How Long to Boil Drinking Water until Safe or Disinfected?

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?

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 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

Related: Water Filter – A Survival Prep ‘Must Have’

Katadyn Pocket Filter 0.2 microns

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

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  1. Ok, I’m going to add a couple of Common Sense items here just cause.

    1. Do not take a drinking cup/storage container, dip the ‘contaminated water than pour it into the boiling pot, boil, it than return it to the Drinking Cup

    2. And I have seen this done, make sure the water is cooled BEFORE drinking it

    3. Make sure you have a “CLEAN” vessel to store extra water in

    4. Put a lid on the Boiling Container to conserve fuel

    5. If you plan on only heating water to 160 deg. how do you know it’s 160 and not 140 without a Thermometer? Boil it.

    6. Got a hot-pad or gloves for the 212 deg. boiling pot of water you’re reaching for?

    I will admit that sta. of 90% of water is contaminated is quite shocking, makes ya wonder how “clean” that Tap-Water really is don’t it?

    Here is a little fact I dug up, again Just Cause; As per the “WHO/UNICEF Joint Monitoring Program 2017 report on the progress of drinking water recently published its 2017 update”….
    “Every year there are more than 3.4 million deaths from waterborne diseases, making it the leading cause of disease and death around the world.”

    What’s in your water????

  2. If you want to store Berkey filters activate them 1st in clean water and let dry for about 2 weeks turning every 3 days or so. This will prevent having to deal with finding clean water to activate.

    Not to hijack the thread, but I just set up a new Berkey with the two black filters down in coastal FL. The filter was unable to strain slightly sulphuric/swampy taste and smell out of the water. I thought the Berkey was supposed to convert pretty much any variant of H2O to clear pure water. Could they have sold me a “Chinese” filter? Any thoughts appreciated.

    1. That “gassy” swampy smell will only dissipate on aeration of the water. Multiple filtrations will be needed.

    2. Bogan,

      1 Did you flush the filters prior to use as stated in the manual ?

      2 use red food coloring to check the filtration it should come out clean.

      3 I’ve heard some water in Florida are really high in sulfur content.

      1. By the way, the ‘food coloring’ test is not definitive. It’s water soluble so it may get through the filter pores anyway indicating a false-positive. “Most dyes go into solution (molecular), not suspension (particle) form”. Note that a charcoal filter stage may absorb food coloring, but charcoal is for neutralization of odor and flavor.

  4. I just boil it. Still taste terrible but it is what it is.
    As NRP states be very careful of cross contamination during filtering or boiling. I’ve made mistakes and paid for them.

    1. Or make beer. There’s a reason why our ancestors brewed beer. It was safer than drinking water.

  5. Boiling town tap water also rids the mandated Chlorine and Fluoride.

    Less chemicals inside you = good.

    Those ice machines in restaurants rarely are cleaned – be wary of icy sodas.

    Do not consume drinks with ice in third world countries. The drink itself may have been sterilised but the ice may have been made from unfiltered tap water. The drinking container may also not have been washed in unfiltered or unsterilised hot water.

    Never drink the water in hotel rooms in third world countries. The maid may have filled up the water jug with tap water. Check any mineral water bottle carefully and make sure it’s not been tampered with. Maids often open the bottled water, drink the contents and fill them up again with tap water.

    1. Les Francis,

      Just to be clear, boiling does NOT remove Fluoride from water. In fact it will concentrate it as the water boils down.

      For ‘in-the-home’ ordinary use for filtering tap water (fluoride concerns), one filter that has good specs is this one, which also filters out fluoride and puts the Brita to shame:

      “Aquagear Water Filter Pitcher”

      Boiling will indeed speed up the evaporation process to rid chlorine. Charcoal filter will also bind the chlorine ions to the surface of the charcoal.

      Also, thanks for bringing up the good advice regarding ice! Some people may not think of that…

  6. We had a real crappy situation in Cozumel Mexico a few years ago . The hotel manager said only drink the bottled water in your room , no tap water .We did, but 1 morning we noticed the gardener filling the water bottles with a garden hose out in the patio. Too late , most of our group had been staying hydrated with the room water bottles . Montezuma got his revenge !

    1. Kevin, I remember watching the guy on doomsday preppers drink out of a toilet. I almost puked….

  7. I’m one of those people who over boils. I’m aware that statistically I don’t need to, and I think it’s important that if you do over boil, you do so of choice, not because you’re uneducated on the recommended times. I prefer to over boil to protect against the unknown. The new yet to be discovered stronger virus or bacteria that being at the wrong place and time puts in my cup. I’m not interested in being a patient zero. However, sometimes you can’t spare the fuel/power to over boil, and that’s where knowing your recommended times is important.

  8. I’m with Yolo. Overdo it. I just got done with a 2 week stint in Ecuador, with Quito being our base at 9,000 feet altitude – and we went up in altitude from there.

    I was the oldtimer in the group. At my insistence every evening we brought a large pot of tap water to a rolling boil and let it run for 20 minutes before allowing to cool down. We set a timer, to be sure.

    Still there was a thin film on top – whatever that was.

    In the morning we filtered it through three coffee filters (one over the top of the next), and distributed it to our water bottles , and into jugs for cooking, etc. I got the rolling eyeballs at first, but that settled down as time…and results …. took hold.

    Bottom line: no Montezuma’s revenge for anyone in my little group. Take that Giardia!!!!!!!

    At my age “good enough” seems like cutting corners. This is something you have control over, so IMO do it right!!!!!!!

    1. If you’ve got the time and fuel, better safe than sorry, right? Though ‘technically’ you would have been good-to-go at the initial rolling boil ;) A good margin though ensures a better feeling of confidence!

  9. Is giardia a concern for water used for basic sanitation such as washing hands? Or does that water need to be boiled too.

  10. I live in a trailer park that has well water, it has no bad smell, taste or color, am i being to cautious to boil it for drinking? Would a Brita or another filter work as well. I dont trust the water

  11. I live in a trailer park that has well water, it has no bad smell, taste or color, am i being to cautious to boil it for drinking? Would a Brita or another filter work as well. I dont trust the water

    1. DP
      I would get a Berkey water purifier, it will provide potable water from any source

    2. I would ask to see the water report. Our well water (same as city water) is tested by state regulation. Still wouldn’t hurt anything to run your drinking water through a Berkey.

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