Water Purification: Improvised Charcoal Filter

(As featured in the May/June 2010 issue of Practically Seeking)

Charcoal Water Filter

"Water water every where and not a drop to drink."
In a survival situation water IS life, and yet so very much of it is potentially contaminated. It is ALWAYS best to assume the ground water is not safe to drink straight from the source, and to take the appropriate actions to purify any water you obtain. The ONLY way to be absolutely sure all potential pathogens in your water have been neutralized is to boil it.

However, the use of an improvised charcoal filter is a great way to remove sediments, remove many potentially harmful contaminants, and to improve taste.

Charcoal is used in many household and back-country water filters, and in my experience with primitive filtration methods, it is also the easiest and most effective method to use in the field.

We are using a 2-liter plastic bottle for the "see through" value, but many other options are available to you, such as a sheet of tree bark rolled into a cone, a clay pot with a small hole in the bottom, a length of bamboo or cane, a glass bottle with the bottom removed (see our YouTube video)…  Besides, these days, sadly, there is almost always plenty of usable refuse out there on the landscape :(


Step-by-step Instructions on How to make an Improvised Charcoal Water Filter:

  1. Obtain FRESH charcoal that has cooled completely. To create a good supply of charcoal, create a camp fire and when you have a good coal bed, bank your fire by covering it with dirt or ash and come back in a day or two. Uncover the charcoal and allow to cool completely before removing. 
  2. Make Charcoal Allow to cool

  3. Crush your charcoal into small bits, from powder up to the size of aquarium gravel.
  4. Charcoal and pounding rock Crushing charcoal Small bits

  5. Obtain or fashion a cylindrical container (taller is better than wider) with open ends. Julie is using a 2-liter soda bottle with the end cut off.
  6. Fashion an open-ended cylinder Soda bottle with end cut off

  7. Fill the smaller opening with tightly-packed grass or a piece of fabric (if both ends are the same diameter choose either one) to prevent the charcoal from falling out or running through with the water. Or if you are using a bottle that still has it's cap, as we are, poke a small hole in the cap before placing your fabric/grass.
  8. Make small hole in cap Pack smaller end with cloth or grass Pack end tightly

  9. Pack the crushed charcoal into the container TIGHTLY.  The idea here is to create as fine a matrix as possible for the water to DRIP through slowly, thus trapping more sediment and "wee beasties". If the water runs rather than drips through the filter, you will need to pack your charcoal tighter. You should have enough crushed charcoal to fill your cylinder up about halfway.
  10. Charcoal into cylinder Pack the charcoal tightly Fill cylinder halfway

  11. It is a good idea to place a couple of inches of packed-down grass or sand, or another piece of cloth on top of the charcoal to prevent it from becoming displaced when you add your water.
  12. Top charcoal with sand Pack sand firmly

  13. Place your filter atop a container to catch your water. We are using a glass jar so you can see the changes easily, but in a wilderness situation it is a good idea to filter directly into the pot you are going to boil the water in rather than the one you will be drinking from (in the event they are not one in the same).
  14. Place filter on top of catch container

  15. Slowly pour the untreated water into your filter (being careful not to displace your sand) filling the remainder of your cylinder with water and allowing it to slowly percolate through. Remember, the water should DRIP SLOWLY out the bottom of your filter.
  16. Water to be filtered Pour water slowly Wait for water to percolate through Drip Slowly

  17. After all of the water has run through the filter, pour it back through as many times as needed to make it clear. I usually run it through at least two, preferably three, times.
  18. Once through the filter Pour through 2 or 3 times Third pass through filter

  19. Once the desired clarity has been achieved, bring water to a boil for a few minutes in order to make sure it is completely sterilized. Remember, boiling is the only way to ensure safety from pathogens. (Taste can be further improved by adding a small lump of charcoal to the boiling water.) Enjoy your clean water!
  20. Bring water to a boil Safe, Clear Water!


Remember, you stake your life on your water source and
contaminated water can cause debilitating effects that can prove fatal in a survival situation!
Never take chances and always use the absolute best filtration methods
available to you under the circumstances.

Until next time, Be Well and Have Fun!