Water

Purifying Water

Boiling, chemical disinfection, filtration and solar disinfection: what each method kills, what it misses, and how to do it right.

Field notes

Disinfecting Water with Household Bleach

8 drops of plain 5–9% bleach per gallon of clear water, stir, wait 30 minutes. Double it for cloudy or very cold water. The CDC table and the rules.

Critical
How to Boil Water to Make It Safe to Drink

Boiling is the most reliable way to kill germs in water. Bring clear water to a rolling boil for 1 minute, or 3 minutes above 6,500 feet.

Critical
Water Filters and Purification Tablets: What They Miss

Portable filters don't stop viruses, and iodine or chlorine tablets don't kill Cryptosporidium. How to combine methods so your water is actually safe.