BLOG 11. Purify Your Water
By Cliff Jacobson
I’m pretty lackadaisical about purifying my drinking water in the backcountry. I am, however, careful to take it from areas that are not prime sources of pollution. I follow these guidelines:
1. Don’t take water from the shoreline. On lakes, go well out from shore.
2. Avoid green-colored water. “Green” indicates the presence of algae which attract microorganisms. Water that is brownish-tan is generally okay; this color is due to natural tannin from conifer trees.
3. Avoid beaver dams and lodges, and hence, a common source of Giardia.
4. Water taken from a sun-lit pool (UV kills microbes) is usually okay. But avoid water that flows over sunny rocks because the tumbling action mixes up microbes from the bottom. Microorganisms tend to lurk just below the surface of calm water, out of reach of sunlight.
TREATING YOUR WATER
Boiling kills everything except heat-resistant spores which fortunately, are extremely rare in the Boundary Waters and beyond. Boiling won’t kill spores; a pressure cooker will! Most harmful microbes--even cryptosporidium, which can survive exposure to iodine, chlorine, and bleach--are killed by boiling (Cryptosporidium is almost non-existent in the BWCA). Just bring the water to a rolling boil and stop—the water won’t get any hotter if you continue to boil.
Filters remove microorganisms but they don’t kill them. Purifiers kill microbes but don’t remove them. Purifier-filters do both. A filter with a 4-micron pore size will stop Giardia; a one micron filter will catch cryptosporidium. If you’re going to the Boundary Waters where the water is clear and marginally safe, a 4-micron filter is probably all you need. Generally, large pores mean fast water delivery; small pores slow the flow.
Water Purifer with plastic pump. BWCA. Cr. Mike Rapatz
PUMP OR GRAVITY FLOW?
Most filters and purifiers are activated by a hand-operated plastic pump. Frankly, I’ve never had good luck with plastic pumps over the long haul, but you may fare better. Recently, I’ve been playing with the new The Platypus Gravityworks™ filter. It’s reasonably compact and lightweight (12 ounces) and it will filter a gallon of clear water in less three minutes—that’s fast! There’s no pump—gravity does all the work (just hang the unit from a tree or set it on a slope). The filter pore size of 0.2 microns will stop protozoa, bacteria and particulates, but not viruses. The unit is easy to clean (no disassembly required) and there are no mechanical parts to fail. I like that it is impossible to put dirty water into the filtered (clean) reservoir. This unit is simple and easy to use. Give it some thought if you need to filter a lot of water fast for a large group. It’s ideal for clear water lakes like those in the BWCA.
Platypus Gravityworks™ filter is simple, fast and easy. The replaceable filter backflushes easily. Water flow is very fast. It's ideal for the BWCA.
The good news is that purifiers kill just about everything. The bad news is that they do it with chemicals—generally iodine or chlorine—which imparts an unpleasant after-taste which some people can’t tolerate. A carbon filter helps, but not enough. Chemically treated water tastes bad. Period!
Halazone, Potable Aqua and Aqua-Mira are the old chemical standbys. MSR Aquatabs™ are the latest new kid on the block. Well, not really—the chemical, Sodium Dichloroisocyanurate has been used by the World Health Organization for many years. Aquatabs meet EPA purifier standards for viruses, bacteria and Giardia cysts. They have a stable five year shelf-life. Unlike typical chlorine and iodine-based tablets, Aquatabs leave little to no aftertaste. One tablet purifies two quarts of clear water. When using a micro filter you can use Aquatabs after filtering when viruses are a concern.
I laughed the first time I saw the SteriPen™--a battery operated, Magic Marker sized unit which kills microorganisms with ultraviolet light. I wondered, does this thing really work? I figured its pricey UV bulb would break before I finished my canoe trip. Hardly! My SteriPen is seven years old now. It has followed me to Costa Rica, Norway and the high Arctic and has never let me down. It purifies a liter of clear water in about 90 seconds without the use of chemicals. There is no after-taste and no hoses or pumps to work or untangle. I can operate it in the middle of a lake from the seat of my bobbing canoe. It is by far my favorite purifier.
SteriPen™, my favorite.
TRUST THE SCIENCE
I know people who own, but don’t trust, their water purification system. Some of them are my close friends. They pack their purifier away and fill their canoe with jugs of water they bring from home. I bring a lightweight water bottle and SteriPen™. I’ve never had a problem. The treated water that purifiers—and most filters produce—generally exceeds the quality of most commercial bottled water and tap water. Trust the science. This stuff works!