Ways to Treat Water

In addition to having a bad odor and taste, contaminated water can contain microorganisms that cause diseases such as dysentery, typhoid and hepatitis. You should treat all water of uncertain purity before using it for drinking, food preparation or hygiene.

There are many ways to treat water for human consumption. None is perfect. Often the best solution is a combination of methods.

The following measures will kill most microbes but will not remove other contaminants such as heavy metals, salts and most other chemicals. Before treating, let any suspended particles settle to the bottom, or strain them through layers of paper towel or clean cloth.


Boiling is the safest method of treating water. Bring water to a rolling boil for 3 to 5 minutes, keeping in mind that some water will evaporate. Of course, let the water cool before drinking.

Boiled water will taste better if you put oxygen back into it by pouring the water back and forth between two clean containers. This will also improve the taste of stored water.

You can use household liquid bleach to kill microorganisms. Use only regular household liquid bleach that contains 5.25% sodium hypochlorite. Do not use scented bleaches, color safe bleaches or bleaches with added cleaners.

The American Red Cross recommends that you add 16 drops of bleach (a quarter teaspoon) per gallon of water, stir and let stand for 30 minutes. If the water does not have a slight bleach odor, repeat the dosage and let stand another 15 minutes.

The only agent used to treat water should be household liquid bleach. Other chemicals, such as iodine or water treatment products sold in camping or surplus stores that do not contain 5.25% sodium hypochlorite as the only active ingredient, are not recommended for use by the American Red Cross.

While the 2 methods described above will kill most microbes in water, distillation will remove microbes that resist these methods, and heavy metals, salts and most other chemicals.

Distillation involves boiling water and then collecting the vapor that condenses back to water. The condensed vapor will not include salt and other impurities. To distill, fill a pot halfway with water. Tie a cup to the handle on the pot's lid so that the cup will hang right-side-up when the lid is upside-down (make sure the cup is not dangling into the water) and boil the water for 20 minutes. The water that drips from the lid into the cup is distilled.