Water should be filtered if it appears cloudy or if it has visible contaminates such as floating pieces of dirt or bark. To filter it, pour the water through a coffee filter, paper towel or cheese cloth. Throw away the visible contaminates. You may need to filter the water several times until it is clear or nearly clear. Filtering does not remove bacteria and should always be used concurrently with another purification technique.
Boiling is the most thorough water purification technique. Heating the water until it reaches a rolling boil will burn off contaminants such as bacteria and viruses. Hold the rolling boil for at least one minute. Let the water cool completely before drinking it. This will give the contaminants time to leave the water and will lower the temperature to a safe level.
If you don't have access to a heat source you can use bleach to remove bacteria and other contaminants from water. To use it, pour the proper amount of bleach into the water and let it sit for 30 minutes. Do not use bleach that contains fragrances or other additives. Use three drops of bleach per quart of water. The water might have a bleach taste or smell. This will not harm you, but you can remove it by pouring the water back and forth into two containers. This will cause the smell to dissipate.
If you cannot carry bleach with you or if you don't have access to a heat source, use iodine water purification tablets to remove contaminants and make water safe to drink. To use them, filter the water. Drop a tablet into the appropriate amount of water according to the size and type of tablet you are using. Mix the water until the tablet dissolves. Let the water sit according to the manufacturer's instructions.
