How Long to Boil Water For Drinking

How long to boil water for drinking. It’s good to know. And the time it takes is probably not as long as you may think…

90 percent of the world’s water is contaminated in some way according. That’s 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.

What about the following scenario… Dipping your head into a cold mountain stream and taking a long refreshing drink. Unfortunately that could lead to a bad experience… There are likely microscopic organisms in that water – those that could get you sick. Plus, you don’t know what’s upstream, possibly contributing to bad ‘stuff’ in the water.

With that said, in the wilderness, water coming from a natural spring is probably your best bet. However 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?

Biological contamination

– Water may contain microorganisms such as “Giardia” (common!) and if not killed, leads to intestinal disorders

– Water could also contain bacteria or viruses.

Traveler’s diarrhea
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 organic 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 (~160 F) 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 (about 90°C).

So you’re looking at “a few minutes” 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

[ Read: Water Filter – A Survival Prep ‘Must Have’ ]


  1. Boiling water takes a while over an open flame. Many times throughout my life, I’ve boiled the head/antlers of deer, European mount. It’s free and “what the heck.” I’ve done it over open fire, using drift wood or whatever I could find. It takes hours to do it, so a little liquid refreshment may be required.

    In shtf, a rocket stove would be well worth the effort to make. Fuel (wood) will become a valuable commodity. The concentrated high heat of a rocket stove works well. I’d never used one until I made my own. I was duly impressed.

    1. Yes indeed, my little rocket stove will get water to a boil right quick…!

  2. And don’t forget to boil your pet’s water. It needs to be safe to drink also.

  3. Thank you for the reminder, its important to know this stuff. When i was a kid i got a miserable intestinal bug from drinking bad water, will never forget it, couldnt eat solid food for 3 months or so. Not good

    1. People come up to go hiking and camping in the Appalachian mountains and enjoy the “crystal clear, clean” mountain streams and don’t filter or boil their water. Last week I found a dead fawn in one of my “crystal clear, clean” spring fed mountain streams and if you were 10 yards downstream you would have never known it.

  4. Almost 40 years ago, I bought and used the First Need water filter when traveling in the backcountry. It was much cheaper than the Katadyne filter and I was on GS-5 wages. I bought a new filter element every year and changed out the filter after it was frozen. (carbon composite filters do not tolerate being frozen…time to buy a new filter element). Depending upon where you live in the country, filtering your water may be a good idea even when living in a larger city. (City of Santa Barbara, CA had a water system over 100 years old and residents were drinking technically polluted water at certain times of the year).
    The default system to purify questionable water became boiling because a simple stove will always work and you can melt snow into water that can be run through a filter. (I carried coffee filters with me along with a funnel and my MSR stove). Melted snow and ice can still contain glacial silt, pine needles etc.
    After living off-grid for a number of years, I became very interested in household and municipal water treatment. Water quality and abundance is part of the reason I relocated to where I live now. There is no lack of fresh water falling from the sky in Western OR. The nearby city I work in had a do-not-drink notification for several months due to a toxin in the water from a type of blue-green algea. The water system was outdated and folks were obtaining water from wells that had no such toxins in it. The problem was not fixable by boiling the water either. The toxin was removed by adding and filtering out the toxin with activated carbon. The city made improvements to the water system and there has not been a repeat of this situation. I believe the Berkey filter-system has an activated carbon element integral to the system. (buy replacement filters made from activated charcoal for the Berkey or the First Need)

  5. in my youth my friends and i drank from so many springs and rivers in the Great Basin area and never got sick. we never thought about it in the 60’s and 70’s. i guess we got lucky. i wouldn’t take any chances now.

  6. you guys do know that getting contaminated water in your eyes or cuts is just as bad as drinking it. maybe worse, it goes straight into your bloodstream. and yes, your eye’s. watch what you wash with. i learned this from classes with the state health dept. working in hospitals. i took care of 5 of em, and many doctor and dentist offices in my before life. there is a reason that trauma doctors and surgeons wear eye shields.
    Cali can back me up on this one.

  7. Actuallly there is a very good reason to boil water for a longer time, and that is to evaporate other unwanted constituents – such as petroleum products, alcohols, medicines, plant fertilizers and supplements, etc. This process is technically called basic thermal cracking, and it is frequently used in manufacturing various chemicals.

    The vast majority of drinking water systems do nothing to get rid of these constituents. They just use the old “dilution is the solution to polllution” method.

    Many moons ago (60 years?) the Boy Scouts taught to boil water for 3 to 5 minutes in order to utilize this drinking water purification step. Of course the actual time needed for it to work depends on the substance involved and it’s vapor pressure, the temperature you use, and the atmospheric pressure. You can guess the time needed, but only a really good drinking water lab analysis will tell you what you really have to get rid of, and how to do it.

    By the way, this chemical procedure is used in many kinds of distillation, and is the reason for never saving the initial product from your moonshine, mercury, or herbal essence still. Only start saving your product AFTER you get rid of the nasties!

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