“Safe Water in Emergencies,” Ensign, Feb. 1986, 70–71
Safe Water in Emergencies
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:
1/4 tsp./gal. cloudy water
Let stand until clear
Approximately 3 Tbsp./gal.
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