WARNING: We provide the following emergency water purification method for use strictly as a general guide and not as a guaranteed method for manufacturing safe, clean drinking water. Every emergency situation has different factors these instructions do not take into account. We make no guarantee that these instructions will work in all situations.
With that out of the way, please remember that the best preparation for an emergency begins long before the event takes or looms on the immediate horizon. Properly planning and preparing by stockpiling clean drinking water, emergency rations, candles, a radio that receives NOAA broadcasts, weather resistant gear, waterproof matches, a tarp, blankets, medical supplies, a supply unscented chlorine bleach, etc. can lessen the immediate sting of a short-term emergency and make surviving longer emergencies more likely.
1. After collecting the water in a container, let any suspended particles settle to the bottom and gently pour the clear water off the top into a second container. Filter this water using a clean piece of cloth or coffee filter to remove any remaining particles.
2. To disinfect by boiling, bring the water to a rolling boil and boil for a least 1 minute. Boil longer at high attitudes or if the water is from a source suspected to have Giardia or other protozoa (5 minutes boiling time is recommended at 10,000 feet above sea level). Boiling will kill disease-causing microorganisms present in water, but will concentrate non-volatile chemical contaminates, so it is unwise to boil for longer than necessary.
3. Let the water cool at least 30 minutes. You can re-oxygenate the water by pouring the water back and forth between two clean containers. This will improve the taste.
4. To disinfect by chlorination, use ordinary household chlorine bleach. Sodium hypochlorite with a concentration of 5.25% to 6% should be the only active ingredient in the bleach. There should not be any added soap or fragrances. One major bleach manufacturer has also added sodium hydroxide as an active ingredient, which will not pose a health risk for water treatment. Add 16 drops (¼ teaspoon) of liquid chlorine bleach per gallon of water, or 8 drops per 2-liter bottle of water. Stir to mix. If you do not have a dropper, use the following (instructions) to measure the correct amount of bleach.
8 drops = 1/8 teaspoon, 16 drops = 1/4 teaspoon and 32 drops = 1/2 teaspoon.
5. Let the water stand 30 minutes to give the chlorine time to kill the microorganisms present. This method is not guaranteed to be effective against certain encysted protozoa.
6. If it smells of chlorine, you can use it. If it does not smell of chlorine, add 16 more drops of chlorine bleach per gallon of water (or 8 drops per 2-liter bottle of water), stir, let it 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. The only agent used to purify 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 percent sodium hypochlorite are not recommended.
7. If the chlorine taste in the water is too strong after disinfection, pour it from one clean container to another several times. This will drive some of the chlorine off as a gas, lowering the level of chlorine in the water and improving the taste.
Not to sound like a broken record, but the creators of the instructions above (and ANY instructions you read on the internet or in books/magazines) could not possibly know the exact specifics of every situation where a person or group needs to create safe drinking water. Nor could they know the full list of contaminants one might find in their source water. Use the above instructions as a general guide only.