Home Survival StrategiesFood & Water Improvising Filters to Purify Water

Improvising Filters to Purify Water

by Kyt Lyn Walken

We often underestimate the importance of having sufficient water supplies during all of our activities.

This is critical if caught up in an emergency situation, we not be able to make our way to a supermarket. Any hazard, really, could result from a shortage of supplies. Water first!

Having a good stock of water is mandatory, specifically if our intention is to spend several days in the outdoors. We should be able to rely only on the provisions we bring, purification systems, and our expertise as survivalists.

Even when the weather isn’t very sunny, our bodies need a supply of fluids adequate for the efforts we are making or the conditions we are going to face. Therefore, getting more than a bottle (or Camelback) is not just a matter of common sense, but also of prudence. And smartness, too!

The absence of springs, mountain huts, and so on can make us bitterly regret having underestimated our itinerary, and drawing water from unsafe sources can be a fatal mistake that we must necessarily avoid.

If we do not have any water filtration and purification system (although there are several on the market, and very good ones!), we can build one ourselves using just a half-liter plastic bottle and a piece of rope (or twine, or even a shoelace)! There are other methods for this too.

In this article, we will lift the lid on how to do that, resorting to some basic items we have inside our backpacks.

Purifying Water

Collecting water from any stream without processing it is a huge mistake we need to avoid. Even if we find ourselves hiking at considerable altitudes (13,123 feet or 4000 meters), we cannot just grab our canteen and start to refill it at the first high mountain creek we run into. It doesn’t work that way.

Without any safety procedure, a simple act like this can contain all the ingredients for a disaster.

Let me tell you about an experience I had several years ago.

I was hiking in the Dolomites, at 6560 feet. On my way up to a bivouac, I ran into a group of ten people led by a guide. The trail flanked a tiny creek. The guide invited his group to refill their canteens.

I observed the scene in silence and moved on.

When I was 320 feet away, I noticed the carcass of an ibex right in the middle of the stream. The carelessness of that guide might cause of serious disease for the participants he was supposed to take care of.

I have this episode stuck in my mind. The moral is very simple: you may never know what is—or was!—in the water you are collecting.

Sticking to the basic principle “better safe than sorry” could actually save your life. And others’ too! Or, at least, it could prevent you from getting a serious illness.

What is in Water

Bacteria live everywhere, from surface water to groundwater.

The presence of some bacteria can be harmful to our health, especially in subjects which are more at risk, like elderly people, or those who are over-fatigued.

Bacteria, along with parasites and viruses, can lead to some tragic consequences. Coliform bacteria, for example, is one of them. E. coli is part of this family.

This bacterium can cause nausea, diarrhea, cramps, vomiting, headaches, physical and mental fatigue, fever, and ultimately, it may cause even death.

Fecal matter surely contains many pathogens and bacteria too. If you approach a mountain creek with no doubt at all, please… step back and reconsider the whole thing. Ungulates’ urine, parts of carcasses, and the like are the real danger when you need to collect water.

Besides that, you can still make that water drinkable by resorting to some good, and reliable water filtration systems you may easily find on outdoor stores. Or you can use water purification tablets. The market is literally full of them.

But… what if you don’t have any of those?

You can still sort out the whole situation using some knowledge, basic handiwork, and, again… common sense.

Even if your gear is far from being cutting edge, you can still employ many very basic items, like a plastic bottle, to create your own purification system.

I learned this method – and put into practice – while attending the Conservation Ranger Course back in 2018 to become an Antipoaching Ranger. It was part of the survival program to volunteer as a ranger in the African continent.

Let’s learn more about that!

Purifying Water with a Plastic Bottle

It goes without saying that the initial water filtering process must be followed by boiling (for at least fifteen minutes per approximately 500 ml), in order to eliminate most of the viruses, parasites and bacteria which are contained, but before that you will want to filter out the particulate.

What you need:

  • Approximately 16 oz plastic bottle – empty
  • A cutting tool
  • A shoe lace, paracord, or a thin rope
  • A gauze cut in pieces

In order to create an effective filter, you need to cut the plastic bottle into two parts, about in the center. The bottom part will act as a reservoir for the filtered water from the top.

To make it effective, it is necessary to create different layers in the top part of the bottle (one made of sand, one of small stones or gravel, and so on), and, if possible, alternate them with gauzes, which will be able to retain impurities.

Strictly avoid a layer of leaves! The presence of tannins in them, will make the water impure and even toxic.

Once you have finished composing the different layers, make two holes in your bottle to pass the string through and hang it from a branch. Position the “cistern” below.

Pour the water you wish to purify into the filter through a plastic bag that you will throw in your garbage—leave nothing behind in nature!—and wait patiently, drop by drop, for your water to be ready to be boiled!

This method takes a little bit of work, but it also gives a plastic bottle new life.

Purifying Water with Distillation

By this method, you will be able to get some fresh water out of a very easy process. All you need to do is to dig a hole in the ground. Be careful to create a small hole – almost mug-sized – in the center, placing your canteen in it. Make sure to have a bigger surface around the bottom of your canteen then cover it all with plastic.

You can actually use a plastic bag to do this. Put a small rock right in the middle of the plastic sheet once you have secured the edges in order to prevent it from collapsing into the hole.

Then, all you have to do is… wait! The distillation system works through evaporation and condensation. If you put some green plants inside the hole, the pores will transpire and contribute water.

This process even work to desalinate water.

This method is the best way to go when you find yourself in an emergency situation and you have the ideal conditions to make it work like staying in one location overnight.

Purifying Water with Charcoal

In some cases, the employment of activated charcoal becomes the ideal water filter. In fact, it is able to remove toxins from the water without compromising the benefits of the water itself in terms of salts and important minerals.

By collecting some charcoal from your campfire with a canteen, you can pour some greywater through it, and then proceed with boiling the resulting filtered water.

Conclusion: On Natural Filters

Recent research about natural filters being employed in greywater filtration systems in Africa and Latin America investigated “…whether fibers like coconut husks, maize, and seeds remove chemical toxins from water, and if they could filter polluted freshwater the same as greywater.

It was found that there are “…natural fibrous components with the potential to purify greywater: activated charcoal powder, moringa oleifera seeds, and crushed corn cob. Charcoal powder has been used in greywater treatments before, and it can replace chlorine as a natural disinfectant; the seeds contain a protein with an antimicrobial effect in water filtration; and the corn has the ability to trap chemicals in its pores and soak in excess salts like calcium and magnesium.1


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