by Michael Hodgson

With a quality water filter, you'll zap backcountry micro-cooties before they can cramp your style.

Water-dwelling micro-cooties never cease to hit below the belt, and clear mountain water is no guarantee of purity. When you're in the backcountry you have to treat water before you drink it.

Filters — The First Line of Defense

PUR Water Filter

Filters are compact, light, and easier to use than ever. A decent filter can be bought for less than a week's supply of Pepto-Bismol and antibiotics.  The goal of a filter is to rid your drinking water of microscopic contaminants, rendering water clear and reasonably pure. How well your filter does this depends on the filter's pore size efficiency. A filter with a rating of one micron or smaller will remove protozoa such as giardia and cryptosporidium, as well as parasite eggs and larvae. It takes a pore-size efficiency of less than 0.2 microns to remove harmful bacteria.

Eliminating Viruses

Knocking out viruses, however, is another story. They're so tough that experts are now urging recreationists to take virus-prevention measures anywhere in the world — not just in developing countries or other places with, shall we say, questionable septic methods. Until recently, that meant getting a filter that incorporated iodine or packing a bottle of iodine tablets. First Need is one filter that claims to meet EPA virus-removal standards by filtration alone — a nice change from the yucky taste (and for some, the health risks) of iodine. Most antiviral filters involve an iodine element; when its job is done, a carbon element rids your water of any face-scrunching aftertaste.

The Word on Carbon

Carbon also reduces the presence of such chemicals as pesticides, herbicides, heavy metals, and chlorine, but take heed: A few recent studies have shown that in certain situations, it's best to give the iodine time to do its job. If your water source could possibly be contaminated with sewage, remove the carbon filter and let the iodine sit in the water for 15 to 20 minutes. You can then add ascorbic acid crystals to make iodine residue more pleasing to the palate. In addition, when a carbon element reaches its limit, the gnarly stuff slips through. Always replace the filter cartridge and the carbon element according to the manufacturer's recommended schedule.

A Few Must-Haves

A filter worthy of backcountry use should weigh less than 20 ounces, be easy to grasp, simple to operate, and a cinch to clean and maintain.

Regardless of where you'll be drinking, always buy a water filter that removes protozoa and bacteria. A number of cheap, pocketsize filters remove only giardia and cryptosporidium and pose a risk to your health for the sake of saving a few dollars. Be sure to check the flow rate of the filter you're considering. It shouldn't be slower than a liter per minute.

Use and Anti-Abuse

All filters clog — it means they've been doing their job. Do not force water through a filter that's becoming difficult to pump; you risk injecting a dose of microscopic nasties into your bottle. Some filter models can be backwashed or scrubbed to extend their useful lives. If the filter has a prefilter to screen out the big stuff, use it. It'll up your filter's capacity by as much as 100 gallons per disposable element. Finally, each filter has its own idiosyncrasies and care needs, so read the instructions before using.

Purifying Options

Boiling

Once considered the only safe way to purify water, the cost and hassle of carrying fuel, setting up the stove, and then waiting for the water to cool makes this option rather impractical. For those set on boiling their way to crystal spring water, times have changed since the old school recommended 10 minutes of rolling boil. It is now generally acknowledged that just bringing the water to a rolling boil will kill giardia. Still, 10 to 15 minutes of rolling boil is the only way to kill the many other "heat resistant" waterborne pathogens, and that takes lots of time and fuel.

Chemical Treatments

Given enough time to work, both iodine and chlorine are effective means of killing (although not removing) bacteria, viruses, and microorganic parasites. But therein lies the often-confusing issue: How much time is enough? pH concentration, particulate matter, and water temperature are all variables that can hinder a chemical's ability to effectively treat water impurities. Chemical treatments will not remove dirt, algae, or chemical contaminants and are often inhibited by them. Murky water filled with silt and other organic matter should first be strained, thereby improving the chemical's ability to actually do its job — purify.

Beyond the somewhat odiferous quality and unique taste of iodine, a taste that leaves most users scrambling for the Wylers, pregnant women and individuals with thyroid problems should not drink water treated with iodine without first getting a doctor's approval, as it is a potential health risk. Iodine, ingested over long periods of time and in enough quantity, is considered toxic. This shouldn't pose too much of a worry for the periodic weekend warrior; however, those traveling into the backcountry on a regular basis and relying on iodine exclusively may want to rethink the risk.

Chlorine

Chlorine is not considered a toxic chemical by itself, however studies have shown that when combined with certain organic chemicals, carcinogenic byproducts can be formed. Chlorine hasn't been proven effective against amoebic cysts, something many travelers abroad worry about. In temperatures of greater than 80°F (not uncommon in any trunk or garage), chlorine crystals or tablets have a very limited shelf life. Chlorine's effectiveness deteriorates quickly once exposed to air.

About the author
Michael Hodgson, author of Camping for Dummies and The Day Hiker's Handbook, has written extensively about hiking, camping, paddling, climbing, and the gear you need to do it all. You can contact him at www.adventurenetwork.com.