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Water Purification

Mountain streams may look pristine and pure. Unfortunately from a biological standpoint they may not be. Years ago the rule of thumb was if the water source was suspect, treat it by boiling or adding chlorine or iodine. Now the general consensus seems to be that all water sources should be treated or purified. Have the streams and rivers we encounter in the mountains become more infected with biological contaminants? I'm not sure any one knows the answer, but people's awareness of the potential problems has certainly increased.

Individuals have different tolerances to water contaminates, and individual tolerances may vary over time. So the safest and surest practice is to treat all outdoor water, and in our increasingly protective society that has become the general recommendation.

Bacteria, viruses, and microorganisms that can cause a variety of unpleasant reactions in our bodies may contaminate water sources. Though most water-based problems are treatable, prevention is definitely more desirable.

The most common forms of purification are: boiling, filtering, and chemical additives.


Boiling is the simplest and the most effective, but not the most widely practiced method used by hikers because it requires building a fire or using a stove and leaves the water unpleasantly warm for immediate drinking. Boiling also does nothing to remove any particulate matter suspended in the water or chemical contamination.


Hiker's Water Filter Filters are effective at removing most biological contaminates, particulate matter, and some chemical contaminates. Filtering has the advantage of treating water for immediate consumption, but has the disadvantages of extra weight and the possibility of failure or clogging. It is a good idea when using filtering as the primary method of water treatment to carry a backup chemical treatment.

Bottle Filters

A variation on the traditional hiker's water filter is the bottle filter. They are lightweight and easy to use. There is no pump. Water is forced through the filter by squeezing the bottle as you drink. They probably aren't the best tool to purify a quantity of water for meal preparation, but work quite well to satisfy your thirst while hiking. Find a water source, fill the bottle, put the top back and you are ready to drink. Bottle Water Filter


Chemical Water Treatment Chemical treatments have the advantages of being very light weight and very effective at treating bacteria and viruses, but they will not remove particulate matter, may not destroy all the microorganisms present in the water, and require a time delay usually anywhere from 20 to 30 minutes or more before the water is ready to drink. The most common chemical water treatments are: chlorine, iodine, and oxidizing agents. With all chemical treatments the amount to add and the time to wait should be increased as the water temperature decreases and/or contamination levels increase. Also remember to loosen the cap on your water container and slosh some of the treated water onto the threads of the cap to eliminate contaminates that may be trapped there.

What I Do

I carry some form of water treatment with me when I'm hiking, but I don't always use one. If I believe the water source to be reasonably pure I will drink the water untreated. But if the water source is suspect I use either a bottle filter or some form of chemical treatment, and when using chemical treatments I adjust the dosage based on my best guess as to the potential for contamination. For cooked meals I treat the water by boiling only. Usually I take my bottle filter and a few water treatment tablets as a backup. So far this method has worked well for me, but it may not work for you. Use your own judgment based on your own experience. When in doubt treatment of some type is the safest choice.

Related Information:

Water Impurities

Chemical Purification

Water Purification Supplies:

Chemical Purification - CampSaver

Hiker's Water Filters - Altrec, CampSaver

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