Last updated on January 31st, 2019
90 percent of the world’s water is contaminated in some way according to the U.S. Environmental Protection Agency. There are a variety of microscopic organisms that can contaminate water supplies. They can cause potentially serious, even fatal, illnesses among wilderness travelers.
Dipping your head into a cold mountain stream and taking a long refreshing drink. It’s an experience that has basically vanished from the wilderness and other areas.
In the wilderness, water coming from a natural spring is probably your best bet. Most issues are not knowing the source or what’s in between. There are very few places where you might be certain that the water is safe to drink.
How Long To Boil Drinking Water – How Many Minutes
How many minutes does it take to boil water until it’s safe to drink?
The quick answer (read on for more detail and caveats)
By the time water reaches a rolling boil, it will be safe to drink.
(altitude explanation below).
– Rolling Boil: Instant Safe. The CDC suggests adding 1 minute for safety margin
Why Boil Water?
– Water may contain microorganisms such as “Giardia” (common!) and if not killed, leads to intestinal disorders
– Water could also contain bacteria or viruses.
Ever been afflicted while on a vacation or hiking or camping? It most likely was caused by contaminated drinking water that you thought was perfectly safe… “Giardia”.
Time To Boil Drinking Water
Boiling is the most certain way of killing all microorganisms.
According to the Wilderness Medical Society:
Water temperatures at 160°F (70°C) kill all pathogens within 30 minutes.
185°F (85°C) will kill all pathogens within a few minutes.
Water that has reached a rolling boil will have killed all pathogens.
So in the time it takes for water to reach the boiling point all pathogens will be killed. The moment your drinking water reaches a rolling boil, the water has already become safe to drink.
According to the World Health Organization:
Looking at their collection of testing records & data for bacteria, virus, and protozoa (source below), the worst common denominator is for Giardia (protozoa).
They note 10 minutes at 70°C will provide ‘2 log’ thermal inactivation of Giardia. The problem is (at that temperature) we’re only looking at 99% reduction. We would like to see 4 or even 5 log (99.99% to 99.999%).
According to the Centers for Disease Control (CDC):
“Water should be brought to a boil for 1 minute”
(altitude caveat below)
Caveats: Boiling Drinking Water & Safety
1. Boiling water will NOT remove chemical toxins that may be present. Water may be toxic from sources like pesticide runoffs, direct dumping or indirect leaching, mine tailings, and so on.
Boiling, filtering, or chemically treating water can remove or kill microorganisms, but it will not remove chemical toxins.
2. Filter dirty water with a cloth or other material to remove sediments. You might let it stand for awhile to allow sediments to settle – then pour off clearer water on top. A coffee filter makes for a good sediment trap.
Altitude Affects on Boiling Water
Boiling temperature changes with altitude.
The higher you are, the lower the boiling temperature of water.
At 10,000 feet, water boils at 193°F (just about 90°C).
So you’re looking at “a few minutes” tops, to sterilize water.
The CDC recommends boiling water for 3 minutes at altitudes above ~6,500 feet (2000 meters).
Stop wasting fuel! You do not need to boil water for 5 minutes, 10 minutes, 20 minutes. Or “double for high altitude”, or whatever else you’ve heard.
How Many Minutes To Boil Water Until Safe To Drink
30 minutes at 160°F
3 minutes at 185°F
Instant at boiling
CDC: Drinking Water Treatment Methods for Backcountry and Travel Use
World Health Organization – Technical Brief “Boil Water”
Wilderness Medical Society
Engineering Toolbox: Boiling Point of Water and Altitude