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How long to boil water to make it safe
Boiling is the surest way to kill bacteria, viruses and parasites. How long depends on how high up you are.
The rule
Bring clear water to a rolling boil for at least one minute. At altitudes above 1,000 metres (the EPA also gives 5,000 feet), boil it for three minutes, because water boils at a lower temperature higher up. Let it cool by itself and store it in clean, covered containers.
Tips
- If the water is cloudy, let it settle and filter it through a clean cloth or coffee filter first.
- Boiled water tastes flat; pouring it between two clean containers a few times puts air back in.
- Boiling does not remove chemicals, fuel or heavy metals. Water that may be polluted with chemicals needs a different source.
No way to boil? Use household bleach.
For planning and general information. In an emergency, follow the instructions of your local authorities and call your emergency number (911, 112, 999 or 000).