Photo: Jim Meyers/TandemStock

How To Choose the Best Backcountry Water Treatment Methods and Tools

There are several technologies available, all with their own pros, cons, and best uses.

That backcountry stream may look pristine, but don’t be fooled—water in the wilderness might be hiding invisible pathogens capable of giving you a nasty gastrointestinal infection. Whether the germs come from wildlife, agriculture, or other hikers’ unsanitary bathroom habits, the result is the same: an unfortunate ending to your trip. Dodge this fate and ensure clean drinking water with a safe and effective backcountry water treatment method. There are several technologies available, all with their own pros, cons, and best uses. Here’s how to choose the right one for you.

In this article, you’ll learn:

  • Which backcountry pathogens to be concerned about
  • How and when to use pump filters, gravity filters, squeeze and bottle filters, and straw filters
  • How and when to use ultraviolet and chemical treatments
  • Why boiling isn’t an efficient purification method

What's in the Water?

Gastrointestinal distress can come courtesy of several different pathogens, but the symptoms are generally the same: abdominal cramping, diarrhea, fever, and vomiting. There are three main suspects. Bacteria, such as E.coli or campylobacter, tend to get into the water supply from other humans. Protozoa, like giardia and cryptosporidium, are parasites that live in water between hosts. Viruses, such as Hepatitis A or norovirus, are primarily a problem in developing countries, not the U.S. or Canada.

Treatment #1: Filters

Water filters work by forcing water through a filtration element with tiny pores. The element physically removes bacteria and protozoan cysts, allowing clean water to flow through. Most filters don’t remove viruses because they’re much smaller than other pathogens (a few do have the ability to deal with them using additional purification measures). Many require you to periodically replace the element, and silty water can clog them. Filters come in a variety of shapes and sizes, from single-serving bottles to group-size pouches.

Pump Filters

These devices include a hose that goes into the water source, a hand pump to force water through the element, and an outflow that adds clean water to your bottle or reservoir. 

Pros: Can treat large volumes of water relatively quickly; can pull from shallow or small water sources

Cons: On the heavy/bulky side; can break in the field; require manual pumping

Best For: Backpacking; groups

Gravity Filters

Fill this filter’s large, flexible water pouch and hang it up, then watch as gravity forces the water through the element for you.

Pros: Simple; require little effort; can treat large volumes of water

Cons: Work slowly; can be hard to fill from shallow water sources

Best For: Backpacking; groups

Bottle and Squeeze Filters

To use this personal-size filter style, fill the bottle or reservoir with water, then force it through the element by squeezing, sipping through an integrated straw, or pressing it coffee-style. 

Pros: Small; lightweight; simple; work quickly; more affordable

Cons: Don’t treat large volumes efficiently

Best For: Day hikes; trail running; backpacking in areas with plentiful water; ultralighters

Straw Filters

These ultralight, simple filters let you sip water directly from the water source.

Pros: Very small; very lightweight; more affordable

Cons: Don’t treat large volumes efficiently; require you to get down on your stomach to drink

Best For: Day hiking; trail running; ultralighters; emergency use

PLUS: Purifying filters

A few specialized filters do neutralize viruses as well as bacteria and protozoa, either through the addition of chemicals or a high-tech ion exchange process. They work well anywhere in the world, but some are expensive.

Treatment #2: Ultraviolet Light

These devices work by zapping water with UV light, thereby damaging any pathogens’ DNA and rendering them unable to infect you. They work best in clear water because germs can “hide” behind tiny particles in cloudy or silty water. UV devices work on bacteria, protozoa, and viruses.

Pros: Quick; simple; lightweight; some are rechargeable

Cons: Don’t treat large volumes of water efficiently; more expensive

Best For: Day hiking; backpacking; international use

Treatment #3: Chemicals

Certain chemicals kill all pathogens, including viruses. Just add the drops or tablets to your bottle or reservoir and wait for the chemicals to work their magic (usually 30 minutes to 4 hours for certain pathogens). The most common chemical treatment is chlorine dioxide. Iodine is an old-school solution that also works, but has its cons: It tastes weird, doesn’t work on crypto, and isn’t safe for pregnant women or those with thyroid conditions.

Pros: Very small; very lightweight; very affordable

Cons: Take a long time; can add an unpleasant taste 

Best For: Backpacking; ultralighters; emergency use

What About Boiling?

It’s true: Boiling backcountry water will also take care of all pathogens. But you’ll have to pack enough extra fuel to handle all your drinking water needs, and this method also requires you to wait for water to cool before drinking. Water treatment methods are quicker and more convenient. One circumstance where boiling does work well: cooking. No need to pretreat the water you’ll use to cook your rice or pasta—just bring it to a rolling boil first.

All articles are for general informational purposes.  Each individual’s needs, preferences, goals and abilities may vary.  Be sure to obtain all appropriate training, expert supervision and/or medical advice before engaging in strenuous or potentially hazardous activity.