Access to drinking water is often a challenge in emergency situations. In the wilderness or after a disaster, improvising a water filter becomes an essential skill for survival. Fortunately, it is possible to easily create a filter using materials you can find.
How to choose materials for making a water filter?
This is a DIY method that can help in a pinch, but it is limited for long-term crisis situations. You will need good-quality materials.
- An empty plastic bottle of around 2 liters.
- Gravel of different sizes.
- Clean sand.
- Activated charcoal or natural charcoal.
- Fabric, cotton, a bandana, or even a t-shirt.
If you don’t have activated charcoal, we recommend using natural charcoal obtained by burning wood. It must be crushed finely, as it removes some chemical pollutants present in the water. Avoid barbecue charcoal briquettes, as they contain toxic chemicals.
Steps to make your homemade water filter
Prepare the bottle
Take your empty plastic bottle and cut it in half. Keep the upper half (with the neck), as it will form the funnel of the filter. Poke a few small holes in the cap to allow filtered water to flow slowly.
Add the fabric or cotton
Insert a piece of fabric, a folded bandana, or a ball of cotton into the neck of the inverted bottle. This first layer acts as a barrier against the coarsest particles in the water and prevents clogging of the lower layers.
Add activated charcoal
Next, pour a generous layer of crushed activated charcoal. If using natural charcoal, crush it into small pieces about 3 to 5 mm in diameter. This layer is important because it absorbs potentially harmful chemicals in the water and improves its taste.
Add fine sand
On top of the charcoal, add a layer of clean sand. This intermediate layer filters fine particles, sediment, and some microorganisms. The sand should be as fine as possible and clean to avoid further contamination. If you collect sand outdoors, rinse it first to remove visible impurities.
Top with gravel
Finish your filter with a thick layer of gravel. This final layer filters larger particles from the raw water and protects the lower layers from getting saturated too quickly. The gravel should be varied in size, from small pebbles to slightly larger stones for optimal filtration.
How to use your homemade water filter
Pour the water to be purified into the top of the filter (gravel side). Let the water pass naturally through the different layers and collect it at the neck opening. If the water flows slowly, it usually indicates that your filter is working correctly.
Understand that this DIY filter does not guarantee completely safe drinking water. It mainly removes solid particles and some chemical impurities but does not eliminate potentially dangerous bacteria or viruses. We recommend using a Weeplow gravity water filter.
- It has a two-year lifespan.
- It is portable and easy to use without electricity.
- It removes 99.99% of contaminants such as viruses, bacteria, and PFAS.
After this primary filtration, always boil the collected water for at least one minute to eliminate pathogenic microorganisms. At higher altitudes, increase boiling time slightly, as water boils at a lower temperature. Finally, use the gravity water filter to ensure your water is fully safe to drink.
How to replace the materials?
If you are in the wilderness, you may not find all the materials, even if the planet is highly polluted. A bandana can be replaced by a t-shirt or plant moss. Natural charcoal can be obtained directly from charred campfire wood.
Survival expert Jacob Karhu suggests an interesting natural variant. Use a bandana for the first layer, then add fresh plant moss, sand, and natural charcoal. This natural filter is very effective in the wilderness as the materials are easy to find.
To obtain water safe for consumption, eliminate the last biological contaminants by boiling, chemical treatments, and the Weeplow gravity water filter. The latter replaces all other purification methods.
What is the lifespan of your DIY filter?
Your improvised water filter can be reused multiple times but requires regular maintenance. Change or clean the cotton or fabric after each heavy use to prevent mold or bacteria. Also replace activated or natural charcoal every three to four uses for better filtration.
Sand and gravel can be rinsed and reused multiple times as long as they remain clean and free of visible contamination. This is a DIY solution, and there is still a risk of illness from contaminated water. That’s why we recommend using a gravity water filter that can last 2 years.
This activity can be fun and educational—you could even make a water filter with your children. However, in survival situations or crises related to water access, more reliable methods should be considered. Your DIY filter will help in unexpected and dangerous outdoor situations when you don’t have your usual equipment.
