Boiling water. If commercially bottled water is not available, boil your tap water. To kill germs, bring water to a full rolling boil for 1 minute. At elevations above 6,500 feet, boil for 3 minutes. To avoid burns, allow boiled water to cool before you use it. Boil your tap water even if you filter it. For example, still boil tap water if it ... More @Wikipedia
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