Water Purification by Boiling

Use cloth, coffee filters, or sand if water looks dirty. Strain through multiple layers. This removes particles but does not kill pathogens—boiling is still required.

At sea level: boil for 1 minute. Above 6,500 feet: boil for 3 minutes. Above 10,000 feet: boil for 5 minutes. Higher altitude means lower boiling point, so longer time is needed to kill all pathogens.

Use a metal pot, kettle, or can placed directly on fire or coals. Ensure water reaches 212°F (100°C) at sea level. A vigorous rolling boil with large bubbles breaking the surface is what kills pathogens.

Remove pot from heat. Cover with a clean cloth or lid immediately. Do not leave open or exposed to air. Allow to cool on a clean surface. Avoid contact with contaminated hands or dirty surfaces.

Never put hot water on ground or unclean surfaces. Recontamination during cooling defeats all your work.

Use glass bottles, plastic bottles, or sealed metal containers. Keep containers covered to prevent airborne contamination and insects. Label with date boiled. Boiled water stays safe indefinitely if stored correctly and kept covered.

Boil large amounts at once, not small portions repeatedly. Cover pot with a lid to speed boiling. Let heat continue after fire is out by wrapping pot in cloth or blankets. Use every bit of fuel efficiency.