Regardless of how clear and clean the fresh mountain stream burbling past your campsite may look, don’t drink it without treating it.
Microscopic pathogens in your water are invisible to the naked eye, but they still cause diarrhea, cramps, vomiting, and fever. And those are just one example of the dangers lurking in your untreated backcountry waterbottle.
There are three types of waterborn cooties that will make you sick: small protozoan cysts, like cryptosporidium, smaller bacteria, like E. coli, and smallest viruses, like hepatitis A—usually not a concern in North American water, but a danger for international travelers. All get into your water from feces.
Water may also contain chemicals you don’t want to drink, like fertilizer residues, or visible organic matter—dirt, tannins, silt—which might make rehydrating less than pleasant.
Use common sense when selecting your water source—steer clear of heavy agriculture, opt for a moving source, and get as far away from human and animal activity as you can get.
Fortunately there are many ways to kill microorganisms in your water, remove or break down chemicals, and strain off detritus. Here’s our handy how-to guide to cleaning up your drink: