Water
Adjust water boil time for altitude
Water boils at lower temperatures at high altitude, so you need longer boil times to reliably kill pathogens.
Topic summary
Water boils at lower temperatures at high altitude, so you need longer boil times to reliably kill pathogens.
Intended uses
Water skill (all levels, ~5 min practice)
Step-by-step
Below 6,500 feet (2,000 m): a rolling boil for 1 minute kills all common waterborne pathogens.
Above 6,500 feet: extend to a full 3 minutes at a rolling boil.
Do not rely on 'just to a boil' at any elevation — the water must maintain a full rolling boil for the timed interval.
For extra confidence in remote alpine environments, use both a filter and a boil.
Filter cloudy water through cloth before boiling so heat doesn't waste on sediment.
Warning: Boiling does not remove chemical contamination — heavy metals, salts, and industrial pollutants stay in the water. Only pathogens die.
Related outdoor skills
Educational reference only. Wilderness conditions change fast — practice in low-stakes settings, take a certified wilderness first-aid course, and confirm regional regulations before you rely on any of these skills in the field.