How Long Does Water Need to Boil to Kill Bacteria?


When going camping (or any other outdoor activity), it is prevalent to get stuck without water – not only it is heavy to carry too much of it, quite often we miscalculate the needed amount and realize the mistake only when it is too late. If you have come to this article, you probably know that one way to purify water is by heating it to the right temperature for the right amount of time. Although, that pops up the inevitable question – how long does water need to boil to kill bacteria, viruses, and protozoa, which are dangerous for human health?

To kill bacteria, you have to boil the water (212°F/100°C) for at least 10 minutes – that would eliminate the vast majority of it, along with viruses and protozoa. 

The exact amount of time and temperature mainly depends on the pathogen characteristics which differs between species – I will show you a summarized table later on in this article.

How Does Boiled Water Kill The Bacteria & Viruses?

To understand how long it takes for boiled water to kill bacteria, I believe it is essential to know what the process actually does to the pathogens.

A common misconception is that the high temperature ends up with an entirely sterile environment; however, that is partially true. Sterilization means that all the harming pollutant get killed, although the more accurate term for the process is pasteurization, which means that only the pathogens which can harm humans are removed.

Boiled water kills bacteria, viruses, and protozoa by changing their proteins configuration, ending up with denaturation. By ruining their membrane and enzymes, you neutralize their ability to cause disease and be lethal. 

Still, the efficiency of pasteurization depends on the time the water was boiling. For example, milk has to reach 149°F/65°C for 30 seconds so you can drink it safely.

How Long Should I Boil The Water?

As an established data resource, I went to check the literature on travel medicine so that I can provide you with the most accurate information. An interesting study I came across was conducted in 2002 and published in the official journal ‘Clinical Infectious Diseases.’

The article gathered data from ten different ones and mentioned the time and temperature it takes to kill different kinds of bacteria and viruses:

Charles D. Ericsson, Robert Steffen, Howard Backer; Water Disinfection for International and Wilderness Travelers, Clinical Infectious Diseases, Volume 34, Issue 3, 1 February 2002, Pages 355–364, https://doi.org/10.1086/324747

As you may infer from the table above, you should boil the water for at least 10 minutes to kill the common bacteria and viruses which could harm humans (assuming that boiled water reach 212°F/100°C). 

Later on, I will describe some other ways to disinfect water, although I believe that heating water features some advantages you should consider.

First, the boiling process doesn’t require you to add any powders or chemicals and therefore regarded as safe and maintains the natural water taste. Also, heating water is a single process which can be done quite fast and pretty much anywhere – no exaggerated preparations need to be done.

How Can I Know if The Temperature is High Enough?

Assuming that the data above is accurate, one has to boil the water for at least 10 minutes so he can drink it safely. Although, how can you possibly know if the water is boiling? The exact point is hard to distinguish when you go camping and not using electrical products like a kettle.

The first thing that is going to happen when you heat water is the formation of little bubbles at the bottom and a whispery sound coming out of your pit – at this point, the water is NOT boiling. 

These bubbles contain oxygen which has been dissolved in the water beforehand. When the temperature begins to raise the oxygen can no longer stay in between the water molecules and unify into bubbles.

The roaring sound is due to collapsing bubbles which formed at the hot bottom, although they couldn’t reach the cooler top. Only when there is a reduction in noise and the water feature the known gentle splashing – you can be sure that the water is boiling.

What Percentage of Bacteria Dies When The Water Boils?

So you’ve heated the water to the boiling point and waited about 10 minutes. Now, pops up the question which asks how efficient that process has actually been.

Well, according to the World Health Organization (WHO), heating water kills bacteria, viruses, and protozoa in different percentages and temperatures.

Bacteria have been shown to be the most sensitive and die relatively fast – a reduction of 90% can be achieved in 1 minute at 65°C. Viruses are a little harder to kill, and most of them die between 60°C and 65°C. Although, as the investigators heated the water even more, to 70°C, there was a 99.999% reduction in poliovirus and hepatitis A virus. 

Protozoa were the hardest to kill and stop functioning once temperatures reach 70°C and more. Is it possible to purify the water entirely by boiling it? Well, probably not.

Nevertheless, when the water reaches 100°C, which is its boiling point, it would most likely go under pasteurization and eliminate all the pathogens which could harm you.

Will Boiling be Enough to Decontaminate Pathogens & Toxins?

As I’ve said earlier, boiling the water wouldn’t eliminate all existing pathogens – otherwise, the process would have been called sterilization instead of pasteurization.

Nevertheless, the water could still be safe to drink if the pathogens it contains are not waterborne enteric (intestinal) pathogens. In other words, if the water contains bacteria, viruses or protozoa which do not harm the digestive system – it will be okay to drink it. 

For example, Clostridium spores could survive boiled water (100°C); however, they do not interact with your intestine cells and wouldn’t do any harm.

Hence, the answer to that question is yes – boiling the water would be enough for decontamination – as long as they reach the right temperatures (as discussed above).

How Else Can I Purify Water?

Let’s say you are seeking a different way to purify water other than boiling – perhaps you don’t have the right equipment or enough time. For that, I decided to add a separate section in this article which will discuss other methods to clean up your drinking water.

Filtration

My favorite way for water filtration is using a water bottle which features the specific mechanism for bacteria and viruses removal – like this one from Amazon (affiliate link).

The advantages here is that you don’t have to trouble yourself by adding supplements to your drink, build a campfire or waste cooking stoves gasoline.

Still, I would choose the drinking water from water sources which are reasonably safe – water taps along the way, for example. I would avoid filling it from sources which contain standing water, like paddles or lakes – you can never know if the filter would purify all the existing pathogens.

Purification Drops

If you don’t mind adding supplements to your drink – you may use purification tablets that dissolve and kill pathogens. One of the most popular would probably be Aquatabs which, according to their manufacture; “kill microorganisms in water to prevent cholera, typhoid, dysentery, and other water-borne diseases.”

Frankly, I’ve never used these before, although the World Health Organization has approved the tablets for emergency cases and continuous use in households – sounds like there is no harm by having these in your backpack.

For more information on purifying water techniques, please check out the following video by Dr. Anja Whittington – she does talk about these two methods and offers a few more. Also, she explains briefly what are the risks in drinking untreated water and what effects it could have on your body. 

How Should I Cool The Water Down?

So you’ve decided to boil the water to kill bacteria, waited about 10 minutes and now finally ready to use it for cooking or drinking. To make it efficient, I suggest that you don’t take any means to haste the chilling process. 

The reason for that is that the longer the pathogens are exposed to heat, the more it is likely they will go denaturation – I suggest that you keep it as it is and let the colder environment do its thing.

Also, if you decide to overcome the long process by adding ice, you should consider that the cubes themselves could be contaminated. As I will explain later on, low temperature doesn’t have the same impact on bacteria as high ones, and in this case, it is better to be patient.

Will The Same Thing Happen in Frozen Water?

Let’s say you are camping with a cooler to keep your drinks chilled on a hot summer day. It is natural to think that an organism wouldn’t be able to survive in such low temperatures since they are so not tolerated for humans.

Still, the bacteria could survive in ice – it wouldn’t be activated, although the low temperatures wouldn’t kill it. I’ve been discussing that topic in my article regarding the question – is it better to drain water from a cooler? 

If you haven’t read it – I highly suggest you will; I’ve spent hours going through the pros and cons for it and offered my personal verdict. 

In short, one of the disadvantages in keeping the water in is that they get contaminated the longer we put our hands in there to get ourselves a drink.

When it comes to eliminating bacteria, viruses, and protozoa – there is no alternative for boiling when trying to face the issue from the temperatures’ angle.

What About Lake Swimming?

Lake swimming could be tempting when you go camping and spend some fabulous time with your friends and family. In general, most cases end well, and you don’t catch and disease – although some pathogens could harm you and sometimes be lethal.

Schistosomiasis

Schistosomiasis occurs when you are swimming in water which has been exposed to freshwater snails which carry that particular parasite.

If the name doesn’t ring a bell, I would like you to know that the disease harms approximately 200 million people a year worldwide. The parasite gets into your system through the skin and most commonly cause rash, fever and muscle aches which could exist years when untreated.

Brain-Eating Ameba

If the name Naegleria fowleri doesn’t scare you, I bet the title does. When swimming in water that contains the ameba, it could get into the brain through your nose and the Olfactory cranial nerve.

In opposed to the previous one, the brain-eating ameba is a much rarer phenomenon, and only 34 cases have been recorded in the past ten years. However, of those who have been attacked – only one survived.

Legionella

If you’ve encountered a poorly maintained hot tub, there is a good chance you were exposed to Legionella. While most people come across it and develop no response – in some cases, it may cause atypical pneumonia which features coughs, shortness of breath, high fever, aches and more.

The bacteria would most probably be found in medium-hot water containers and can be sometimes found in drink water and requires pasteurization.

These examples are merely a few, although they shed a different light on swimming in lakes haven’t been purified. I wouldn’t say you should entirely avoid lake swimming – camping should be fun after all. Still, if you feel any symptoms afterward – please appoint immediately to your doctor – just in case.

Conclusions

Boiling the water is one of the most common techniques to kill bacteria and other pathogens and to get the best efficiency you should keep it heated for at least 10 minutes.

If you do it, you will probably kill more than 90% of bacteria and around 100% of harmful viruses. That process isn’t sterilization – some pathogens will still survive, although they don’t cause water-borne diseases (which means they do not harm when drinking them).

You shouldn’t underestimate contaminated water – as I’ve shown above, sometimes it may contain some dangerous bacteria and amebas. If you don’t have the right equipment to boil your water (or perhaps you ran out of it) – you can use tap water along the way and purify it by filtered bottles or purification tablets.

I hope my article has answered your question and provided you with some additional points of view. If you have any hanging questions, or perhaps new insights, let me know all about them by leaving a comment below!

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