Trust me, I’ve been there.