Boil all water from the wild before drinking; a rolling boil for one minute is enough, and you don't need to boil longer at high altitude

In a real emergency, call 911 first, then read this.

Cost

The extra weight of a stove and fuel.

What you get

Every microbe that can make you sick through drinking water is killed (inactivated) within seconds at the temperature of boiling water. "Water at high altitude doesn't get hot enough" is a common misunderstanding

Notes

The same page also says you don't actually have to boil it: 60 ℃ held for 30 minutes works equally well, and boiling is only an endpoint you can see without a thermometer. If you can't boil, use a filter or chemical disinfecting tablets, but each has germs it doesn't cover, so boil if you can. A clear-looking stream or snowmelt can carry parasites just the same, so don't judge by appearance.

Evidence grade

B : Supported by research but without a precise number, or based on small or single studies.

Sources

1. 美国疾病控制与预防中心. 黄皮书·旅行者的水消毒：「All organisms that may cause illness from drinking water are killed within seconds at boiling temperature」「CDC recommends that travelers boil water for a full minute to account for user variability in identifying boiling points and to add a margin of safety」「Although the boiling point for water decreases with increasing elevation, at common travel elevations the temperature needed to achieve boiling is still well above the temperature required to inactivate enteric pathogens」. https://www.cdc.gov/yellow-book/hcp/preparing-international-travelers/water-disinfection-for-travelers.html

Translated from the Chinese original. Original book, section 13, tip 35. Content may be out of date and rules differ by place. When you actually deal with an agency, a doctor or a court, follow what local officials, doctors and lawyers tell you. Disclaimer