How Long Do You Need To Boil Water?

According to the Centers for Disease Control and the Environmental Protection Agency, you are supposed to boil water vigorously for 1 minute and allowed to cool to room temperature and at altitudes greater than 6,562 feet, water should be boiled for 3 minutes.

http://www.cdc.gov/travel/water_treatment.htm

http://www.epa.gov/safewater/faq/emerg.html

I did a search of some .edu sites, and they recommend boiling in ranges of between 3-10 minutes. In a survival situation, where water and fuel are scarce, boiling water for 1 to 3 minutes is probably prudent. Otherwise, 3-10 would probably be advisable.

- SurvivalTopics Admin - This is precisely what we wrote about in the article: the times for boiling water given by these sources are all over the place. Fuel is being wasted boiling water for too long, and in developing countries or survival situations fuel conservation is critical.

The main thing is that the water has become hot enough (which visibly boiling water insures). It will take quite some time for the water to reach the boiling point and additional time for it to cool to drinking temperature.

See the Survival Topic "How Long Must Water Be Boiled Revisited" for further discussion. 

I've always thought that just getting water to boil would be enough.

Wow. This is News. I've been boiling like a madman. I bet the concerned people planting trees in developing countries are boiling like a madman as well. This needs to be told to everyone. And I've nothing against planting trees. It's a good too.

If you use cold water, before you boil it, there will be less dissolved solids suspended in the water, making it slightly safer

I think the "boil for 10 minutes" crowd are worried about bacterial spores; however, these pathogens rarely cause waterborne illness.

Most organisms will die at the boiling point, but MOST IMPORTANTLY giardia cysts do not. After five minutes of boiling, giardia should be neutralized. In situations where giardia (or other cysts) are a risk, I would not be confident with 0 minutes.

- Survival Topics Admin -  Giardia cysts are inactivated after 5 minutes in water at 55 degrees C (131 F) or immediately in boiling water. source: http://campushealth.unc.edu/content/view/599/51/

For some issues I believe it is the boiling, not the temperature that makes the water safe. The boiling shakes the water-borne particles 'to death'.

Not to be irritating, but couldn't there be other things in the water that could be dangerous for you, that will not die from boiling? Stuff like chemicals for instance. I assume that boiling and then running it through some filter would help you double up. Especially if that water you started out with came from a tap for instance. Chlorinated water does taste pretty awful at least:)

- Survival Topics Admin - Thank you for mentioning this, John.  Yes, heating water will only destroy pathogens but chemical pollution will not be eliminated in this manner. 

I'll generally agree with your argument right up to the point where you talk about high altitudes, where you went astray.

SO... if you're up at a high altitude like climbing Everest, it is NOT sufficient merely to boil the water. The boiling point may be too low to kill all microorganisms.

- Survival Topics Admin - Even at high altitudes, the temperature of the water when it reaches a boil is enough to eliminate pathogens.

At 10,000 feet above sea level the typical boiling point of water is 193 degrees F, well above the temperature required to destroy disease causing organisms.

source: http://www.hi-tm.com/Documents/Calib-boil.html#tables 

Terrific article. The other time suggestions were obviously made with no research, and with no consideration to a scarce fuel supply.

hehehe that was my 1st answer, water boils @ 212, no need to "boil" for "x" minutes.

I notice no comments on this ...lesson complete 8-).

allfury

What's the correct boiling time at an altitude of 10000 ft?

finally i have proof! no one believes me when i tell them to just bring it to a rolling boil!

You are wrong about the high altitude point. Boiling points of liquids depend on the altitude so at high altitudes it will boil at a temperature less than 100 C. So depending on the altitude you will need to let the water boil for a few minutes before its safe to drink.

Great info, I will keep this nugget of info will me and share it with others. Thanks.

0 minutes? I remember a pathology course some years back where we learned of certain organisms that go into a spore-state that can survive boiling, but are forced out of the spore state once they've been through a heated phase. A second boiling would then kill the "hatched" bug. Wish I could remember the parasite, but it escapes me.

- Survival Topics Admin - Indeed, such spores exist. Even boiling the water for 10-minutes or more would probably not destroy them.  There is only so much one can do to purify water or food - these spores are generally harmless.

Great article. It's good to know. Once, ten years ago, I was in a situation when I was wanderin' about time necesary to boil water to make it drinkable. Wish I read this at the time...

I heard you can just take an eyedropper and squirt a few drops of bleach in your water and it'll be safe.

- Survival Topics Admin - Chemicals and filtering are not reliable ways of making water safe to drink. Better than nothing, but many pathogens can bypass these methods. Water filters vary in ability to filter microorganisms according to make and condition. In addition, the survivor would require special tools or the necessary chemicals.

Without a doubt, boiling (for zero minutes) is the prefered way to destroy disease causing organisms in water.

Just what the doctor ordered. On our expeditions have been lugging around too much extra fuel to heat water to boiling point for ten minutes and more. Fuel is heavy, bulky, and sometimes in short supply. Finally there is an article on the internet showing how long it needs to boil! ZERO MINUTES! Bravo. Great site BTW.

Finally some people who agree with me. We don't cook chicken or pork to 212 degrees. I've been saying this for years. Thanks for the reference.

We draw water from a 100' abanndoned mineshaft into our cabin as a water system and just had it tested by health department. They recommended a 5 minute boil. I figured it was way too long, Your information on boiling water makes more sense and settles the issue for us, Thanks.

I have always boiled my water and allowed it to cool before drinking. Some say boiled water has a higher concentration of lead, is this true?

This may be good as a rule of thumb, but other factors are involved, including the atmospheric pressure and ambient temperature, the volume of water to boil, the surface area exposed to the container the area of container exposed to fire, the conductivity of the container and the type and amount of fuel (to name a few!). To use an extreme example, a teaspoonful of water over a propane torch atop Everest would boil instantaneously and cool just as fast - not long enough to do the trick.

Survival Topics Admin - you can always find exceptions in extreme and unrealistic cases. The fact remains, the water is made safe to drink as soon as, and actually before, it reaches a boil.

This is very interesting, I am doing a school science project on this!

I never knew so much firewood was used to boil water throughout the world. I hope this article will teach people they do not need to use as much energy as they thought in order to heat water to make it safe to drink.

Great survival website by the way!

Great article, I came across it through googling how long to boil water. I have friends in third world countries that were finding bottled water expensive. I was recommending simply boiling water and wanted to find out how long to recommend. Believe me, there is a much higher chance they'll follow my 'boil water' advice knowing they just need to bring it to a boil, than to boil for even 5 minutes. Fuel, even wood is expensive, all too often economics wins out to safety. Great information.

Yes, I always figured the times for boiling water were a bit "OFF".

I've always only brorught the water to a boil, then cooled it off. Here In Arizona, if you boiled your water for any real length of time, say 5-10 minutes, you'd have a TOXIC mess of a soup. The water here is bad enough and leaves a white residue not unlike an alkali pond! Try drinking that after "concentrating" those minerals!

I'd almost bet that the water here would be enough to make you either very ill.  Stick with what works!

This is a great survival site you have here. I have some questions that may also hlep address concerns brought up here:

As for chemical pollution that exists in water regardless of temperature, couldn't you get out at least some pollution by running water through a layered filter of charcoal, pebbles, and sand before boiling? I have read that gas masks use charcoal filters for gas pollutants, so wouldn't it work with water as well?

As for wasting fuel, couldn't you also have your food cooking on the side while heating the water? Or use the flame for making scrape-and-burn bowls or making jerky or any other number of uses? Where is it written that fire can only have one application at a time?

Survival Topics - Charcoal, and especially activated charcoal, can help remove chemical pollution from water. As can sand and the like. However not all impurities can removed in this way so you need to be very careful. Distilliing is an option that may also work well in some situations.

You are correct; you can boil water while you are cooking food so that the heat does double duty.

Thank you for telling me what I already thought! I love how common sense beats all those theoretical ideas! We should all just keep things simple! Safe drinking!

Very interesting. I learned something today that I didn't know before!!! Thanks!

Water is hotter at the point just before it boils. It is cooler when it is bubbling and boiling.  Great information about boiling water. Like your survival website very much. Your information is more thorough that most sites I have visited regarding survival.  In the very near future we may all have to have these skills to survive.

I thought you don't need to boil tap water since it's safe already?

Survival Topics - tap water is not always safe to drink, especially during "boil water" advisories.

How about using one of those hanging 5-gallon type shower bags that heat water using the sun.  Will they get the water hot enough to make it safe for drinking?

Survival Topics - as long as the temperature of the water reaches the point of pasteurization which is about 160° F (70° C) for at least 30-minutes the water will be rendered safe from pathogens.  If the bag can get the temperature to 185° F (85° C) it would take just several minute.

Always thought boiling water for 1 minute was the norm. But zero minutes is better, What about chlorine? I know it would evaporate overnight, but will just geting water to boiling point do the same?

Survival Topics - chlorine has the disadvantage of not having a long shelf life since it degrades into salt and water.  In addition, chlorine does not destroy all types of disease causing organisms.

Just a short reminder that water being heated in covered pots and pans boils faster with less fuel and steam loss than those that are left uncovered.

I have always wonderd how long to boil water to kill bacteria

How about Chlorine Dioxide (as opposed to just plain Chlorine)? I've always used AquaMira drops (though there are others, including KlearWater/Xinix solution and MicroPur tablets) with a coffee filter first for long (or short) trips, which I've understood to treat most everything but chemicals, is very light weight and easy to carry (unlike extra fuel for boiling water when in an area where fires aren't allowed).

Very useful and timely article. You cleared a few points with logical explanation and saved me scarce resources in a economically poor country. Thank you!

Ron, great article, and thanks for confirming my suspicions! A brief not re distillation of water. Drinking distilled water will leach minerals from your body. If done for a prolonged period, it will cause a number of bad health problems.

I want to use my water right away , while still hot, for coffee and tea.  Do i still need to allow the water to cool for the pathogens to be destroyed, or can i use it right away?

Survival Topics - as soon as the water reaches the boiling point you know the pathogens have been destroyed or rendered inert (it actually happens at a lower temperature but, lacking a thermometer, boiling is proof that the water has become hot enough).  Of course, you do not want to drink the water boiling hot.

Excellent article, you are indeed correct. However, if I may, I could perhaps shed some light on why most public health authorities and others continue to disseminate the myth that water should be boiled for a greater length of time. It is quite simple: many, perhaps most people do not understand when water has actually reached a full rolling boil. As soon as they see a little bit of bubbles, they mistakenly believe that this means the water is boiling, which is of course false. Hence, for this reason, as a safety precaution, people are often told to boil water longer than is actually required, in the hopes this will ensure they reach the boiling point. But your article is entirely correct and accurate. Well done.

I'm not scientist, but I've always thought this: If water changes from a liquid to a gas at the boiling point then anything with a membrane (bacteria, virus, etc.) will have its membrane ruptured, rendering it inert. Even though not all the water is changing to a gas (otherwise there wouldn't be any water left to drink), the water inside the microbe is at a higher pressure because it is contained, the same as you can build up pressure in a pressure cooker because its contained. The liquid water contained within the membrane turns to steam, destroying the membrane and producing safe water.

And let us not forget the "boil it twice" crowd.

Getting the water to a boil is all you need. Not 1 minute, not 3 minutes, not 10 minutes. I trust the CDC and the EPA about as much as I trust any government agency.