This article is the second article in a two part series on water purification originally posted on December 11, 2019. The author, Lisa Vargas has her own site called I need to and is worth your time to visit and comment if you are so inclined. She is also working her way through the Amateur Radio Technicians text book with hopes of obtaining her Technician Ticket by the end of March. Enjoy! – JohnyMac

In this post, we will focus on ways to filter water as opposed to ways of purifying water.  As you learned in Water Purification in a Grid Down Situation – Part 1 the first article of this series, I posted; purifying water and filtering water are two different things.

If you are stuck in a situation where you don’t have clean water readily available, it is vital to know these various ways to either purify, or at least filter the water so you don’t get extremely sick, or worse.

Filtering water is similar to purifying water except that we are using physical barriers to get rid of dirt and grime in the water as well as bacteria and other microorganisms.

Remember, filtering water will not get rid of as many microorganisms as purifying water, so if you can, always boil the water after you have filtered it for extra protection.

In a survival situation, I’m always a big proponent of talking about the items that we can carry with us. High-quality water filters from a store will ensure that no harmful pathogens or microorganisms are getting into your drinking water.

But sometimes using store-bought, high-quality water filters might not be an option, unless you remembered to include a water filter in your bug out bag.

Meaning, if we are in a grid-down situation, you need to be able to utilize the things you have with you, or you need to be able to find items out in the open that you can use to pre-filter your water.

Filtering Water With A Cloth

Using various types of cloth to pre-filter water is going to be your best bet in any survival situation.   You can use socks, t-shirts, or anything that is cotton and tightly woven together.

You simply will pass the water through the cloth into another container in order to filter it.  This will remove many of the particulates and debris that you don’t want to drink.

One device that makes filtration super easy is the Millbank bag.  You can get one at Millbank Bags USA. They have a fantastic video below that shows step-by-step exactly how to use the Millbank bag to filter water.

It’s very simple and easy to use and is a perfect backup just in case something happens with your main water filtration method. 

But just in case you don’t have a Millbank bag or something similar, I learned a great trick from an ex-military helicopter pilot that works wonders.  He showed me how to take a pair of old jeans, run one pan leg through the other, then use a zip tie to close off the bottom.

In this way, the old pair of jeans acts like a makeshift Millbank bag.  You can also use a primitive version of the Millbank bag which essentially is a cloth bag used to make nut milks.

You can add layers of sand and activated charcoal (if you have some in your bug out bag) in the sack to help filter the water.  You can learn more about making a homemade charcoal and sand filter here.

Once you’ve filtered your water, don’t forget to boil it if you can to make sure the water is 100% safe to drink.

How To Use Charcoal To Filter Water

The first thing to know about using charcoal to filter water is that it isn’t the same as the charcoal briquettes that you use to barbecue.  At the same time, if you are in a survival situation, a charcoal briquette may be all that you have, assuming you’ve prepped and have one with you in your bug out bag.

Another option if don’t have activated charcoal, you can use finely crushed charcoal from a freshly burned campfire, but ideally, to get your water as clean as possible, activated charcoal is your best solution.

Activated charcoal is a form of carbon that is processed to have small, low-volume pores that increase the surface area available for adsorption or chemical reactions.

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

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.

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.

There are a few variations for using activated charcoal to filter water, but most have the same basic principals.  For the purposes of this article, we are going to be assuming you are stuck in a compromising situation where no clean water is available to you and your family.

With that said, you can learn how to build your own charcoal filter fairly easily, so make sure to add that to your list of survival skills to learn if you haven’t tried it yet!

If you don’t have the materials to make a basic charcoal filter using plastic water bottles, you can crush up some charcoal with a rock, put it inside a piece of cloth, then run the water through it.  You can add some sand on top of the crushed charcoal to add another of filtration if you’d like.

Things To Consider When Using A Charcoal And Sand 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 and placing the pre-filtered water over the first to boil.

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.

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

Bio-sand Water Filters

If you don’t have any activated carbon, or you can’t build a fire for some reason to get charcoal, using sand and gravel as the filtration media to pre-filter your water is better than nothing.

It’s a very primitive filter that’s designed to get rid of the turbidity, so you will have to boil the water afterwards, but it will help get your water much cleaner.

Just like the charcoal and sand filter, the bio-sand filter is going to depend on the emergency situation you are in.  If you find you and your family on the move, you are going to have to improvise and use materials that you can find or hopefully you’ve thought of water ahead of time and brought some items in your bug out bag to make a primitive water filter.

On the other hand, you may be stuck inside for weeks or even months without power.  If you have the time to build a more elaborate bio-sand filter for you and your family, then you might want to build something more permanent.

Typically, the bio-sand filter (BSF) is a simple household water treatment device, which is an innovation on traditional slow sand filters specifically designed for intermittent use. A BSF consists of a concrete or plastic container filled with specially selected and prepared sand and gravel.

The bio-sand filter is very popular in third-world countries and has provided clean drinking water to millions since the bio-sand filter’s introduction.  The particular bio-sand filtration system that is used in third-world countries is a little more elaborate than you might have if you are stuck out in the wilderness, but the concept is still the same.

Shungite To Filter Water​

Shungite has been used for centuries to filter water, but it’s even purposely used to make shungite water, which is thought to have healing properties to the body.  It is a black, shiny, mineral rock that consists of 98% carbon, which is why it makes for such good water filtering.

Shungite is only found in the region of Karelia, Russia and can be used as a natural water purifier as it removes almost all harmful microorganisms, metals, bacteria, and organic compounds from the water.

Even though the mines are exclusively in Russia, you can find the rough stones sold on Amazon or on other websites.

Final Thoughts

I hope you’ve learned the difference between purification and filtration of water by reading my two posts.  If you didn’t get a chance to read my first article on this subject, please make sure to read it as an important supplement to this one.

There are a few other ways to filter water that weren’t mentioned here in order not to make this article too lengthy.  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 boil it.  Just because you’ve pre-filtered it to remove the dirt and cloudiness doesn’t mean it’s safe to drink.

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.

Lisa grew up on a small cattle ranch in Madera, California, which is nestled in the heart of the largest agriculture cornucopia in the world. She runs a survival blog where she writes about her interest and helps people understand what’s necessary to prepare for emergencies. Only 2 hours from Yosemite National Park, Lisa grew up camping, bird hunting, fishing, and hiking. When not writing about her outdoor survival passions, you can find her working out at her crossFit gym, walking her two dogs, camping, fishing, skeet shooting, or hiking somewhere in the mountains.

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