Flagstaff Hikes

Sedona Hikes

Helpful Info

Finding a Water Filter

A drinking water system is basic safety equipment for any traveler or hiker. Untreated water can contain protozoa, giardia or cryptosporidium, bacterium like E. coli and other parasites. The ability to screen out viruses, size and other features will help determine the filter system that’s right for you.

Potable water describes the drinkable quality of water that has been treated to remove any harmful microorganisms. For safety’s sake, virtually any water taken from streams or lakes should be treated, or made potable, before it’s consumed. This is true whether you’re camping in a national park or canoeing in a tropical rainforest.

Waterborne Microorganisms

Protozoa are the single-cell parasitic microorganisms causing the most water-related illnesses in the United States.

Giardia, the most common protozoa, attaches to the wall of the intestine and wreaks havoc in the digestive system. Protozoa are resistant to iodine and must be removed
by filtration.

Bacteria are smaller than protozoan cysts, but no less unpleasant.
Examples of food and waterborne bacteria include

Cholera, Salmonella and E. Coli. Some bacteria are small enough to pass through a filter and must be eliminated with chemical disinfection. Virulent strains of E. coli, such as Escherichia coli, can multiply quickly in the intestinal tract. First symptoms usually begin within twelve hours of ingestion. As the infection runs its course, it may cause cramping, water loss, diarrhea and other various discomforts.

Viruses are the smallest and most dangerous water contaminants, causing life-threatening diseases such as polio and hepatitis. They are particularly a concern for water outside North America; however, they most often occur in areas with significant human contact. Small enough to fit through a filter, they must be removed by chemical disinfection.


Methods of Water Treatment

Boiling your drinking water, while less convenient, is still an
effective choice for campers. According to the Centers for Disease Control, a one- to three-minute boil (depending on altitude) will kill all known waterborne pathogens. However, boiling will not remove chemicals or reduce turbidity. Not to mention that all that extra fuel for the stove can get pretty heavy on long trips.

Chemical Disinfection is generally lightweight, inexpensive, effective and easy to use. However, without a neutralizer, the taste is strong and unpleasant. Adding a little lemonade or other powdered drink mix can help mask the taste.
Chemical purifiers, or halogens, are available in tablets, crystals or drops, and can be used to treat water for bacterial and viral contaminants. However, these may not work as well against protozoan cysts like giardia. Chemical purifiers can be time-consuming (anywhere from 15 -45 minutes to work), can be slowed even further by cold water and can be rendered ineffective by particularly murky water.
For health reasons, iodine is not recommended for prolonged use. Some people, particularly those who are pregnant, nursing or have thyroid conditions, should avoid iodine completely. However, chemical purifiers are a great pack item for back-up or emergency use.

Filtration is the most foolproof way to create potable water. A water filter blocks the passage of objects through a porous filter. Filters are ranked on a pore-efficiency rating, which roughly corresponds to the smallest object that can pass through it. A filter with a one-micron rating will eliminate most protozoa. It takes a filter with a rating of 0.2 microns to get bacteriumas well as parasites.
Some filters are more expensive than others. The cost of filters usually affects reliability, durability and longevity as well as the technology of their design. Occasional backcountry users may do fine with a less expensive model, while a more extensive trip will require a more sophisticated system.


Features to Look For

  • A minimum of 1 liter-per-minute filtering capacity
  • A handle that has good action and is sturdy
  • A pre-filter that will keep out large particulants
  • An intake hose that is fairly long
  • For backpacking, one that weighs around 20 ounces


Keep your water filter maintained and clean. All filters will eventually clog, and filter elements must be replaced according to the manufacturer’s recommendations to work properly.

Filter Usage Tips

  1. Follow manufacturer’s cleaning and maintenance instructions exactly. A little routine maintenance goes a long way in extending filter life.
  2. To avoid possible contamination, store the clean water hose in a separate plastic bag from the dirty water intake hose.
  3. Seek out the cleanest water available. Still pools contain less debris and sand than running streams. Keep the intake hose off of the bottom where it can collect mud and silt.
  4. If possible, allow water to settle out the dirt and silt. Set aside a potful of water for an hour or two (overnight if possible) before filtration.
  5. Proper long-term storage dramatically affects a filter’s life. Flush the filter element with diluted chlorine solution to kill all remaining microrganisms before storing.
Page Last Updated 4/14/02
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