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Water Purification

Most authorities recommend that you boil, filter, or chemically treat all water taken from a questionable source. That’s sound advice, providing you have the necessary chemicals and/or equipment plus the self-discipline to use them. Although I occasionally boil (160 degrees will kill almost everything) my drinking water on backcountry trips, I confess to laziness in this respect. As often as not, I drink untreated water, but I am very careful where I get it. Here are the guidelines I religiously follow:

  • Go well away from shore to get your drinking water. If you are camping at a spot that is frequented by humans or animals, go upstream of the source to get your water. On lakes a minimum of 150 feet from shore is recommended.

  • Decay organisms (bacteria and protozoans) generally prefer the shallows, so the deeper your water source, the better. On large lakes I often weight a cooking pot with a rock and let it down 30 feet or more by rope. Avoid any water that has a green or greenish brown color. Water with a green tinge contains algae and is usually loaded with microorganisms.

  • Don’t take water from backwaters and stagnant areas. These are breeding places for microbes.

  • Don’t take water near beaver dams or lodges. Beavers are the favored host of Giardia lamblia— a small protozoan that will make you plenty sick!

  • Filters and Purifiers

    Filters strain out microorganisms, but they don’t kill them. The critters are just trapped and held inside the filter. Eventually, the filter loads up (water flow decreases), and you have to clean or replace it. Filter pore size is the nemesis of all filtration units. Pores small enough to trap the tiniest microbes impede water flow and pumping efficiency; large pores let more water through— and possibly some dangerous germs too!

    Purifiers kill microbes with chemicals, but they don’t filter them out.

    Enter the purifier/filter. It has moderately sized pores that allow a fast flow rate, plus a chemical that kills microbes that pass through the filter. The downside is an often chemical aftertaste that can be reduced (but not entirely eliminated) with a final carbon filter.


    From the book Canoeing & Camping Beyond the Basics, 3rd, by Cliff Jacobson. Copyright © 2007 by Cliff Jacobson. Used by permission of FalconGuides, a division of Globe Pequot Press. Visit

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