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Obtaining good-tasting, contamination-free water is ordinarily not
a problem. But in times of emergency, on outdoor trips, or when traveling
in under-developed areas, having access to a source of drinkable
water is a matter of first priority. The bacteria, viruses, and parasites
in contaminated water can create many kinds of health problems. When
the purity of water is questionable, use the following steps to make
it safe to drink:
1. Clarify cloudy water by adding a small amount of powdered kitchen
alum—about 1/4 level teaspoon per gallon. Larger amounts are
not more effective! Crystals take much longer to dissolve than does
powder. The alum reacts with the water, producing a precipitate which
slowly settles and absorbs impurities. After settling is complete
(fifteen minutes to an hour or two, depending on the water) pour
the water into another container, being careful not to stir up the
sludge at the bottom. Discard the sludge, and the water is ready
to be disinfected. If you don’t have any alum, filter the water
through a tightly woven cloth. Clarification is important; clear
water can be purified using less chlorine or iodine than you need
for cloudy water. When the water is clear, you are ready to disinfect
it.
2. Disinfect the water by one of the following methods:
Boiling. Boil the water at least three minutes after it has come
to a rolling boil. This is the best method if fuel is available.
(At elevations of ten thousand feet or more, water should be boiled
for fifteen minutes because it boils at a lower temperature at higher
elevations.)
Chlorine. Add five drops of chlorine bleach solution (4 to 6 percent
hypochlorite solutions such as Clorox or Purex work well) per quart
of water. Let the water stand thirty minutes. If there is no residual
odor of chlorine, repeat the treatment until a definite chlorine
odor remains. A small plastic bottle of bleach solution will purify
a lot of water, but the chlorine solution deteriorates with time,
so replace your bottle on a yearly basis. Halazone tablets release
chlorine slowly, but they are expensive, have a relatively short
shelf life, and are less effective.
Iodine. Add eight drops of a 2 percent tincture of iodine solution
(obtainable at most pharmacies) to a quart of water, and let stand
about thirty minutes.
Best of all, you can make your own iodine solution with about five
grams of iodine crystals (also obtainable at most pharmacies) in
a two-ounce glass prescription bottle. (Plastic bottles darken after
a while.) Cover the crystals with a small amount of water to retard
sublimation. Freezing this mixture should not crack the container.
When you are ready to use the iodine solution, fill the two-ounce
prescription bottle with water, put the cap on, and shake the bottle
for several minutes. Let the heavy crystals settle, then carefully
pour out approximately three tablespoons (almost all the solution)
into a gallon of clear water. Stir, and let the water stand for approximately
thirty minutes. If the water is ice cold, let it stand for an hour.
If you find the taste of iodine objectionable, use half the amount
of iodine solution, and let the treated water stand twice as long.
(Most people find the iodine taste less objectionable than that of
chlorine in chlorinated water.) Use only the iodine solution; leave
the crystals in the bottle. You can use the crystals up to about
three hundred times before they completely dissolve.
Keep the solid iodine away from children. Do not touch the crystals!
Solid iodine is very irritating to the skin and will stain most things
it touches, although alcohol will dissolve it readily. The violet
vapors are very corrosive!
The iodine crystal method of water purification is inexpensive,
and actually more effective than chlorination. As solid iodine has
an indefinite shelf life, one bottle should last a lifetime for emergency
use.
As a reminder, put labels on the alum and iodine containers:
Kitchen Alum
1/4 tsp./gal. cloudy water
Let stand until clear
Iodine Solution
Approximately 3 Tbsp./gal.
clear water
Let stand approximately thirty minutes.
We have used the alum clarification and iodine disinfection methods
successfully on many backpacking and canoeing trips. Only persons
who are sensitive to iodine or who are being treated for hyperthyroidism
might suffer any ill effects from this method; no other adverse physiological
symptoms have been noted in tests using sample groups.
Byron J. Wilson and H. Smith Broadbent, Provo, Utah
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