How to Make a Charcoal Water Filter (2024)

Key Takeaways

Making your own activated carbon filter for use during an emergency scenario is easy and inexpensive.

With just a 2-liter bottle, some granular activated carbon from a fish supply store, and a bundle of pure polyester fiber, you can be drinking clean water in minutes.

Keep these items and this how-to guide on hand in your bug-out bag or emergency stash.

What Is Activated Carbon Filtration?

Activated carbon is made by a very specific heating process that gives materials that contain carbon certain properties that make it adsorb molecules, i.e., contaminants and impurities, from water.

Such materials include coal, coconut shells, wood, even peach pits.

After heating, activated carbon has an immense surface area with countless microscopic pores and cavities, and that’s where the adsorption takes place. A chemical attraction attracts impurities into these pores and channels, trapping them.

When water passes over and through the carbon, impurities in the water are attracted to the carbon’s surface and get trapped, leaving the water cleaner as it exits the water filter.

If you’re interested in purchasing an activated carbon filter for your home, skip the science experiment and check out my reviews of the best whole-house carbon filters.

How to Make an Activated Carbon Water Filter

You may think, based on inaccurate information on the web, that this process involves charcoal. It doesn’t. Especially not grilling charcoal or anything like it.

Activated carbon can come from coal materials, but it is not charcoal. The main ingredient for making your own activated carbon filter is, you guess it — activated carbon.

Filter materials

Granular activated carbon (GAC): widely available, sold for fish tanks
Plastic bottle or similar container: 2-liter soda bottle will do, clean it first
100% polyester fiber with no flame retardant: widely available

Step-by-step guide

Step 1: Cut the bottle. Flipping the 2-liter bottle upside down, cut off the top 1/4 (this would be the bottom if it were right-side-up).

Step 2: Add fiber. Stuff a handful of polyester fiber into the bottom 1/4 of your bottle filter (this would be the top if it were right-side-up).

Step 3: Add carbon. Add your activated carbon on top of the polyester fiber — the more, the better — but leave space at the top for more polyester fiber.

Step 4: Add more fiber. Place another handful of polyester fiber on top of the carbon. The result is a sort of activated carbon sandwich.

The reason you add fiber on either end of the carbon is to slow down the rate at which the water flows through the carbon. When the flow rate is slow, the water has a longer contact time with the carbon, and the carbon is able to adsorb more impurities.

Step 5: Rinse. Pour water through the top of your homemade filter cartridge to flush the activated carbon and get rid of air bubbles and rinse any (harmless) dust from the activated carbon.

Using the filter

A note about microbial contamination: While your homemade activated carbon filter will remove many impurities, it won’t kill bacteria and viruses. What you can do is boil the filtered water for at least 10 minutes to ensure it’s safe to drink, then allow it to cool and send it through your carbon filter.

When it comes to how you actually use this filter you’ve made, you have a couple of options.

Buy a stand for it: Believe it or not, you can actually get a stand for this exact type of filter, complete with a little faucet. Check out this one on Amazon.
Drill a hole in the cap: You can drill a 1/4-inch hole in the cap so the water will trickle out slowly into whatever receptable you’re adding it to, whether it’s a glass or a barrel.

If you’re in a scenario where you don’t have access to clean water for whatever reason, but you do have access to these materials, it’s a good idea to refresh the filter with new materials about once a week, and simply toss out the old stuff.

This is a small filter for temporary use, and it will fill up with contaminants rather quickly. It’s not a long-term solution.

How to Make Activated Carbon at Home

You can’t.

Making activated carbon is a complex process that involves heating carbon materials to temperatures that you cannot achieve at home.

Luckily, activated carbon is affordable and readily available.

The Marvels and Limits of Activated Carbon in Homemade Water Filtration

Your homemade activated carbon filter will be a good friend to you during your emergency situation, but it will only get you so far.

Adsorption power

Activated carbon’s primary strength lies in its ability to adsorb a vast array of contaminants, even the homemade GAC version. But what exactly can it trap?

Volatile organic compounds (VOCs), such as pesticides and herbicides
Natural organic materials, such as tannins
Chlorine, chloramine, and chlorine by-products
Some heavy metals, such as lead, mercury, copper, etc.

Limitations

Keep in mind, this homemade activated carbon filter is for emergency scenarios, and it has limited application. For example, it’s unlikely to remove bacteria. For that, you need activated carbon block, or even a more complicated filter, such as a UV purifier. (See my note about boiling above.)

Here’s a list of the best UV purifiers.

Bacteria and viruses: Viruses and bacteria are too small to be trapped by activated carbon granules.
Hard minerals: Minerals that cause water hardness, like calcium and magnesium, aren’t effectively removed by activated carbon. If you’re looking to soften your water, you’ll need a dedicated water softener.
Saltwater desalination: Unfortunately, activated carbon can’t remove salt from water. Desalination requires more advanced methods, like reverse osmosis, which unfortunately may not apply to emergency scenarios.

Conclusion

If you’re in an emergency scenario, or you’re expecting one, it’s useful to know how to make a water filter.

While this filter won’t remove every waterborne contaminant under the sun, if you combine this filter with boiling, you can drink safe water until the emergency passes.

Crafting a DIY filter is not only possible, but it might be fun too.

Interested in knowing more about water filters? Explore their importance in maintaining a reliable water supply with these additional resources:

FAQ

Can you make your own carbon water filter?

Yes, you can craft your own carbon-based water filter using basic materials, including a soda bottle, polyester fiber, and activated carbon.

How do you make a homemade carbon filter?

Start with a 2-liter soda bottle, cut off the bottom, flip it over, and add a layer of polyester, followed by granular activated carbon, and then another layer of polyester fiber.

What kind of carbon do you use to filter water?

Water filtration uses activated carbon, which can be made from a number of carbon-based materials, usually coconut shells or wood, placed under extreme heat to activate the adsorption properties of carbon.

Can you use wood carbon to filter water?

Yes, activated carbon made from wood can be used for basic filtration, but ensure it’s natural and free from any additives or treatments.

How to Make an Activated Carbon Water Filter (2024)