How to Purify Water
Nothing’s more important in the backcountry than staying hydrated, but the
same water that quenches your thirst and keeps you alive can also sicken you
if you don’t take proper precautions. Out on a multiday backpacking or
paddling trek, you should play it safe and purify any water you’re using for
drinking or cooking. How? In this blog post, we’ll review the basic water
purification methods and when they should be employed.
But ... Do I Need to Purify Water in the Backcountry in
the First Place?
We already hear some of you questioning the whole premise. Can’t you drink
straight from that icefield trickle, that mossy seep, that babbling
high-country brook? What purer water could there be than that in the deep
wilderness? There are a lot of myths and misleading advice circulating
around wilderness water treatment. Some folks claim they’ve never purified
water in the backcountry, drinking freely from mountain streams and glacial
lakes without ever suffering negative consequences. It’s certainly true you
could go a lifetime of backpacking happily free of gastrointestinal
miseries, but you’re playing a game of chance. Those people who sup directly
from wilderness lakes and waterways and don’t contract waterborne
illnesses have had luck, an especially hardy immune system, or both on their
side. You’ll also hear it said that one used to be able to slurp
merrily from wilderness water sources, but that the pollutions and
contaminations of our modern world now preclude that option. Certainly we’ve
fouled watersheds all over with our activities, but many waterborne
pathogens exist naturally in even the most “pristine” basins. After all—and
not to get too graphic, but such is the nature of our subject—animals have
been answering Nature’s call, not to mention expiring, in lake shallows and
forest streams for eons. (They do call giardiasis “beaver fever,” after
all.) Water-related ailments have been a reality for humankind forever, and
countless ancestors of ours wandering much less trammeled and altered
landscapes died from waterborne germs. Now, it is true that some recent
research suggests wilderness water sources may be less biologically
contaminated than previously thought. But it’s impossible to judge by the
naked eye, so why tempt fate? It’s easy to be blasé about waterborne
illnesses until you’re hit with one. If it strikes when you’re back home in
civilization, it can be a miserable few days. If you’re still in the
backcountry when you fall ill, it’s that much more miserable—not to mention
more dangerous, because you’re less able to combat the dehydration that
arises from all that vomiting and diarrhea.
What is Purified Water?
For our purposes, purified water is that from which pathogens (“germs”) have
been removed or destroyed. And when we’re talking about pathogens a
backpacker or paddler is facing in the North American wilderness, we’re
talking about the following:
-
Bacteria:nasty
(to us, anyway) microbes such as Escherichia coli (“E. coli”)and Salmonella found
in many waterways.
-
Parasites:such
delightful critters as flatworms, tapeworms, and—most commonly
afflicting North American outdoorspeople—protozoa such as Cryptosporidium
parvum and Giardia lambia.
-
Viruses: generally
less of an issue in the U.S. and Canada, but Hepatitis A and others can
be a problem overseas.
The typical vehicle by which a stream, lake, snowfield, or other water
source becomes contaminated with such pathogens is animal waste (including
that of humans). As we alluded to above, carrion can also be the source. In
North America, backcountry pathogens are more likely to sicken you than kill
you (those with compromised immune systems are more at risk of serious
effects). The diseases they cause—giardiasis, for example, or
cryptosporidiosis—can certainly be highly debilitating, though, involving an
awful lot of stomach cramps, diarrhea, nausea, vomiting, fever, and other
torments.
How to Purify Water
There are three primary water purification methods: boiling, chemical
treatment, and filtration. Each has its benefits and drawbacks, and most
experienced backpackers don’t rely on any one alone; rather, they’ll use one
or another or a combination depending on the situation. Having backup
water-purification tools on hand is always a smart idea in case your primary
method fails or can’t be used.
Boiling Water for Drinking
Does boiling water purify it? Absolutely. In fact, boiling is the most
effective method of water purification: It kills all pathogens—viruses,
bacteria, and protozoa. The only drawback is the hassle, time, and fuel
required to bring water to a boil (and the time necessary for the boiled
water to cool to a safe drinking temperature).
How Long Do You Boil Water to Sterilize It?
Yes, there’s a time expense involved when getting water to boil and cooling
it down again, but the actual interval required to sterilize by this
surefire method is negligible. When you’re boiling water for drinking
purposes, heat to a rolling boil and keep it there for a full minute. As REI
notes, even the highly heat-resistant Hepatitis A perishes in 208°Fahrenheit
water in less than a minute. Now, what about the elevation factor? A bit of
a gray area. The Centers
for Disease Control and Prevention suggests you should extend the
rolling boil to three minutes at elevations above about 6,500 feet. Other
authorities claim that a minute’s sufficient regardless of elevation.
Chemical Treatment
Chemical treatment is used to kill or destroy waterborne pathogens. It’s a
straightforward process, if often a time-consuming one: You just plunk a
tablet, sprinkle powder, or squirt a droplet or two in the water you want to
treat and wait. Iodine is the best-known chemical
treatment: It’s effective in killing bacteria and viruses, less so protozoa.
Iodine can be used to treat for Giardia, but you typically have to
soak water for an hour to do so. Iodine doesn’t disinfect against Cryptosporidium. Chlorine is
an alternative chemical treatment with similar properties as iodine: good
against bacteria and viruses, so-so against protozoa. It may be somewhat
less effective than iodine in destroying the cysts of Giardia, and
like iodine doesn’t treat for Cryptosporidium. Chlorine
dioxide is a chemical that can, given enough time (up to four
hours), kill Cryptosporidium, though it’s not foolproof. Chemical
treatments such as iodine and chlorine tend to give treated water an
off-putting taste. Some tablets or powders come mixed with other agents to
counter that flavor, or you can add, say, Vitamin C before drinking.
Overall, chemical tablets or powder are lightweight and space-efficient; you
might as well have them handy as a backup means of water-treatment.
Survival Water Filtration
Unlike boiling or chemical treatments, water filtration doesn’t kill
pathogens but rather strains them out. As they’re typically 0.1 micron in
size or smaller, viruses are usually too miniscule to be filtered out. Some
filters include an iodine component to kill viruses (in which case they’re
more properly called water purifiers); otherwise, where viruses are
a concern you should disinfect the water with iodine before filtering or
else simply boil it. Pay attention to the pore measurement of a filter to
determine which kinds of pathogens it wards against. Choose filters with a
pore size of 0.4 microns or smaller. There’s quite the dizzying array of
water filters and purifiers on the market, from pump and gravity models to
squeeze-action ones. Again, pore size should be the deciding factor, but
personal preference and budget play a role, too. A benefit of the
squeeze-action water filters is they don’t have as many working parts to
break. Because sediment and other debris will gunk up a filter, they need to
be cleaned at varying intervals depending on design and degree of use. Many
come with a prefilter that strains out larger particulate matter before
water passes through the filter proper.
Where Should I Gather Water for Purification?
Where and how should you gather the water you’ll boil, treat, or
filter/purify for drinking and cooking purposes? Although, again, your naked
eye isn't an effective judge of the purity of water source, it’s certainly
better to avoid visually fouled ones: for example, those crossed by human or
animal trails, edged by heavy animal sign, or mucked over with algae, which
isn’t generally harmful in and of itself but which indicates biologically
fertile conditions that may breed pathogens. Flowing water is preferable to
stagnant water, clear water to murky water. If you can, fetch lakewater as
far offshore as you can. You can “prefilter” water of silt, plant bits, and
other debris using a bandanna spread over the mouth of your collecting
vessel. You can also cut down on the detritus in your water by facing your
vessel downstream.
Thanks to
Mountain
House Blogs for the above information.