How To Build An Activated Charcoal Water Filter For survival

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Last Updated on April 9, 2023 by

Today we are going to talk about building water filters so that just in case you get stuck in a grid-down scenario, you will be confident that you will have clean drinking water.  

Keep in mind that the items that are needed to build this charcoal water filter will need to be gathered before the ball drops.  Meaning, this post is written from a prepping point of view.  Learn how to make this before the SHTF and you will feel confident you’ll have clean drinking water for you and your family at any time. 

There is a lot of curiosity and questions behind using and building a charcoal water filter, so I wanted to try and get some of those questions answered today and also show you a little experiment on just how easy it is to build a DIY charcoal water filter.

So let’s begin!

What Is Activated Charcoal?

The first thing to know about using charcoal to filter water is that it isn’t the same as the charcoal bricks that you use to barbecue.  When filtering water for drinking, you will use what’s called activated charcoal, which is usually pressed into a solid block or sold as loose beads.  

You will also hear activated charcoal referred to as activated carbon. They are both the same thing, and can be used interchangeably.

How Is Activated Carbon Made?

The charcoal is heated to over 1700 degrees Fahrenheit then treated with a nitrogen and argon to create a very porous structure, which ends up creating a highly effective material for filtering water.  

It’s a little more complicated than that, but you can read more about how to make activated charcoal here.

How Does Activated Charcoal Work?

Activated charcoal works using adsorption as opposed to absorption.  Essentially you are removing impurities from the water chemically rather than physically.  Because the impurities are bonded to the charcoal, once the pores are filled up, you need to replace the activated charcoal filter.  

But for emergency situations, you will be using the specific method described below so you won’t have to worry about changing filters necessarily.

How To Build A DIY Charcoal Filter

how to make a charcoal home filter

Supplies Needed For A Small DIY Charcoal Sand Filter​

Before we get started on how to make a DIY charcoal and sand filter, I want to state a few things for the record.  The below instructions are based around providing enough drinking water for yourself and assuming you have some time on your hands if you’re caught out in the wilderness.  

You will notice that the instructions call for 12 oz. water bottles and a 32 oz. Gatorade bottle.

If you want to build a larger charcoal filter for you and your family, I would suggest building it out of 5-gallon buckets.  It’s a similar process, using pretty much the same exact filtration media, you are simply buying it in larger quantities.  

Below are the items you will need to build your primitive charcoal and sand filter. You can also use a 2 liter soda bottle as well.  I used smaller containers for experimental purposes only: 

homemade charcoal water filter
  • 12 oz. Water Bottle with cap on (1)
  • 32 oz. Gatorade Bottle (1)
  • Fine-grade activated charcoal or coconut shell activated charcoal (charcoal made from coconut shell is supposed to be better than activated charcoal made from wood – take your pick!)  If you don’t have activated charcoal, you can still build a filter out of regular charcoal from a prior wood fire.  You will need to crush the charcoal as fine as you can with a rock so that it can clean the water properly.
  • Sand.  You are going to want to clean the sand first if you can with water.  Find some sand near a creek bed or near a lake if possible. 
  • Cotton ball or coffee filter(1) – Cotton balls are something you should be carrying with you in your EDC kit or your bug out bag anyways.  You’ll need one for your water filter. This will be the last barrier before the clean water is collected into the Gatorade bottle. You can also use a coffee filter and tie it off on the outside with the rubber band to act as the final barrier. 
  • Granular small stone – think about fish rocks in a fish tank.  That size would work well. Or if you’re near a creek, you should easily be able to gather some at that point. 

How To Make A Charcoal Sand Water Filter​

Step 1:   Collect the dirty water that you are going to filter and set aside.  If you can set aside for a 1-2 hours, it will allow anything that floats to rise to the top and then you can easily skim off some debris right from the start.

Step 2: Water bottle. Cut off the bottom of the bottom of the water bottle.  This is the bottle that will become your charcoal and sand filter.

Step 3: Water bottle cap: With the cap still on the water bottle, take your knife and twist a small hole in the cap about an inch in diameter. 

Step 4: Cotton: Take your cotton ball and push it tightly against the cap. This will be the final barrier before the water comes out clean. 

Step 5: Gatorade bottle.  The Gatorade bottle will collect the clean, filtered water once completed.   

Step 6:  Activated Charcoal: Next, take your activated charcoal and pour a small amount (about 2-3 inches) on top of your cotton ball.  If the water runs rather than drips through the filter, you will need to pack your charcoal tighter.

Step 7:  Sand: Once you’ve placed the activated charcoal on top of the cotton ball, then place a layer of sand on the top about 4 inches thick.   The sand will be a majority of your filter. 

Step 8: Granular smaller rocks.  You will now place a thin layer of these granular small rocks on top of your sand.  Again, this is just another layer to get the bigger particulates out of the water first.  You can add another layer of larger rocks on top if you want.  It just depends on what you are trying to filter out. 

how to you make a charcoal water filter

Make sure that you boil your water after you have filtered it if you can. You need to get rid of the other microorganisms in the water that are still present.  This can be accomplished using a Jetboil or building a fire, of course.  

Alternatively, if you’re on the move and can’t stop to build a fire,  you can put some iodine tablets in your freshly filtered water, which will complete the water purification/filtration process.

Other Things To Consider When Building Your Charcoal And Sand Filter​

Since I always want to talk about practicalities in a real-life survival situation, even something as simple as a water bottle might not be available to you.  

Due to that, if you’re out in the wilderness a few other options are available to you, such as a sheet of tree bark rolled into a cone or a clay pot with a small hole in the bottom. Essentially anything that you can use to create a water bottle-like structure. 

This can also include a piece of cloth large enough in which sand, gravel, and charcoal mixture can be added to it.

Also take note, if you’ve done any research on how to make a charcoal water filter, there are several different opinions and variations.  Don’t worry about that.  

My suggestion would be to try different layering techniques and find out which ones cleans the best.  That’s what I had to do.   You can also try using different quantities of each filtration media to determine which combination works the best. 

Another recommendation is to test the water in your area before a grid-down scenario happens.  This way you will know what contaminants you need to be filtering for.  

To learn about USGS monitoring activities in your state, call or e-mail the U.S. Geological Survey (USGS) representative. A list of contacts is at http://water.usgs.gov/district_chief.html.

Final Thoughts

I hope you’ve learned the difference between purification and filtration of water by reading this post.  If you didn’t get a chance to read What Is the Best Way To Purify Water: Part 1, make sure to read it as an important supplement to this post.  

There are a few other ways to filter water that weren’t mentioned here.  Feel free to view to check out other ways to successfully purify water when you’re away from home

Always remember that if you are in an area where you are unsure of the water, filter it first to remove the big stuff, and then when in doubt, boil it.  Boiling is known to be the safest, most effective way of removing all microorganisms from the water so that it is safe to drink in any survival or emergency situation.