How Long Do You REALLY Have to Boil Water Before It’s Safe to Drink?

The REAL Answer Is Likely Going To Surprise You!

So what’s your best guess? How long do you really have to boil water before it’s safe to drink?

A) 5 minutes?
B) 10 minutes?
C) 20 minutes?
D) 30 minutes?

The correct answer:

If you actually saw through our trick question and guessed 0 minutes, you would be correct!!


Now you might be thinking, “Now wait just a minute… how is that possible?? That’s not what I learned on Survivorman or Man vs. Wild!”

Well, as you are about to learn… not everything you see on TV is true (Shocker, right??). And it’s absolutely, positively & definitively 100% possible to purify water without boiling… with just a little know how!

Now there’s a lot of conflicting information out there regarding how to “purify” water to make it safe to drink, and it can get pretty confusing. There are chemical treatments, filters and of course the “old faithful” boiling of your water to make it safe to drink. Most of these treatments are perfectly viable for making water drinkable as long as you understand them properly and truly know the limitations of each of these methods.

For this article we are going to stay away from the chemical and filtration methods of water purification and focus primarily on using heat to treat water and make it drinkable. Heat is a fairly effective method for treating water because it eliminates (kills) the microscopic organisms that are living in that water that can make you very sick.

OK, so how much heat? And for how long?

Great questions! Depending on your source of information, “conventional wisdom” has told us for decades that bringing water to a rolling boil at the very minimum and holding it there for a period of time is what is required to kill these microscopic pathogens.

For example, let’s take a look at what the Boy Scouts of America say about treating water:

“The surest means of making your drinking water safe is to heat it to a rolling boil—when bubbles a half inch in diameter rise from the bottom of the pot. While this is a simple method, it does require time and fuel.”

Now let’s take a look at what the United States Marine Corp. recommends for treating water:

“Purify all water obtained from natural sources by using iodine tablets, bleach, or boiling for 5 minutes.

Boiling Water For Survival - Is It Really Necessary?

OK, so… if you can purify water without boiling, are the Boy Scouts of America and the Marines wrong? Technically, no. Bringing your water to a full boil will absolutely kill all common pathogens that we have all learned to take so seriously because can make us sick with illnesses like Giardia, Cryptosporidium, E. coli and the rest.

The problem with bringing your water to a full boil, as you are about to learn, is that doing so is actually complete overkill when it comes to treating water for harmful microbes! Boiling your water, while completely safe and will absolutely kill those nasty pathogens, is actually not necessary and could be a complete waste of precious fuel in a survival situation!

OK, so how much fuel are you wasting exactly?

Did you know that the amount of fuel/energy required to heat water to 200° F… it takes that SAME AMOUNT of fuel AGAIN to take that 200° water up to 212° F!!! Just for that last extra 12° to get your water to it’s actual boiling point!! Yes, just to be 100% clear, those last 12° actually require TWICE as much fuel as it does just to get your water to that initial 200°!! TWICE as much fuel! That is nothing to scoff at!!

Bringing Water To A Full Boil To Drink On A Gas Stove Is A Complete Waste Of Fuel!


Now this may not matter if you have a fire going and are surrounded by tons of fire wood, but I caution you not to foolishly dismiss this bit of  information too quickly. Take a moment to pause and THINK about the implications of this information. There are legitimate survival situations where this knowledge could ABSOLUTELY matter. What if you are in a situation where making a fire is not practical/possible or your options for containers to boil in are limited? In these types of applications, then this knowledge could absolutely matter (we are going to give you some specific examples of these types of scenarios later in the article)!!

What SCIENCE Says!:

So now that we know what the Boy Scouts of America and the Marines say about purifying water (and we love both of these organizations!), but let’s take a look at what science tells us about using heat to purify water.

Important Temperatures to Factor In to this Equation:

212° F = Temperature at which water boils
160° F = Temperature at which milk is generally pasteurized
149° F = Temperature at which Hepatitis A is quickly killed
140° F = Temperature at which bacteria (V. cholerae, E. coli and Salmonella typhi) and Rotavirus are quickly killed
131° F = Temperature at which worms & protazoa cysts (Giardia, Cryptosporidium and Entamoeba) are quickly killed

As you can see from the temperatures listed above, the pathogens that we are primarily concerned about when it comes to safe drinking water are ALL killed (immediately) at temperatures much lower than 212°, the temperature at which water boils. Just look at those temperatures indicated in red in particular. That being the case… why would you unnecessarily waste any more fuel than you need to heating up your water those additional 63°?? Or why would you necessarily allow the fact that your water didn’t exactly come to a rolling boil prevent you from hydrating with said water if you know for a fact that it is 100% free of biological pathogens based on science? Great questions, right?

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Now let’s take a closer look at that milk pasteurization temperature above (in orange): 160° F. This is the FDA approved temperature utilized to safely “burn off” pathogens from milk so that we can safely purchase it from the local grocery and consume it. Do you see the significance of that temperature?

Pasteurization is a process invented by French scientist Louis Pasteur during the early nineteenth century. Pasteur discovered that the pasteurization process made it possible to heat the milk to high enough temperature to kill all harmful microorganisms without “cooking” the milk causing it to curdle.

Now of course you never have to worry about your water curdling, but an important lesson can be gleaned from this milk pasteurization process that can be extremely beneficial: Water, like milk, does not have to be boiled to be safe to drink!!

Pasteurization is a process that uses heat to disinfect liquids and kill microorganisms without bringing those liquids to a full boil as boiling liquids like milk completely ruins them. And you can actually pasteurize water at even lower temps than 160° if you do it for a longer duration. This is extremely helpful in situations where A) you aren’t able to produce fire for heating your water, or B) you can make fire but you do not have a suitable container for boiling that can withstand the intense heat of your fire.

Lower temperature/longer duration pasteurization can actually be done with discarded plastic 2 liter bottles set in the sunlight for longer periods of time (typically 6 hours). This method of disinfecting water is known as the SODIS (Solar Water Disinfection) method. Let’s take a closer look at the SODIS method for purifying water so you have another great water treatment method to add to your survival knowledge and skill sets!!:

The SODIS Method For Disinfecting Water!

The SODIS method for disinfecting water is similar to pasteurization, but there are some significant differences between SODIS and pasteurization. SODIS stands for Solar Disinfection Water Purification and, unlike boiling and pasteurization, SODIS does not rely entirely on heat to disinfect water. While temperature is a variable in the SODIS equation, temperatures achieved in the SODIS method are much lower than what is required even for pasteurization! This is because SODIS relies more on exposing the water to intense UV light (direct sunlight) and a longer period of time to kill off pathogens. As I indicated previously, it is recommended that the SODIS method occurs over a minimum duration of 6 hours.

Temperature & UV Light + Time = SODIS 

The SODIS method  can be expedited with a couple of simple tricks if need be: A popular enhancement to the SODIS method is to place your clear bottles of water on a reflective or heat absorbent surface like an asphalt roof. You could also put aluminum foil, a mylar blanket to reflect the sunlight back through your bottles of water or leverage a black plastic bag or drum linger under your bottles to absorb more heat. Another trick some people use to speed up the process is to spray paint the back side of the bottles with black paint or cover it with black tape. Again, this black surface absorbs more heat. But you don’t want to necessarily cover your entire bottle in black as this would prevent UV light from passing through your water and this UV light is an important part of killing those pathogens.

A great example of a survival situation where the SODIS method could prove vital is if you were stranded on a tropical beach where plastic bottles had washed up but starting a fire is proving difficult because of the lack of good fire materials, fire starting implements, and/or humidity. Setting several clear two liter bottles full of water (fresh water, obviously) out in the sun for several hours. Placing them in the hot sand would also be helpful.

Another terrific example of SODIS occurring naturally would be finding a concavity in a large rock that had collected rain water and had been sitting in the sun for hours. This would be a MUCH better option in terms of choice of a water source over a creek, stream, river or lake where animals will have more likely contaminated those water sources. The sun would have a much better chance of having “burned off” any pathogens in this isolated pocket of water. That right there, my friends, is SODIS occurring naturally in the wild!!

So Why Do So Many “Survival Experts” Advocate That We All Boil Our Water?

Great question with a very simple answer: When those bubbles start to roll in your container of water, that is nothing more than a clear and effective VISUAL INDICATOR/CONFIRMATION that your water has become hot enough (actually MORE than hot enough) to have killed all of those little nasties. It works. It’s effective. But is it necessary? Is it always ideal? Is it always possible? Or would it be handy to be a bit more informed and realize that there are additional ways to treat water in a survival situation that don’t require a fire and/or metal container suitable for boiling?

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Why Not Just Boil To Be Safe?

Many of our readers have actually foolishly scoffed at the insight I am sharing with you now regarding not having to boil to purify water because they simply fail to imagine survival scenarios where you wouldn’t have a proper metal container for boiling water or you can’t build a fire (either because of environmental conditions or because of threats). If you have a metal container and can make a fire, then absolutely boil away!! 

But what if you have neither? What then? Wouldn’t it be nice to be able to hydrate in a survival situation without either? Wouldn’t it be nice to not have to depend on either of these variables if you were in a situation where you had neither?

Let’s take a closer look at some scenarios where boiling water to purify it is NOT the best idea:

1) When you are using a gas stove (finite fuel resources that you don’t want to waste)
2) When your only option for a container is one that is not a heat resistant container (plastic, Lexan, wood, or other limited use materials)
3) When fire is not an option (can’t start because of conditions, fire/smoke could reveal your location, etc.)

Boiling Water To Purify It For Survival Hydration Is Not Always The Best Idea And Completely Unnecessary!


Your Pasteurization Friend: the WAPI!

So if the bubbles from boiling water gives us that terrific visual indicator to let us know that our water has reached 212° F… but now we know that boiling our water to make it safe to drink is actually a waste of precious fuel resources (fuel, wood, candles, etc.)… how can we then determine if our water has gotten hot enough to have been properly pasteurized without those rolling bubbles? Great question again! We could certainly use a thermometer… but most of these are glass and very fragile. Too fragile to keep from breaking inside your kit. We need something small, light, compact, durable and can be used over and over again to let us know that our water has reached that effective pasteurization temperature.

SOLUTION: A tiny inexpensive device known as a Water Pasteurization Indicator (WAPI)!

WAPI’s are incredibly simple little devices. They are nothing more than a tiny sealed clear tube with a special brightly colored (easy to see) green wax inside of them. This wax (known as Myverol 18-06) is formulated to melt at just the right temperature for pasteurization (156° F or 69° C.). In most WAPI designs the tube typically slides up and down a thin cable with a tiny weight on each end allowing you to flip the tube so that the wax inside can be easily positioned at the top of the tube again.

To use your WAPI simply slide the little tube down to the bottom of the wire so that the wax-heavy end of the tube is oriented toward the top of the tube. Place your WAPI tube into your container of water draping the weight at the opposite end of your WAPI tube over the lip of your container so that it is easy to grab. Once your water has reached pasteurization temperature of 156°, the wax in your WAPI tube will start to melt allowing it to fall from the top of your clear tube to the bottom of your tube with a little help from gravity. This is your visual indicator that your water has been pasteurized!

While WAPI’s are extremely inexpensive to purchase (typically under $10), it is possible to make your own WAPI! We have even seen versions made from drinking straws and glue sticks for hot glue guns. While you can make your own WAPI, they are so inexpensive that we recommend purchasing one. “Quality control” can be an issue with DIY WAPI’s causing inconsistent results… even when purchasing DIY kits made with genuine parts. Sometimes it’s just best to leave work like this to the experts… especially when a piece of kit like this is so inexpensive to begin with.

Get your own Water Pasteurization Indicators (WAPI) here!


When traveling to countries that are known to have a questionable water supply (due to harmful pathogens remaining in the water supply), one little known trick when you cannot access bottled water is to pour yourself a glass of HOT water from the tap instead of cold. Water from a hot water heater has actually been pasteurized! Water from hot water heaters is typically between 120° F and 140° which is slightly below ideal pasteurization temperatures… but remember that heat + time = pasteurization! 99.999% of water borne pathogens are killed instantly when water is brought to 149° F. The same result can be accomplished with lower temperatures if you simply allow the water to remain at that temperature for a longer period of time. For example, water can be pasteurized at 130° F if simply held at that temperature for 2 hours.


As with anything else, use common sense when treating water. Your health and potentially your life are on the line. When in doubt, heat your water a little hotter or for a little longer. It can’t hurt unless fuel is at an absolute premium. Use your best judgement!

Just like with boiling, pasteurizing is not a panacea for making any water drinkable. Boiling and pasteurizing only take care of a single threat that can be present in potential drinking water: biological pathogens. But biological pathogens are NOT the only health threats frequently found in “wild water”. For example, pasteurizing sea water will not make it drinkable as pasteurization does not remove the salts from sea water. Just like boiling, pasteurization only kills microorganisms that can make you sick. It does not remove salt, chemicals, metals, pollutants or other toxins that could harm you from your water for you. It’s extremely important that you understand this!

One example in particular that comes to mind where both boiling and pasteurizing water can make matters worse for you instead of better is in the case of the recent algae blooms in the Toledo area. Water of this type contains the toxin known as microcystis aeruginosa. Microcystis aeruginose is a species of freshwater cyanobacteria which can form harmful algae blooms (HABs) in fresh bodies of water. Boiling or pasteurizing water of this type actually INCREASES the presence of the toxins and makes your water more toxic to drink!

So when it comes to treating water to make it drinkable, be smart. Be careful. Play it safe. Use your noggin.

Happy pasteurizing and safe hydrating!

Want to learn more about Water Pasteurization? Check out our Water Pasteurization Pinterest Board!:

Follow EQUIP2SURVIVE’s Water Pasteurization board on Pinterest.

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Author: Josh Nieten

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    • Thanks so much Shaun! And thanks for taking the time to read it! The more you know, right?? 😉

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  1. I think you gave all survivalist a good lesson on other methods to obtain ways to try in a adverse situation if 160 and above is more than adequate to drink like you say us your noggin Thanks for the heads up.

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  2. I live in a questionable water source area. This is a big help for me. Thank you

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  3. As a fire dep’t infection control officer, I know and appreciate the facts behind this article and I’m very glad to see it out there in public, finally.
    One additional but huge detail on the spent fuel – taking a liquid at 212F to rolling boiling or vapor(steam) phase involves a load of latent heat, much much more than just increasing 60 degrees. I forget the math, but it’s thousands n thousands of btu’s.
    “Boil 5 minutes” is germ killing for dummies. Pasteurization has been effective and unchanged for generations – it works, or it wouldn’t have passed the test of time.

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