How To Build An Activated Charcoal Water Filter For Survival

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In a survival situation, the most important resource that you are going to need after food is water. Whether it be a flood or the zombie apocalypse I’m sure everyone can understand why that is. Now, storing water can work but it’s expensive and there is a limit to how much and how long you can store. So, building a filter such as an activated charcoal water filter might be a more intellectual decision. 

You can make a charcoal water filter by stacking layers of gravels or rocks, coarse or fine sand particles, and activated charcoal in big or small containers. The water that is filtered by this setting will filter out any impurity in the water and make it clean enough to drink.  

But this is just an oversimplified instruction to the actual process. So, please read till the end to figure out how to how to make an activated charcoal water filter, how it works, and much more on the topic of water purification. 

Steps of Making an Activated Charcoal Water Filter 

You can easily make a water filter using activated charcoal, in any part of the world with the things available within your arm’s reach. The basic structure consists of – a layer of gravel, a layer of rocks, a layer of sand, and the final layer of activated charcoal. Water flows down all these layers to collect at the bottom which is then available for your daily usage.

The materials required do not cost much and are very easily accessible. Take a brief look at the following steps:

Step 1: Make or buy activated charcoal

Activated charcoal is a modified version of regular charcoal. When pure Carbon particles are heated over and over, they convert to activated charcoal. This is basically the wood dust or coal-like particles obtained after burning wood in high temperatures. It looks greyish in color and may appear as big chunks. Regular charcoal is inert and doesn’t react with substances easily.

To make this charcoal activated,

  • First, powder your big chunks of charcoal.
  • Prepare a 25% Calcium Chloride solution. You have to mix three parts water and one-part Calcium Chloride in a container, to prepare this solution.
  • Add your charcoal powder to the Calcium chloride paste. 
  • Spread the entire mixture on a tray and let it dry for a day. Some prefer drying it under bright sunlight. 
  • Then bake it in the oven at 230 degrees. There you have your activated charcoal!

The most special and unique criteria of this activated charcoal is that it is highly porous and has a huge surface area. Making your own activated charcoal is quite tiresome. But it is so easily available and so cheap that you can just buy some instead of making it.

A bag of activated charcoal may cost you about 7-8 dollars and can be easily found in your nearest pet shop or Walmart store. If you live in a disaster-prone area, keep a bag of activated charcoal in your house as your backup!

Step 2: Determining the size of your filter

Select the dimensions of your filter. It will depend on the duration of usage, number of consumers, location, and usage purposes. 

If you are going camping, a filter about the size of a water bottle is the best. It is easy to carry and can provide you with clean water in no time. But if it is to feed one or more families such as during flood or drought, build a large one with buckets or tanks.

Step 3: Select your containers

As per your needs, select your containers. For a small-scale filter, take two water bottles – one large and one a bit smaller. Cut both bottles at their ends. Make a hole for the tap at the bottom of the larger bottle.

For a large-scale filter, you may use water buckets or old oil tanks or you can buy new ones. You will need 4 of them. Check if they are leak-proof. Now, carefully remove the bottom of the top three buckets. Keep the intact bucket at the lowest level and stack the other three on top of it. Make a hole for the tap at the lowest bucket.

Step 4: Use a net or mesh between layers  

To filter the water through the layers, you need nets. You can use mesh or window screens or coffee filters as per the size of your containers. 

In small filters, you can put cotton or cheesecloth at the neck of the smaller bottle. Use a coffee filter or any net cut according to the size of the bottle cap. Then attach it to the open end of the bottle. Keep the smaller bottle upside down on top of the larger bottle.

In large filters, use meshes with different pore sizes. For the sand and activated charcoal layer, use the mesh with the smallest pores and for the gravel or rock layer, you may use a mesh with comparatively bigger pores. Now, attach the meshes at the bottom of the top three buckets. For four bucket filters, you will need three meshes. 

Step 5: Collect materials and start stacking the layers

Once you have created the infrastructure, now assemble your materials. You need pea gravels, rocks, fine or coarse sand particles as per your need, and activated charcoal in generous amounts. Wash the sand first, about three to four times.

In small filters, put activated charcoal in the small bottle first, just above the cotton. Above this put fine sand. Now let the water flow once or twice through this setting. Do not drink this water yet.

Next, put a layer of coarse sand. Then add your gravels and rocks. At the top of all these places a sieve. Your filter is complete now. Pour boiled water through this setting twice and discard this water. Then wait for ten minutes. After ten minutes, your filter is ready to use!

In large filters, fill the third bucket with activated charcoal. Put a layer of fine or coarse sand on top of it. It is better to use fine sand. In the same way, pour water on it and discard it. This is just to clean all the dirt and impurities. 

Then put gravel on the second bucket and rocks on the first bucket. Cover with a lid. You may use a net or sieve at the topmost layer. Similarly, let boiled water flow through all these layers 2 to 3 times. Discard the impure water. After about an hour, your filter is fit for use. It is advisable to use boiled water always before you drink. Your filter is ready! Take a glass of water and drink to your heart’s content!

Following these steps, now you will easily be able to make your very own activated charcoal water filter whether on a small scale or a large scale.  

How Does an Activated Charcoal Filter Work?

A lot of people have this misconception that using sand, gravels, rocks, or charcoal in the filter contaminates water. But this isn’t true. Water purified by an activated charcoal filter is no less than that purified by bleach or chlorine tablets or even alum, in terms of safety.

Let’s try to understand the basic mechanism of this filter. The activated charcoal molecules are highly porous structures. This special feature enables them to absorb a lot of materials in the pores. Adsorbing means holding materials on the surface. So, the activated charcoal molecules can absorb lots of impurities on their surfaces. 

Naturally, a question comes to your mind, how does it adsorb the impurities then? The weak chemical bonds like Van der Waals forces existing between the chemicals help in adsorption. This bond holds the impurities tightly and can release them under pressure too.

It is said that about 1 gram of activated charcoal has a surface area of about 500-1500 square metres. So, imagine how much impurities only a gram can hold! 

Can Activated Charcoal Filters Remove Microbes Like Viruses? 

Since activated charcoal or activated carbon adsorbs minute particles on its surface, luckily enough it can adsorb a number of viruses too. Our drinking water is contaminated with bacteria, pests, pesticides, chemicals, toxins, viruses, and what not! The main purpose of a water filter is to provide safe and clean water that is free of all these.

Studies have confirmed, activated charcoal is capable of removing all the bacteria, molds, pathogens, bad odors, sediments, etc. from water and also some specific viruses. Namely, hepatitis viruses of the families – Flaviviruses, Hepadna, Picornaviruses, Delta viruses; Polio, etc. The presence of E. coli in water indicates sewage contamination. Activated carbon actively kills E. coli.

As you can see activated carbon can neutralize most common viruses and bacteria that transmit to humans through water and cause deadly diseases. So, I’m sure the germaphobes out there can rest easy knowing that their activated charcoal water filter is good enough to produce clean and safe water for drinking.  

Maintenance of An Activated Charcoal Water Filter 

The charcoal filters are very low maintenance filters and simple to use. During catastrophes, life comes to a standstill. Resources are so limited that you have to spend every single penny wisely. This charcoal filter is worth all your money and doesn’t require much maintenance. So, it is fit for survival. The components used are not perishable and can be replaced when required. 

In other filters where chlorine tablets and bleach are used, they require changing the water every once in a while, and much more troubles. But for a charcoal filter, once you set the charcoal you may change it after 2 to 3 years. Also, if you keep it covered and free from dirt, the pebbles, gravels, rock, and sand remain clean as well and do not require cleaning so frequently. 

Besides, changing the materials is no rocket science. You can easily collect all the materials again and replace them. Your filter becomes fit to use again! Replacing can be done once in 2 – 3 years. But it is wise to clean your filter once every 3 months.

Some people fail to differentiate between activated charcoal and regular charcoal. The easiest way to differentiate is to add one teaspoonful of the charcoal in question to a glass of water. If it produces air bubbles after mixing, this is activated charcoal. Regular charcoal does not produce bubbling or frothing.

These filters are so easy to set up, there is no need for electricity or to create an energy gradient, nor to keep a constant power supply. All the work of physics is done by the force of gravity and the chemical bonds inside the filter do the work of water purification. Gravity pulls the water downward and the clean water flow is thus maintained.

Considerations While Making an Activated Charcoal Water Filter 

Activated charcoal filters are simple to make and maintain. In remote areas, especially in the forests or villages, it is almost impossible to gain access to pure drinking water during disasters. Even if you are in the wild, you can certainly find the materials required to make an activated charcoal water filter.

Survival filters are supposed to be easily portable, simple to use, and cost-effective. Activated charcoal filters are the best choice among survival filters. A small-scale survival filter can roughly cost you about 5 to 6 dollars. But some common mistakes in making the filter can cost you a great deal. Some are mentioned here:

  • The charcoal should be fine and granular. Using big chunks may reduce the efficiency of filtration.
  • Don’t use one or two layers. Use as many layers as possible. The more, the merrier. Multiple layers help to filter water at multiple levels ensuring more safety. 
  • Don’t use dirty water. Always try to use boiled, comparatively clean, and cooled water.
  • Discard the first filtered water. This water is toxic to your health.
  • Don’t use glass pitchers. They break easily and are hard to clean.
  • Avoid using steel or iron made equipment which rust easily. Use materials that can be used for long and replaced with less cost.
  • Some people tend to make their own activated charcoal. This only consumes more time and money. You can buy a generous amount of activated charcoal with only a few bucks. These are more efficient and well designed to serve your purposes. 
  • Clean the sand as many times as you can, until the discarded water appears clean. Dry it in the sun and then use it in your filter.
  • Do not keep your filter open. Always cover it with a lid. Otherwise, the entire purpose of your filter will get destroyed. 
  • If the filtered water is not clean or transparent, never drink it. It indicates that the materials are not ready to use yet. Keep filtering until the water is clean.
  • Avoid keeping the filter in hot areas. Keep it in a cool and humid place.
  • Avoid using water from known toxic sources. If a water source, e.g., a well or a pond has been reported to contain alarming amounts of toxic substances like arsenic, lead or other heavy metals, avoid using water from that source. Water should always be obtained from a known healthy source.
  • Avoid using very hard water. 
  • Maintain the standard pH of water. Water with a pH of 7 or slightly above is similar to the pH of body fluids and helps to fight infections. 
  • If you are filtering river water or pond water or even rainwater, boil it first. Boiling at 100 degrees kills all the bacteria and viruses. Boiling beforehand always ensures additional safety. 

What Are the WHO Standards for Drinkable Water? 

The World Health Organization has devised some criteria or standards that define safe water. The water filtered by activated charcoal is capable of meeting these standards largely. Though the filter is made out of scratch, the filtered water is very pure and fulfills all the parameters of safe water, which is your dire need during survival. Some basic standards are mentioned below. 

  • Should be free from all pathogenic agents, e.g. Escherichia coli.
  • Should be free from harmful chemical substances, e.g. heavy metals like Arsenic (As), Lead (Pb), Mercury (Hg), Cadmium (Cd), etc. 
  • Should be free from colors and bad odors.
  • Should come from a known safe source. 
  • Pleasant to taste. 
  • Usable for domestic purposes. 
  • Easily available. 

Reference:  WHO Guidelines for Drinking-water Quality


Activated charcoal water filters are gaining more popularity as survival filters. Be it large scale or small scale, you can easily make it with the materials available around you. By now you have learned how to make an activated charcoal water filter, the advantages of using activated charcoal in your survival filters, and all the important stuff related to it.

Thank you for holding your breath and reading this entire article. I hope this article helped you prepare for survival situations. Good luck with building your activated charcoal filter and ensuring a safe water supply! Have a great day. 


Shanna is the 2nd half of Top Outdoor Survival. Like Forest, she has a passion for guns and knives. They love to go on a survival trip at least once a year. They love to go camping, hiking, and traveling.

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