AMERICAN RED CROSS STANDARD
1. Filter water using a piece of cloth or a coffee filter to remove solid particles.
2. Bring water to a rolling boil for about one full minute.
3. Let it cool at least 30 minutes. Water must be cool or the chlorine treatment described above will be useless.
4. Add the required amount of liquid chlorine bleach.
5. Let stand 30 minutes.
6. If it smells of chlorine, use it. If it does not have a chlorine scent, add 16 more drops of chlorine bleach per gallon of water (or 8 drops per 2-liter bottle of water), let stand 30 minutes, and smell it again. If it smells of chlorine, use it. If it does not, discard it and find another source of water.