How to Make a Charcoal Filter for Water: Here’s How

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Making a charcoal filter for water is one of the most useful skills you can learn as a survivalist. Along with removing the need to carry water-purifying chemicals all the time, charcoal filters can help increase your intake of essential minerals.

Below you’ll find a guide on how to build a do-it-yourself charcoal filter to clean dirty water. Keep reading for a step-by-step tutorial on making a charcoal filter for water and how to make found water safe to drink.

How to Make a Charcoal Water Filter for Water

When it comes to making a charcoal filter to clean water, the process can be broken into a few simple steps. Below you’ll find a breakdown of the method you should follow for building a charcoal water filter from scratch.

Choose a Filter Vessel for the Charcoal Water Filter

The vessel for creating a charcoal water filter needs to have a funnel shape, with a wide-mouthed opening at the top and a narrowed opening at the bottom.

Filter vessels for charcoal water filters should ideally be made of transparent material so you can see the outcome of the filtration process. The filter vessel material also needs to hold water without leaking. Good options are clear plastic or glass.

Here are some materials you can use to make a charcoal water filter vessel:

  • Plastic bottle: Large plastic soda bottles with the bottom of the bottle sawed off make ideal filter vessels since they have a narrow spout at the mouth of the bottle that can serve as a funnel. Making charcoal filters is also a good way to reuse old plastic bottles.
  • Glass: Glass bottles like old wine bottles can also be used as filter vessels for charcoal water filters if the ends of the bottles are cut off and ground down to prevent glass from contaminating the water. However, the downside of using glass is that it can be fragile compared to plastic water filters and cutting glass is more difficult than cutting plastic.

Any material container that holds water and can be formed into a funnel shape can theoretically be used as a charcoal filter for water. Plastic bottles are arguably the best choice since they can be easily replaced, they’re translucent, and they’re easy to shape into a funnel.

Add Pre-Filter Materials to the Charcoal Water Filter

Before the charcoal is added to a charcoal water filter, you need to add the pre-filter materials. While charcoal is effective at removing organic compounds and carbon-based contaminants from the water you’re trying to purify, pre-filter materials are added to help remove the sediment that is suspended in the water. This is what makes water look muddy or dirty.

Pre-filter materials are layered in the charcoal water filter nearest to the funnel opening, starting from largest material pieces to smallest. This layering method helps prevent the smaller particles of filter material from being washed through during the filtration process. Here are some examples of pre-filter materials used in charcoal water filters:

  • Small pebbles or gravel
  • Large, coarse sand particles
  • Fine sand particles
  • Coffee filter material

While pre-filter materials are not effective at removing bacterial or chemical contaminants, they are effective at removing sediment and making water more appealing to drink. Pre-filter materials also help to weed out some larger biological agents like mosquito larvae and other water borne insects.

Add Charcoal to the Water Filter

The active ingredient in charcoal water filters is the charcoal itself. It’s important to know the use of charcoal in charcoal water filters to understand which types of charcoal are safe for filtration and what contaminants charcoal is effective against in a water filter.

What Type of Charcoal Is Used for Water Filters?

The type of charcoal needed to make homemade water filters is activated charcoal. Charcoal is “activated” when it is combined with an activating agent or a gas to increase its surface area. This makes it more effective than unadulterated charcoal at scrubbing contaminants from the atmosphere and water sources.

Activated charcoal is very different from the grilling charcoal that you have in your home. Grilling charcoal should not be used to make charcoal water filters because it is often treated with fire accelerants and other chemicals. Grilling charcoal also usually comes in hard briquettes that are difficult to break down for an effective water filtration layer.

How Effective Is Charcoal as a Water Filter?

Activated charcoal is a highly effective filter that can remove most volatile organic compounds from unpurified water. Here are the reasons activated charcoal is considered one of the most effective water filtration materials:

  • It doesn’t remove salts and minerals: One of the major disadvantages of chemical water purifiers is that they remove beneficial salts and minerals from drinking water. Over time, this can leave survivalists at risk of malnourishment. Activated charcoal not only doesn’t remove these minerals, it adds additional beneficial minerals to your drinking water.
  • It is easily operated and sourced. A charcoal water filter is so simple in design that a child could build it, making it one of the most accessible forms of survivalist equipment available. Activated charcoal is widely available in many stores and online in bulk. It also stores well long-term when it is properly sealed and secured.
  • It removes off tastes and odors. Even in an emergency situation where survivalists have no other choice, it can be off-putting to drink water that has a stagnant flavor or taste. Running pond or puddle water through an activated charcoal filter can leave it tasteless and odorless, making it much easier to drink.

In the long run, learning how to make and operate homemade charcoal water filters is a more feasible option than stocking up on water purifying tablets. While both options are good to have on hand in case of an emergency, charcoal water filters can be built even if you run out of chemical purifiers.

How Does Activated Charcoal Filter Water?

Activated charcoal filters water by binding chemically with any volatile chemicals present in the water. Activated charcoal is formed by treating charcoal with oxygen until it becomes extremely porous. This porous quality makes activated charcoal effective at absorbing toxins and pollutants in either oxygen or water.

Activated charcoal is especially good at purifying organic compounds. Since all organic compounds are carbon-based, they are naturally attracted to the carbon present in the activated charcoal. Once bound to the charcoal, these compounds become neutralized.

Can You Make Activated Charcoal from Briquettes?

Most charcoal briquettes are not suitable for making activated charcoal because they’ve been chemically treated. However, if you have organic charcoal briquettes, you can use a 25% calcium chloride solution to treat charcoal briquettes and turn them into activated charcoal. In general, it is easier to source activated charcoal in bulk than to make it yourself.

How Do You Store Activated Charcoal for Water Filtration?

If you’re trying to include activated charcoal in your prepping supplies, it’s important that the charcoal is stored properly to retain its effectiveness. Here are some tips for storing activated charcoal for water filtration:

  • Store it in a cool, dry place. Activated charcoal should be stored in a sealed container to prevent it from accumulating moisture, preferably in a temperature-controlled environment like an indoor pantry or bunker.
  • Store away from flammable objects. While activated charcoal is not as flammable as other forms of charcoal due to its tendency to draw moisture, it is still weakly explosive in a powdered form. Make sure that charcoal and other flammable materials are kept away from open flame or sources of heat, like radiators.

Is Activated Charcoal Expensive?

Commercially prepared activated charcoal is relatively expensive at around twelve to fifteen dollars a pound. This makes it a precious resource for survivalists. If you want to stock up on activated charcoal in bulk, it can be worth it to make the charcoal yourself, as this drops its cost to around a dollar or two per pound.

Whether you make your own or stock up on commercially prepared activated charcoal over time, it’s worth the investment to stockpile this resource for emergencies. Along with water filtration, it can also be used to treat overdoses, poisonings, and viral infections.

Add Water to the Charcoal Filter

After you layer pre-filter material and a layer of activated charcoal in your charcoal water filter, you’re ready to add the water that needs to be filtered.

Add a catch container at the bottom of the water filtration system to catch the purified water. Once the catch container is in place, pour water gently into the opening at the top of the water filter to minimize disruption of the filtration layers in the filter.

As water slowly seeps through the charcoal water filter, it should begin to seep purified water from the funnel opening underneath.

Depending on how much pre-filter material you have in your charcoal water filter, it may take several minutes for the water to completely seep through the filter. It’s a good idea to build a stand for the water filtration system over the catch container so you don’t have to stand there and physically hold the filter over the catch while it’s filtering the water.

Will Charcoal Filters Kill Pathogens?

While activated charcoal water filters are effective at removing chemical pollutants and sediment from drinking water, the one thing that charcoal filters will not filter out of water is microbes and bacteria. Activated charcoal has no adverse effect against most of these pathogens, so they will still be present in drinking water until it is sanitized.

Once water has been cleaned through charcoal filtration, there are several methods you can use to remove bacteria and pathogens:

  • Boil the water: If you have access to fire-making supplies, boiling water before drinking and after filtering through a charcoal filter is the safest way to drink sourced water that isn’t from a clean source.
  • Water purification tablets: Water purification tablets can be used to sanitize water as well as clean it of toxins and impurities. Once water has been treated with water purification tablets, it should be safe to drink.
  • Bleach: Small amounts of bleach in water can be used to clean the water of pathogens in an emergency situation. Use an eyedropper to add 6-8 drops of bleach per gallon of water according to the EPA. Be sure to measure out the bleach carefully, as excess bleach can be dangerous to drink.
  • 0.01 micron filter: After filtering water through a carbon filter, water can be further filtered through a fine 0.01 micron filter sieve to remove any remaining pathogens that remain. 0.01 micron filters are capable of filtering out bacteria-sized agents from water, leaving it completely pure.

After destroying any bacteria or microbes present in the purified water and running it through a charcoal filter, it should be safe to drink.

Can Charcoal Filters Remove Radiation From Water?

The question of whether activated charcoal can remove radiation from water is a complicated one. According to the U.S. Water Systems, carbon filtration can be somewhat effective at removing radioactivity from water sources, but only as part of a multi-filtration system that also includes reverse osmosis and ion-exchange water softening.

Unfortunately, this means that homemade charcoal water filters are not going to be that useful for the purification of water that has been contaminated in a nuclear event.

As a backup resource, survivalists should pack potable water in a radiation-safe place as well as have the materials in place to build charcoal filtration for other questionable water sources should their potable water run out.

Charcoal Water Filters Are Practical for Bushcraft

Even though charcoal water filters aren’t useful for filtering all materials out of water, they’re an effective resource in a pinch if you need to quickly clean a questionable water source of excess sediment and contaminants before boiling it.

While they might not filter out microscopic threats like radiation and pathogens, charcoal water filters are a useful way to make a natural water source much more appealing and safe to drink.