Fresh water is necessary for the survival of all living organisms, and our bodies are composed of 60% water. Securing a fresh water source during any outdoor survival scenario is crucial, and locating a truly ‘potable’ water source is perhaps the most difficult aspect of wilderness survival. I recall wilderness outings where safe natural springs were nowhere to be found and other, more labour intensive, water purification was required to enjoy a safe drink. Join me as we travel off-grid to explore the essentials tips on water purification and filtration.

Waterborne Illnesses

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A condition known as Giardiasis is one I know all too well, and the result of a nasty parasite known as Giardia Lamblia; referred to as “Beaver Fever”.  It is one of most common illnesses from drinking untreated water. Symptoms include stomach cramping and violent diarrhoea. Although Giardia is not lethal, it can increase your likelihood of becoming dehydrated, and simple filtration of clearing debris from your drinking water will not filter-out Beaver Fever. You need to use one of my purification techniques described here below.

Purification VS Filtration

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There is a clear distinction between the purification of drinking water and filtration, as they are not synonymous. Water purification is achieved in 3 ways; by using either ultraviolet light to render bacteria inoperative, chemical additives that purify water, deactivating harmful contaminants or lastly, boiling.

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Water filtration involves the basic straining of debris, sentiment and suspended solids. Depending on which filtration device you make, small amounts of bacteria may also be captured. In some situations both filtration and purification of your survival water may be required. It is essential that every would-be outdoor survivalist understand the difference between the two and the reasoning behind each.

Water Filtration

Water filtration takes care of the protozoa, debris and some bacteria but most of all improves the taste of your water. The average ground water in North America is free of dangerous bacteria, pathogens and basic filtration may be the only process required. That is assuming that your water is free of human and animal waste, with no presence of faecal coliforms. Without laboratory equipment of course, how do you know your water source is indeed safe for consumption? Water purification is a must in any wilderness survival situation!

Water Purification

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The purification process makes water safe to drink by eliminating harmful viruses, pathogens however may not improve the quality of the water as far as taste goes. Dirty water may be purified but still require a filtration process afterwards.

Boiling water

Boiling water is very common and typically the safest purification option. The standard rule for drinking boiled water is ten minutes boiling time regardless of your location above sea level. Typically, less boiling is required at sea level and as the elevation increases, more boiling time is required. Boiling eliminates any chance of contaminants, bacteria, and parasites making the water completely safe for consumption. It does however require fire.

Rock and Sand DIY Filter

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The rock and sand filter is the simplest do it yourself water filtration device available.  This method involves layering of materials in a plastic bottle or even hollow log.  Pour water through the top portion of the filter allowing it to percolate through the layers and create a small hole at the bottom, where you collect the filtered product in a container. Rock and sand filters can made with a piece of fabric or trap. Make sure the bottom is tied off tightly with only a small hole, straw or drain tube inserted for the clean water to drip out.

The Charcoal Filter

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Since charcoal is a natural cleansing agent and often used to filter water, collect as much dry coals from your campfire as possible. Crush them into smaller bits and layer in a bottle or hollow log similar to the rock and sand filter. Similar to the rock and sand filter, water passing through the charcoal bits adds an extra layer of filtration. This process eliminates more impurities in the water including some bacteria.

Iodine tablets


The first water purification option is use of purification tablets. Iodine is the most common purification tool and should be administered as five drops of 2% tincture to an average size canteen of water. If your water appears murky or tannic, ten drops of iodine will do the job.  Always let your water container sit for a few minutes once the iodine has been added.

Chlorine Bleach

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Similar to iodine, bleach can also be used as a purification agent. Make sure the bleach you use has no special cleaners or scents. By adding 1/8 teaspoon of bleach to a gallon of water and letting it sit for one hour, you will purify your water safely for consumption.

Sodium Chlorite 


Similar to bleach, these tablets use chlorination as its method for purification. It is a common method for disinfecting water in public pools by eliminating bacteria cell walls thus killing the organism. As you drink chlorinated water, the chlorine content is neutralized by our system therefore causing no harm to the human digestive system. This solution may be purchased at a survival or camping shop and are easily transportable.

The Life Straw

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The latest product on the market is Life Straw – an extensively tested drinking device proven to remove 99.999% of all contaminants in any water source including all bacteria, chemicals and viruses. I have tried Life Straw myself and can say that the product is convenient and effective. Company representatives were unhand at a Cabela’s store opening a few years ago. They collected water from a puddle in the parking lot and I drank it through the life straw. Not only was the puddle water safe for consumption, it tasted like fresh spring water.  Tested and recommended for Canada and the United States, it is an ideal product for backpacking, hiking and emergency preparedness. One Life Straw can filter up to four thousand litres of contaminated water into safe drinkable water.

Final Words

The Rule of Four says you have about four days to survive without water, but need to make fresh water a priority after fire and shelter, for the simple fact that increased dehydration seriously compromises important body functions. By practising a few of the water purification and filtration techniques outlined, you will be better prepared for wilderness survive situations.

Learn more about wilderness survival in my feature on Essential Fire Making Techniques.