Charcoal specific to filtration purposes is called Air, Water, or Vapor phase carbon. They are manufactured in a precise manner to achieve the desired application.
Charcoal made for water purification is ‘activated’.
But in a pinch, you can use BBQ lump charcoal (not briquettes as they may have binders and chemicals). And here is how you can do it.
How to make an Improvised Charcoal Water Filter:
- Use charcoal from a reputable source
- Crush your charcoal into small bits, from powder up to the size of aquarium gravel.
- Use a tall cylindrical container (taller is better than wider) and punch some small holes at the bottom.
You can pour water at the top, and the purified water will come out the bottom. Don’t make the holes too big, you want the water to spend as much time as possible with the charcoal to filter the water.