Everything You Need To Know About Purifying Water


One thing that gets hammered into your skull as a budding survivalist is the importance of water. Water is crucial for your body to maintain it’s processes and without it you will die. It’s that simple. So how do you go about securing this resource when the water stops coming out of the pipes or if you’re lost in the wilderness? How do you go about purifying the water so you don’t shit yourself silly from a virus strain or other waterborne pathogen?

What’s lurking in the water?

Water that has been contaminated with either human or animal waste is a breeding ground for harmful bacteria, protozoa and viruses. These microbes wreak havoc on your intestinal system and the body reacts explosively with diarrhea that serves to further dehydrate you. Here are a few examples of the type of pathogens I’m talking about:


Your garden variety protozoa
Your garden variety protozoa

I don’t know about you but I don’t like the sound of this already. Protozoa is an enteric pathogen that relies on water and thrives in fresh water environments. Even more terrifying than the name is the typical life cycle of this pathogen. The protozoan oocysts (eggs) enter your body where they hatch open inside your intestines and begin furiously reproducing. Symptoms of infection begin roughly two days after exposure and include diarrhea, vomiting and intestinal discomfort. Some protozoa are ultra-resilient and resist treatment from chemicals like chlorine (water parks anyone?)  Symptoms can be treated but are generally not unless you have a more serious infection. Expect to ride this one out for 1 – 6 weeks.


Bacteria is structurally distinct from protozoa so it’s grouped into a completely different class of pathogen. Everybody has heard of the heavy hitting bacteria E. Coli and Salmonella. Creeks, rivers, and streams are fertile breeding grounds for these microbes. Symptoms from ingesting bacteria riddled water appear anywhere from a few days to a few weeks and include diarrhea and intestinal discomfort.


Like protozoa and bacteria, viruses are born from the ripe environment found in human and animal fecal matter. Viruses like hepatits A, otavirus, enterovirus and norovirus are some of the more common viruses waiting patiently for a host to infect. Viruses love cold water but disintegrate when exposed to UV light or intense heat. Viruses are structurally smaller than protozoa and bacteria which makes them resistant to filtering devices.

[c5ab_box title=”Note:” type=”alert-info” ]Viruses are rarely found in North American rivers and streams.[/c5ab_box]

4 Ways To Purify Water

I have some good news: Despite all this doom and gloom it is very rare to die from a waterborne bacterial, protozoan or virus infection. Those most at risk for serious health issues include individuals with immune disorders. In a survival situation, however, it is possible that due to the diarrhea you will become dehydrated to a very severe point. Let’s not take that gamble and learn about 4 ways you can purify water.


Filtering dubious water sources is the most popular method of purifying water. Water filters like the Sawyer Squeeze can filter up to a 100,000 gallons of water and remove harmful bacteria and protozoa down to 0.1 microns. Water filters work by filtering the water through a layer of fine porous material. This material allows water to pass but traps anything larger than 0.1 microns – the size of most harmful bacteria and protozoans. Filters can’t remove viruses however because of their microscopic size. Filtering water is a fast, lightweight and convenient method to obtain drinkable water in most locations.

The Sawyer water filter is the standard for filtering dubious water sources

Chemical Treatment

Treating water with chemicals like iodine is another effective way to remove protozoa, bacteria AND viruses. Iodine purifies water by oxidizing the membranes and organelles of water-born pathogens, upsetting their biological functions and causing them to die. Iodine tablets are extremely cheap, effective and lightweight. Downsides of using iodine include a long wait time for purification (up to half an hour) and a less than pleasant after taste. Iodine tablets also don’t keep their shelf life as long as other methods and their effectiveness degrades when exposed to heat, moisture and humidity.

[c5ab_box title=”Note:” type=”alert-info” ]Pregnant women and individuals with a thyroid condition should not drink iodine treated water.[/c5ab_box]

Ultraviolet Light

UV light destroys protozoa, bacteria and viruses by destroying their DNA. UV light can rapidly treat 32 oz of water in 90 seconds. Downsides of using a UV light solution include a reliance on batteries which can die and a requirement for a clear water source. If you have cloudy water the light cannot fully pass through. Finding clear water is essential when using UV light.

One of my favorite hi-tech methods to purify water.


The classic method that never fails. Intense heat structurally destroys the pathogens rendering them inactive. Bring your water to a rolling boil for one minute. If you are above 5000 feet elevation the EPA recommends you boil the water for 3 minutes. This method is effective but very slow and inefficient.

General Rules of Thumb

High elevation streams can be safe sources of water
High elevation streams can be safe sources of water

Firstly, I wouldn’t trust any water source in an urban environment unless it’s coming out of the pipes. (Depending on the scenario even this water might not be trustworthy.) Standing or flowing water next to any city is sure to be polluted with all kinds of pathogens from years of industry. You MUST purify this water. The rules in the wild change. As you go deeper into the wild, water sources become safer. If you must drink water and you don’t have a method of filtering try to find a water source that doesn’t appear to be frequented by humans or animals. Higher elevation water sources are safer because this water is closer to the source and hasn’t flowed far enough to pick up contaminants. Springs are the best because they are the literal source of the water. High elevation streams are a good second choice and still-standing lakes and ponds are a last resort because stagnant water is a breeding ground for bacteria.

Final Thoughts

I recommend that you pick a method of purification and immediately include the appropriate gear in your survival kit. It wouldn’t be a bad idea to include multiple methods. If you have a cook kit you already have a method of boiling water. Pairing this with a bottle of cheap iodine tablets and a water filter will give you redundancy and a more versatile kit. Don’t drink bad water if you don’t have to.

Leave a comment below and share your own thoughts on purifying and drinking water.

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