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How Long Should You Boil Water?

In this guide we show you how long to boil water before using it. Learn how to make your water safe to use without wasting fuel.

Today a friend asked me, “How long should I boil my water?”.

He’s a prepper and a smart guy, but it’s no surprise to me that he’s confused on such a seemingly simple topic.

I frequently come upon bad advice on blogs, books and forums about boiling water for purification.

It’s something we all need to learn too.

Unless you have a tree limb stuck through your leg or a bear staring you down, having enough safe drinking water should be your number one concern.

Unless Your Water Is Toxic, Boiling Water is the Best Method

Boiling kills bacteria, viruses, protozoan’s, and parasites. It does NOT remove chemicals and toxins from the water. Surprisingly not many survival article cover this side of the conversation.

If you’re getting your water out of a perfect mountain stream, then boiling it is probably all you need to do. But if your water source is a lake or river that collects runoff from cities, then you need a chemical water filter.

You’ve got to take the chemicals out of your water before you boil or you will just concentrate them.

Even rain harvested from roofs or plastic lined depressions in the ground may contain some nasty chemicals. Rain can contain a multitude of dangerous chemicals, especially if you live in or near an urban environment.

Assuming your water is chemical free, modern filtering devices and the chemical treatment of water are only faster substitutes for actually boiling the water.

Boiling water is sustainable, unlike filters and chemical treatment. As long as you have a source of heat and a fireproof vessel of some sort you can boil water.

The Case For A Lid

Whatever pot you use to boil your water in, make sure it has a lid. Boiling water without a lid is a huge waste of resources.

Not only is your water evaporating right before your eyes but you are wasting heat as well. Doing something as simple as placing a good fitting lid on your pot can cut the time it takes for your water to boil significantly.

Pasteurizing water also works much better with a lid as it traps the heat inside the container for a much longer time.

Commonly Stated Water Boiling Times

There are so many varying boiling times out there that it will make your head spin. It seems like most people spout facts based on personal choice with no scientific proof to back it up.

Even different government and health organizations cannot agree on a correct time (what a surprise).

The most common stated water boiling times:

  • “Boil water for 10 minutes”
  • “5-minutes of boiling”
  • “Boil the water for 20 minutes”
  • “A rolling boil for 1 minute”
  • “When at high altitudes you need to boil water for twice as long”

So which of the above statements are actually true? None!

That’s right. Follow any of the above times and you will waste two of your biggest resources, water and fuel.

Wasting water to evaporation when you’re short on water to begin with is foolish. Whole forests have been cut down for firewood in order to boil drinking water.

Weekend hikers and tough mountain men alike have used up the last of their precious fuel to boil water for crazy amounts of time. In a survival situation you cannot afford to waste valuable resources and energy like this…

The Correct Water Boiling Time

The correct amount of time to boil water is a whopping 0 minutes. Thats right, zero minutes. None. Nada. Zip. Zero. Read below…

According to the Wilderness Medical Society, water temperatures above 160° F (70° C) kill all pathogens within 30 minutes and above 185° F (85° C) within a few minutes. So in the time it takes for the water to reach the boiling point (212° F or 100° C) from 160° F (70° C), all pathogens will be killed, even at high altitude.

What is not well known is that contaminated water can be pasteurized at temperatures well below boiling, just like milk, which is commonly pasteurized at  160°F (71°C)….

The truth is, with a water temperature of 160 to 165 degrees F (74 C) it takes just half an hour to pasteurize. At 185 degrees this is cut to just a few minutes and by the time water begins to boil at 212 F (100 C) the water is completely safe unless it has large particles floating of gunk around in it.

I still like to let my water sit in the pot for a minute and cool a bit. This extra time gives the water a little bit longer to pasteurize.

Dirty water

If your water is muddy, cloudy, or has organic particles such as wood or grass floating around in it then you have to boil it longer, upwards of 10 minutes at a steady boil. This is because you have to heat the internal temps of all that residue to at least 160 degrees F (74 C) too. Otherwise they could be harboring some nasty bacteria and other stuff.

If your water is this dirty you should filter it using some sort of filter system, whether a commercial system or something built on the fly or just an old t-shirt. This will save time and fuel in the long run and ensure that your water is as safe as possible.

High Altitudes

So what about high altitudes? At high altitudes the time it takes for the water to reach a rolling boil and then cool means you can safely drink it. If you live above 2,000- 3,000 ft altitude make sure you let your water sit in the pot (with a lid on it) until it cools before drinking.

If you’re making a tea or coffee make sure you let it sit and then reheat it to the desired temperature.

You don’t need a thermometer to measure water temperature either, just take your water to a full boil and then immediately take it off the heat. Leave the lid on (you do have a lid don’t you?).

By the time it comes to a rolling boil you’ve wasted time, fuel, and water.

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Meet The Author

Sergeant Survival

Sergeant Survival

I spread the news of disaster preparedness and homesteading skills to the masses. My mission is to teach the keyboard commandos out there some real life skills.


Add a Comment
  1. Wow. I had totally forgot about the chemicals in the water. All the medications that people use and stuff like that. A lot of people forget about how important water is.

    1. Yep, those nasty chemicals can be a real problem. Living near a farm or runoff can make your ground water non-potable, and drinking downstream of a large city can be just as dangerous.

  2. Thank you! I took a food and safety course and they too said 160+, what I never put together was that water works the same way as food (kind of obvious after the fact:)

    I always boiled my water for about 10 minutes and always wondered if it was overkill, thanks again!

  3. finally true information. I know about clean water and refute many peoples advice, but yours is correct. thanks

  4. I’ve been trying to tell people for YEARS that the ‘survival’ information about boiling times have been exaggerated. But, as tends to be typical, they quote ‘this guy’ or ‘that course’ or ‘this organization’ without actually LOOKING at the scientific FACTS!!

    We drink milk that’s been pasteurized BELOW 80C (and canned foods) but boil the living CRAP out of our ‘camp’ water for NO GOOD reason.

    Several years ago, after MUCH research and many sources, I put together a little Power Point presentation including some of the information you stated above; including ‘what kills the bad things’ and ‘effects of altitude on boiling times’. Such as, time from 80C to boiling (100C) and the time it takes to cool before you can actually touch the water, as well as boiling times relative to altitude (higher you go, lower the temp. it boils, longer you need to boil it).

    My conclusion (relative to North America) was that for most locations, unless you’re on top of some really tall mountains (mountains over 5,000m), a rolling boil is all you need. If you happen to be mountain topping, then let it boil a couple minutes, but don’t waste your fuel boiling it for any longer. IF you’re above 6100m, you can’t boil water hot enough to pasteurize it in mere minutes (it boils 80C which is any where below 5000m/16400ft) is all you need unless you’re at altitudes FAR ABOVE the treeline (treelines are around 3000m/10,000ft). And if you’re above the treeline (or somewhere without trees), you NEED to conserve fuel because you HAD to haul fuel with you…there’s NO TREES for fuel!! For those above 5000m, for added assurance, boil for 3 minutes but NO LONGER. But not many people ‘bushcraft’ above 5000m, its not exactly ‘bush’ anymore.

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How Long Should You Boil Water?

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