The Food and Drug Administration, in cooperation with the United States Department of Agriculture Extension Service and the Environmental Protection Agency Safe Water Hotline, have determined that the following information about water storage and purification is the latest and most accurate information available.

If you give out information about water storage or purification, please ensure that these guidelines are provided:

Storage of Water

If using tap water that is chemically treated (such as provided from a commercial water utility company), note the following:

Store water in clear plastic containers, such as 2-liter soda bottles, with tight-fitting screw-cap lids. Milk containers are not recommended because they do not seal well. Do not add bleach or any other agent to the water. It is already chemically treated, so it does not need to be treated further. Rotate the water at least every four months.

If using water from a well or spring that is not chemically treated, the following applies:

• Store water in clear plastic containers, such as 2-liter soda bottles, with tight-fitting screw-cap lids. Milk containers are not recommended because they do not seal well.
• Add two drops of liquid household bleach per gallon of water. Make sure that 5.25% sodium hypochlorite is the only active ingredient. There should not be any added soap or fragrances.
• Rotate the water at least every four months.

If using commercially prepared "spring" or "drinking" water:

• Keep the water in its original sealed container.
• Once opened, use it and do not store it further.
• Rotate the water at least every six months.

Treatment of-Water of Questionable Purity

In addition to having a bad odor and taste, water from questionable sources may be contaminated by a variety of microorganisms, including single-cellular parasites such as Giardia, that cause diseases such as dysentery, cholera, typhoid, and hepatitis. All water of uncertain purity should be purified before use. To purify water, follow these steps:

• Filter the water to remove as many solids as possible.
• Bring it to a rumbling boil for a full 10 minutes.
• Let it cool at least 30 minutes.
• Add 8 drops of liquid chlorine bleach per gallon of cool water. Water must be cool or the chlorine will dissipate and be rendered useless. 5.25% sodium hypochlorite should be the only active ingredient. There should not be any added soap or fragrances.
• Let stand 30 minutes.
• If it smells of chlorine, you can use it. If it does not smell of chlorine, add 8 more drops of chlorine bleach, let stand 30 minutes, and smell it again. If it smells of chlorine, you can use it. If it does not smell of chlorine, discard it and find another source of water.

Past Information "out there" that has changed

The only agent to use to purify water should be liquid household bleach. Other chemicals, such as iodine or products sold in camping or surplus stores for water treatment that do not contain 5.25% sodium hypochlorite as the only active ingredient, ARE NOT RECOMMENDED AND SHOULD NOT BE USED.

The only accepted measurement of chlorine (or water treatment agents) is the drop. A drop is specifically measurable. Other measures such as "capful" or "scant teaspoon" are not uniformly measurable, and are not to be used. There is no difference between treatment of potentially contaminated water that is cloudy or clear.