Know H2O: How to Purify Drinking Water

By author of Brow Tines and Backstrap

Knowing how to make water safe to drink is a crucial backwoods skill

Treating water before consuming it can prevent a plethora of illnesses. (Bill Konway photo)

You’re way off the grid on a wilderness elk or mulie hunt, and you've run out of water. You find a creek. You're thirsty. But is it free of disease and safe to drink? If you don't purify it, chances are that it isn't. You can only survive about three days without water. Knowing how to purify it is a good skill for anyone to master, but a must for people who spend time in the outdoors. 

It’s best to purify any water that you drink outdoors, regardless of the source. But some water sources present lower risks of contamination. These sources include underground sources, freshly fallen precipitation, dew and some plant-based sources. Lakes, ponds, rivers, creeks, streams, flood water and puddles all have higher risks of being contaminated due to their static environment.


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Countless parasites and illnesses can be contracted from drinking water that hasn’t been purified beforehand. According to the Centers for Disease Control and Prevention (CDC), some of the contaminants you may encounter in bad water include Salmonella, Guinea Worms, Giardiasis, Schistosomiasis, Legionella, Cryptosporidiosis, Amebiasis, Campylobacter, E. coli, Enterovirus, Hepatitis A, Norovirus, Rotavirus, Shigella, and more.

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Always keep at least two water-treatment methods on hand. (Shutterstock / Timothy Epp photo)

Purification Methods

Drinking water that hasn’t been purified isn’t worth the many risks that accompany it, especially when there are so many effective ways to purify it. Try these methods below. Your gut will thank you.

1. Boiling

Boiling can kill most pathogens in water, and it is the most effective means of purification. That said, it doesn't remove metals or pollutants. To use this method, build a small- to medium-sized fire that is 1 to 2 feet in diameter. Then, fill a pot with your soon-to-be drinking water and set it over the open flame.

Heat the water until it boils (heavily) for at least five to six minutes. Some sources recommend boiling water as long as 30 minutes. However, according to the CDC, at altitudes greater than 6,500 feet, boiling your water for at least three to four minutes should do the trick. Once finished, strain the water if possible, and pour the purified water into sanitized containers and continue boiling as much water as you can carry. This will save you time — and potentially your life if you get in a pinch or water sources are scarce — since you already have a fire started.

2. Distilling

Distilling water is time-consuming and not as efficient as boiling, but still a good option for removing bacteria and viruses. To do this, use a distillation system that purifies water by heating it and collecting water vapor as it changes back to a liquid from a gas. You lose water volume in the finished product with this method, but it's still effective.

The bad news? Some toxins found in heavily polluted water evaporate at the same temperature as H2O. So, don't use this method when purifying water from sources near big agricultural areas, cities or developed areas. This method is best for water sources with lower risks of toxicity.

There are many different shapes and styles of distillers. But the simplest versions include these basic components:

  • A container (with lid) to heat water in
  • An approved hose for water vapor to rise and travel through
  • A container for water vapor to collect in and convert back into liquid water
  • Seals and gaskets

Choose the most effective, yet compact, system you can buy (or build).

3. Filtering Straws and Water Filters

Situation depending, you might not be able to carry a pot or distilling system into the backcountry. You might not be able to start a fire. So, you need a backup plan. Straws that filter out diseases and other contaminants work. Some of the best on the market include the LifeStraw, Sawyer Mini and NDuR straws. My personal favorite is the LifeStraw. It’s compact enough to fit neatly in my pack. It's not a primary purification source, but it provides added security and confidence during a week-long hunt.

As for larger water filters, these come in many different shapes and sizes. Choose one small enough to take with you. As for functionality, most filters are designed to use a carbon- and ceramic-based build to cleanse the water.

4. Ultra-Violet Bulbs

The ultra-violet route is viable for removing bacteria. Insert an ultra-violet bulb into the water and allow it to run for the allotted time before drinking. Different models work at different speeds. Read the labeling to be sure. Solar-based purification is another option, similar to ultra-violet bulbs in functionality, but it's not exactly practical in the backcountry.

5. Purification Tablets

Many back-country hunters carry these. They should kill most (if not all) bacteria, parasites and viruses found in the water. Simply drop the tablet in, and wait for the amount of time listed on the label. Different tablets have different procedures.

The bad news? Tablets sometimes leave a rough taste in your mouth. They also do not remove chemicals, sediments or heavy metals. Most are either chlorine- or iodine-based. (Note: iodine options can pose health risks to people with certain diseases, conditions, and women who are pregnant.) As with all purification methods, read directions carefully and fully understand proper use before adding them to a big cup of creek water.

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