How to Purify Water in the Wild: Filtration vs. Purification

Purifying water found in the wild enables you to consume it safely, as the purification process eliminates harmful viruses and pathogens that could cause waterborne illnesses. Knowing how to purify water is a valuable skill to learn in the event that you find yourself stranded in a backcountry area because it enables you to stay safely hydrated, which is necessary for your survival.

Always filter your water before purifying or drinking it to remove any errant debris that could cause illnesses.

For safety purposes, beginners and expert outdoors-people should always keep fundamental survival tools on hand, including a compass (or map), knife, fire starter, first-aid kit, water filtration device, and purification tablets (like iodine tablets).

Filtering water is the process of siphoning water through a filtration device to remove debris and bacteria that could cause illness. Standard water filters rely on physical sieve-like tools to remove water impurities.

On the other hand, purifying water involves introducing a chemical or disinfecting element (like UV light or chemical purification tablets) to the harvested water to kill harmful elements like viruses and tiny microorganisms. Water filtration removes many contaminants but doesn’t remove viruses and extra-tiny microbes, which are too small to catch in a typical filter.

Drinking contaminated water can lead to waterborne illnesses like giardia and dysentery, which is why it’s important to purify any water harvested from a wild source. Use UV lights or purification tablets to kill bacteria in their water supply and make it drinkable. Alternatively, use the sun’s ultraviolet (UV) rays to distill your water and eliminate pathogens. Here’s how to purify your wild-harvested drinking water using solar water disinfection:

1. 1. Gather your materials. First, you’ll need a container like a coffee can, glass bottle, stainless-steel pot, or water bottle. The bigger the opening of your container, the better, because you’re going to use it to catch evaporated water. Find a digging implement like a stick, spoon, or trowel to make a hole in the ground and a small pebble or rock to attract condensation. Make sure that you have a piece of plastic, preferably transparent or translucent, to cover the hole you dig. Finally, you’ll need some moist organic material—like plants or moss—to place near your container once it's in the hole.
2. 2. Dig your hole. Find a place with moist soil that gets plenty of sunlight. Use your digging implement to dig a hole in this area. Make the sides even and straight so that it’s easier to maneuver your container in and out of the hole.
3. 3. Place your container. Put your water container in the center of the hole and surround it with moist matter, like moss or plants. The plant material will attract moisture and expedite water evaporation.
4. 4. Cover the hole with plastic. Use plastic to seal the hole’s opening so that evaporating water cannot escape around the sides. The plastic should be translucent enough for light to pass through it. Weigh your plastic tarp down with rocks around its perimeter to keep it taut. The plastic will trap moisture in the hole, creating a mini-greenhouse.
5. 5. Place a pebble on top of the plastic. Use a small rock or pebble to make a slight depression in the center of the plastic; this will create a slanted surface directly above the container that will collect the water. Water will evaporate and collect on the inside of the plastic, then drip down into your container.
   
6. 6. Remove the container from the hole. After collecting enough water in the container, remove it from the hole.
7. 7. Filter your water. Filter your water with a water filtration device to remove any extra debris that may have collected inside the hole. Distilled water will quickly pick up impurities from roof surfaces, leaves, or tree trunks, so it is essential to store distilled water in a clean container directly after distillation. Once you’ve transferred your water to a clean container, it is ready to drink.

If you know how to start a fire, boiling water is an effective water purification method. Boiling will not remove every pollutant from the water but can eliminate parasitic protozoa such as cryptosporidium and giardia. (Water purifier tablets are more effective at doing that, but they can taint the water’s taste.) However, in a severe survival situation where every drop counts, boiling can significantly reduce the amount of water you have to drink.

To purify water via the boiling method, first, start a fire. Next, fill a coffee can or steel pot with water, then place it over the flame until it reaches a rolling boil. Continue to boil the water for at least one minute (or three minutes at elevations of 6,500 feet or more).

Consider the following factors when gathering drinking water from the wild:

1. 1. Animals: If you see animals drinking from a water source, chances are that you can drink from it too. However, it’s essential to avoid water with dead animals or excrement floating in it because these contaminants will likely carry viruses or bacteria. Avoid streams or lodges where beavers live because they can spread giardia.
2. 2. Water color: Clear water does not equal drinkable water, but cloudy water, green water, or floating sediment are clear indicators of contamination. Water tainted with algae or oily films is also not potable. Avoid any water that has a strong odor. If you’re not sure whether the cloudiness in your water is pollution or simply dirt, fill your container and let the water sit for a while to see if any of the debris settles to the bottom. Soil will sink in water.
3. 3. Water source: One of the most critical water purification elements is the water source itself. Fresh water sources, such as rivers, streams, and other sources of moving water, are safe to gather from, while stagnant water is not. (Standing water hosts lots of bacteria.) Gather water from higher elevations as close to the source as possible. Avoid gathering water from animal grazing sites because animals like beavers can spread viruses and bacteria.

Certain outdoor activities carry an elevated risk of serious injury. Wilderness scenarios require extensive survival gear, including but not limited to food, water, maps, protective clothing, and first aid, along with mental and physical fortitude. This article is for educational and informational purposes and is not a substitute for hard skills and expertise.

Prepare for any outdoor journey by grabbing a MasterClass Annual Membership and committing Jessie Krebs’s wilderness survival course to memory. As a former United States Air Force Survival, Evasion, Resistance, and Escape instructor, Jessie can teach you everything you need to know about packing for a trip (neon is the new black), purifying water, foraging (crickets: the other white meat), starting a fire, and signaling for help (forget SOS).