Boiling water is one of the oldest water purification methods, but how effective is boiling water. Does it really kill all bacteria, protozoa, viruses, and every other water born illness? How long do you have to boil it and can anything survive the extreme heat of a steady boil? That leads to a very important question: Can bacteria survive boiling water?
Yes there are some types of bacteria that can survive a short stint of boiling water, but prolonged boils will kill them. Reaching a steady boil for 2-3 minutes guarantees any waterborne bacteria, viruses, and protozoa will be killed, but that’s usually not necessary. All waterborne pathogens are killed at lower temperatures 140°F-185°F so by time you reach boiling temperatures the water will be safe to drink.
Although some bacteria may survive in boiling water you really shouldn’t worry. Boiling is an extremely effective water treatment method and it will kill the vast majority of water born bacteria, viruses and protozoa. If you’re really worried about killing everything just boil your water for 2-3 minutes and that will take care of everything.
In the rest of this post I’ll give examples of bacterial strains that can survive boiling water and explain how they can survive the extreme temperatures.
How Does Bacteria Survive Boiling Water?
The vast majority of water borne pathogens can’t survive boiling water. All water borne bacteria will slowly start to die once you reach temperatures over 140°F (up to 10 minutes) and quickly die at 185°F (2-3 minutes). Once you reach boiling temperatures 212°F they die within seconds. Notice that as you reach higher temperatures the bacteria will die in a shorter amount of time.
There are some exceptions (non waterborne bacteria) that take longer to kill, but bacteria will always die in extreme heat. That’s why most experts recommend boiling water for 2-3 minutes to make sure all bacteria is killed. This kills all of the common water borne bacteria, protozoa and viruses, but also takes care of the hardier varieties.
I’ll explain a little bit more about this below, but the most common bacteria to survive a boil is Clostridium botulinum. That’s the bacterial strain that causes botulism. Botulism is a rare, but very serious illness so you need to be especially careful when doing activities that could lead to the disease. The most common cause of botulism is improperly canned or fermented foods, people who inject drugs (heroin), and people who drink homemade alcohol that’s not properly sterilized.
Boiling Water To Kill Bacteria
Boiling water to kill bacteria is fairly straightforward. Just fill a pot with sediment free water, bring it up to a rolling boil, and let it cool down to be ingested. I’ll go over each step in detail below.
- Fill Pot With Water: Fill your pot about 2/3 full with water. Overfilling the pot will lead to water splashing out and spillovers once it reaches a rolling boil.
- Place The Pot On The Stove: Place the pot of water on the stove and bring the temperature up to the highest setting (Hi or Max)
- Cover Up The Pot (optional): Covering up the pot with a lid will speed up the boiling process, but this isn’t necessary. I recommend covering the pot if you’re camping or backpacking and working with limited fuel.
- Let The Water Reach A Rolling Boil: Let the water come to a full rolling boil. This is when the bubbles are rapidly breaking the surface. You will start to see bubbles once the water reaches 160°F, but that’s not hot enough to quickly kill bacteria.
- Wait At Least 1 Minute: Most experts recommend waiting at least 1 minute so there’s enough time to kill bacteria that thrives in high temperatures. You need to wait 2-3 minutes if you’re sanitizing canning jars, fermenting equipment, or anything else that will be aged. This guarantees all the bacterial spores will also be killed.
- Let The Water Cool: It will take a long time for water to drop down to room temperature and be safe to drink. Pouring boiling water into a cold glass container can lead to shattering so make sure you wait 5-10 minutes. The same thing can happen if you put hot water into the refrigerator.
- Aerate The Water Before Drinking: Aerating your water before drinking isn’t a safety concern, but it will make boiled water taste better. As you boil water steam gets released into the air making the water taste flat. You can reintroduce air into the water by pouring it back and forth between containers. Pouring the water back and forth from the pot to your storage container a few times will reintroduce air to the water making it taste better.
Why Boil Water If Waterborne Pathogens Are Killed At Lower Temperatures?
The vast majority of water borne pathogens are killed below the optimum boiling temperature. Water boils at 212°F, but you may start to see bubbles rise at 160°F. More than 99.99% of bacteria won’t survive for long above 140°F so why do you need to get to the maximum boiling temperature?
You can technically kill all bacteria by heating water up to 140°F for 10 minutes, but there’s a major problem with that. It’s hard to figure out the temperature just by looking at the water and you would have to wait a long time for the bacteria to die. It’s much safer to aim for a rolling boil so you’re guaranteed to kill everything and you’re not playing the did I wait long enough guessing game.
How Long Should You Boil Water To Kill All Bacteria?
The standard recommendation for purifying drinking water is to wait at least 1 minute after a full rolling boil. That’s enough time to kill almost every type of bacteria. Just understand that those recommendations are solely for purifying drinking water.
If you’re sanitizing canning jars or fermenting equipment you need to boil the items for 2-3 minutes to kill off everything. Botulism is your main worry! Botulism can be deadly and thrives in extreme heat. It takes minutes to kill boiling at 212°F and you can be left with botulism spores if you call off the boiling process early.
Those spores aren’t dangerous if they’re ingested immediately in your drinking water, but they can grow into full sized bacteria over time. Your improperly sanitized home canning equipment is the perfect breeding ground for botulism. Ingesting botulism infected food can lead to serious illness and possibly death.
What Bacteria Can Survive Boiling Water?
The vast majority of bacterias and pathogens are killed in boiling water, but there strains that can survive extreme temperatures. These bacterial strains are known as hyperthermophiles. A hypothermophile is any organism that thrives in extremely hot environments above 140°F.
The main bacterial toxins will die off at high temperatures, but as they’re dying the bacteria will releases spores that can survive at extreme temperatures. Those spores can withstand a rolling 212°F boil for hours at a time and can grow into a very lethal toxin. That’s why most people decide to boil their home canned goods before eating them.
Botulism is by far the most common hyperthermophile bacteria known to cause illness. It’s very common in home canning, fermenting, and among intravenous drug users.
The Causes Of Bacteria and Other Pathogens In Water
Bacteria is extremely common in backcountry water sources, but it can also happen in municipal water supplies. The biggest concern is bacteria that originated in the gut of warm blooded animals like wildlife, pets, and livestock. Animals grow the bacteria in their gut, excrete the bacteria through their feces, and then it gets washed into the surrounding water supply.
There’s no way to get around bacteria in an outdoor water source. All surface water contains some level of bacteria, but underground water should be safe. So every pond, creek, river, and lake is infected with bacteria.
Obviously stagnant water isn’t safe to drink, but you run into the same problems in flowing creeks and rivers. You need to use some type of water filtration method with any backcountry water source. There are easier methods to deal with bacteria, viruses, and protozoa that I’ll get into below.
Filtering and Purifying Water
Most people use the terms filtering and purifying water interchangeably, but there’s a very obvious difference.
- Water Purifiers: Water purifiers work by killing everything in the water including bacteria, viruses, and protozoa. There are multiple ways to purify water but the most common purification methods are heat, chemical, and UV purification. Boiling water is the oldest water purification method, but other options are much easier. Chemical treatments typically use chlorine to treat the water and UV Purifiers use ultraviolet light to kill everything. All of these methods work extremely well and kill everything in the water.
- Water Filters: Water filters run water through a porous filter trapping bacteria, protozoa, microplastics, and sediment in the filter. Notice that I didn’t mention viruses! Viruses are much smaller than bacteria cells so they get through most water filters. There are filters that can handle viruses, but they’re expensive and clog quickly.
If you’re camping or backpacking in the United States you should use some type of water filter. You can boil your water, use chemical treatments, or UV Filters, but there’s rarely viruses in the USA so they’re not necessary. Most people like to run their water through a filter to remove sediment and algae anyway.
Water filters are easy to use and you can clean a lot of water fast. I like the Sawyer Mini Water Filter because it’s cheap and can attach to your water bottle, run inline with a hydration bladder, or be used in a gravity filter setup. Pump style filters like the Katadyn Hiker Pro and MSR MiniWorks will also work, but they’re bulky, expensive, and harder to use.
People that are camping/backpacking outside of the United States need to worry about viruses in their water supply. Boiling water works, but it will use up a lot of fuel. Chemical Treatments (aquatabs) and UV Purifiers (Steripen) are much easier to use. Aquatabs are cheap and easy to use (just drop one in), but it takes 30 minutes to clean your water.
The Steripen is a much easier solution for dealing with viruses. Just set it in your bottle of water, press the button, and wait 30 seconds for safe drinking water. You probably want to run the water through a filter to remove sediment and algae, but that’s not necessary from a safety standpoint.