How long do i have to boil water for it to be safe to drink?

Just bring to boil: Just bring it to a boil then turn off the heat. (If high above sea level, e.g. in the mountains, it may be necessary to boil a few minutes.) There may be a few rare bacterial or parasites that require more prolonged boiling temperature before being killed, but too rare to worry about. If in doubt, check with the public health department in your area.

Reaches a boil: Once it reaches a rolling boil then give it 1 minute. That is the recommendation to kill any pathogens that would cause you harm.

Sterilize water: after boiling water for a few minutes, that will sterilize it and be able to drink ad lib.

1-3 minutes: According to the Washington State Department of Health and the United States Environmental Protection Agency, you should bring the water to boil and keep it rolling for one minute to purify it. At altitudes above one mile, 2,000 meters, you should increase the rolling time to three minutes.

Wait: Boiling water is never safe to drink. Attempting to do this can cause severe injury and death. Boil the water, filter it, and allow it to cool before using it for cooking or drinking. Always test the temperature before giving it to a child or an elderly person.