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Home » WATER, WATER NEVERWHERE Part 5: How To Clean and Filter Your Own Water

WATER, WATER NEVERWHERE Part 5: How To Clean and Filter Your Own Water

WATER, WATER NEVERWHERE Part 5: How To Clean and Filter Your Own Water

By now you have found, identified, and gathered up your grey (not drinkable) water and brought it back to camp.

NOW what? You still can’t drink it with all those gross floaty things in it- you can’t drink it even if it doesn’t have gross floaties (because most illness-borne organisms are microscopic and you can’t see them), either.

So, FINALLY, the blog entry you’ve all been waiting for: HOW TO FILTER AND CLEAN YOUR OWN WATER, Part 5 in a series on procuring your own water in a survival situation.

The best way to fully understand how to turn dirty liquid into clean water is to first take a look at how our major cities process their water, and what exactly that fancy equipment does.

Afterward, we can pare it down to effective small-scale manual treatments, sure to provide a personal supply of clean drinking water in any situation.

(Read the entire “Water, Water Neverwhere” series for more detailed information like proper water storage containers, how to locate hidden sources of water, etc.)


Most modern American water treatment plants nowadays use three consecutive methods of processing the grey liquid to supply clean, fresh drinking water to the population.

These basic processes are, in order: physical filtration, chemical sanitizing, and UV radiation.

Different companies and areas of the country might have deviations to this, such as adding Fluoride to city tap water, but there is always some form of these three steps at the cornerstones of their processes.


Physical filtration is always the first step in purifying water. If you think it as not one but a series of filters for the water, beginning with removing the large chunks of dirt then ending with cleaning out the smallest microscopic impurities, you are right on track.

Filtering before disinfecting the water makes logical sense. There is no sense in chemically disinfecting grungy waste water when the water still has gross floaties (animal waste, trash, etc.) in it.

I don’t care how much bleach you put in the water; I don’t want to drink it if it still has chunks of dirt in the bottle! Disgusting!

The initial physical filtration is just that – physically removing the other stuff floating around in the water. It’s almost more of a pre-filtration, and can be considered a preparatory step.

When combined with more aggressive treatments, such as charcoal, evaporation and reverse osmosis, the physical filtration is almost all that is needed for clean drinking water -almost.

The most common and well-known substance used in water filtration is activated charcoal.

After skimming the dirty water for the largest, most obvious pollutants (such as trash to undissolved dirt), the water is then passed through a series of smaller and smaller pieces of active charcoal, thereby straining out the bigger contaminants first.

Using charcoal has many benefits, including the ability to absorb certain contaminants that are attracted to carbon. It also soaks up any odor and color from unwanted deposits in the water.


In a survival scenario, an opportune way of translating this information into manual physical filtration is simple.

A graduated container using large rocks at the top near the entrance, medium-size stones in the middle, and tiny pebbles and then sand at the bottom, will filter out many impurities and produce cleaner water ready to be chemically disinfected.

For best results, layer two or three cycles of stone/ pebble/ sand filtration. If you are lucky enough (or planned ahead well) to have a supply of activated charcoal or pre-made charcoal water filters, layer it beneath at least one whole cycle of rock/sand filtration so it saves on the charcoal.

If you do not have charcoal, use several layers of clean stone and sand, and – if possible – try to use an untouched water source, like rain (unless absolutely necessary, do not place rain barrels beneath a lot of trees or branches.

The water run-off from trees carries with it all the germs from the critters living in those trees, from squirrel poop to termites to tree fungus). Follow up with chemical sanitization before drinking.

Rain barrels, plastic bags, even an upside-down empty soda bottle with the end cut off will work as your graduated container.

Just put a large opening at the top to pour in the dirty water; and make small openings in the bottom for the newly-filtered water to drain into a clean container sitting beneath.

This way, the force of gravity alone powers the filter. See picture for a visual example- you will notice that they have two filtration cycles of stone and sand layers, then charcoal at the bottom.


If, for some reason, you don’t have a way to filter the water through a container like the one pictured, a messier alternative is to soak the water in the charcoal.

First, pre-filter the water by pouring it through a piece of cloth into a pan and add charcoal. If you have the means, you can boil the water with the charcoal in it for 10 minutes.

The charcoal will chemically bind to the contaminants. Set aside the charcoal-soaked water for a few hours and let the solids condense and settle at the bottom of the pan.

You can then decant the filtered water (pour it off from the top), leaving behind the charcoal-bound clumps of nastiness.


If you have a still, or the means to boil water and collect the steam, this will work very well to physically separate contaminants from the water.

This will also help remove salts from the finished product in the case of being stranded at sea, by the ocean, or any other body of salt water (Do NOT drink salt water, no matter how thirsty you are. It will only make things worse).

A fairly accurate portrayal of using the sunlight itself as the heat source to distill water is done by Robert Redford in All Is Lost, an excellent survival-related stranded-at-sea movie.

In a dire emergency, drinking the purified steam of water may save your life.

However, since water boils at 100 degrees Celcius before turning to steam, this will only kill off the microorganisms that can’t survive heat under 100C, leaving other infectious heat-loving organisms, called thermophiles, alive.

Therefore, it is recommended you still chemically treat the distilled water before drinking unless absolutely impossible.


Besides charcoal, industrial water plants add chemicals to bind to tiny impurities like bacteria, then add more chemicals to dismantle and dissolve away those first chemicals.

Fortunately, chemically sanitizing water – if the water is filtered well enough – can be as easy as adding a small amount of chlorine bleach or iodine. Let the water and chemical mix for at least 30 minutes before consuming.

(More information on adding chlorine and storing the water in a safe container are discussed in Part 1- Storing the Water. Read the entire blog series for further information.)

In most military and military-style survival packs, it is recommended to include a prepared water treatment, like iodine or charcoal filters.

In that case, after physically filtering the water, follow the directions that came with that specific filtration system.

Fortunately, technology has come a long way, and premade all-in-one filters such as “lifestraws”, personal water filters, etc. are now available in the retail market and adventure stores (ahem, like our own website right here;

Mike’s Military Surplus, Camp & Prep Supplies. Of course we carry some pretty severe water filters, so you don’t have to go through all of these above steps *shameless plug*)


In the latter part of last century, metropolitan water plants began adding this 3rd step of exposing the treated water to UV (light) radiation.

If the word “radiation” scares you, don’t worry – any time a ray of visible light is emitted from a source, it is called radiation.

If that still brings to mind thoughts of cancer or mutated cells, you are thinking of a specific type of irradiation which directly penetrates the body’s vulnerable cells and ionizes them, mutating the DNA.

Irradiating the skin with too much sunlight alters the chemical composition and can give you melanoma.

Since water is a simple chemical with no DNA, irradiating the cells simply leaves you with ionized water, which is fine to drink.

You can’t become “second-hand ionized” by drinking ionized water; you are in much more danger getting sunburnt. So, wear sunscreen, but drink the water.


Unless you are without any other means to sanitize your drinking water, do not use radiation exclusively when dealing with grey or untreated water. You must first complete the two steps of physical and chemical filtration.

UV rays will only rid the water of living bacteria, viruses, and other microorganisms with a genetic code (E.coli, cryptosporidium, giardia, etc.).

It will do nothing about contaminants such as VOCs (Volatile Organic Compounds), salt, lead, and other heavy metals. Do NOT just take unclean water and set it out in the sun!

Unfortunately, successfully irradiating water with UV rays is difficult and unreliable when doing it yourself without any standard equipment.

First, the UV light must pass through only a very thin layer of CLEAR water in order to penetrate it completely and effectively. Imagine one shallow cookie sheet of water at a time.

Second, a reliable source of UV rays used (in order to maintain consistent irradiation for a given length of time) is usually a man-made device such as a UV lamp, or mercury vapor lamp, set to a specific wavelength of light (a “germicidal frequency” shorter than visible sunlight) , with a sustained source of electrical energy with which to operate.

In these cases, the light is passed as close to the water as possible (without getting the electric light wet!) in order to penetrate fully.

Yes, there are battery-operated and handcrank-powered UV lamps for the purpose of purifying water, but it is important to keep in mind that you STILL must physically filter the water until clear before taking this step.

In all, you can skip the UV filtration entirely, as long as you are thorough with physically and chemically treating the rain/river water.

If you do want to purchase a UV lamp for an emergency or SHTF scenario, make sure you have adequate practice at it and a stable power source.

For a list of reliable personal water filters to be used while camping or in the case of emergency, see a list of water filters at our store’s low prices!

Read more of our blog on survival hacks, survivalist tips, military gear, or just fun lists and tricks here at our main blog page.

Shop our online store for military surplus items, camping supplies, and survival gear! Start here at our home page and select the categories at the top of the page.

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