Sunday, January 22, 2012

Basic Survival: Basic Field Expedient Water Purification Methods

Song:  In The Morning Light

Artist:  Yanni

In case you have you not already read the initial article explaining important concepts...
read the following article first:

I have two basic objectives in this article:
(as my focus is on equipment for the Bug Out Bag...
I'll save the methods of water location for later articles)

1)  To have you pre-plan in the stocking of at least two viable water
filtration / purification pieces of equipment for your Bug Out Bag.

2)  To give you the basics of water filtration / purification 
through a field expedient improvised method as a backup
for equipment failure or loss.

Having a source of clean water is absolutely vital.

Under extreme exertion and climate conditions...
your need for water, to prevent death by dehydration...
 for a normal healthy person...
 is measured in just a few days.


There are two extremely important points I must emphasize:

1) You simply MUST be able to secure potable water...or you SHALL DIE.

2) You simply MUST be able to secure potable water...or you SHALL DIE.

I hope that was clear enough.


I will cover some very basic methods of water 
filtration / purification that are frequently used by portable water purifiers.

Note:  You must research on your own as to the use of particular brands...
they vary widely in price.  I purposely did not include a direct link to these products
as I do not wish you to believe my advice to be tainted by financial gain.

You must plan on at least two separate pieces of equipment for water purification
for each person...
it is simply too important not to.

1)  Mechanical Filtration:  Using various mediums of decreasingly
smaller holes, or avenues of passage (permeability)...
to filter out increasingly smaller particles
(including cysts and bacteria).

They usually start with a fine screen of some sort
and advance through increasingly fine materials 
until reaching an ultra fine ceramic filter or a
block of activated charcoal.

Some good examples:

Relatively inexpensive and effective.

Not so expensive...
higher output and can use to store purified water directly into containers of your choice.

Effective and very inexpensive.
Lightweight and small.

Although you cannot really use it to store purified water into containers...
you could merely store and transport unfiltered water and use this on it.
This type of filter is a must have as a backup.

2)  Reverse Osmosis:  Technically, an ultra fine mechanical filter...
it uses a semi permeable membrane for its filtration.  

This unit also uses the grosser forms of mechanical filtration as 
a pre filter.  It would simply clog up too quickly without them.

An example:

Very effective...the best portable out there.
It filters to a much higher degree than the rest.
It is, however, relatively expensive and bulky.

As it uses a semi-permeable membrane and pressure to force the water through...
it is a Reverse Osmosis filter
(contrary to normal Osmosis where lower concentrate solution naturally diffuses
to the higher - the reverse process is used... hence the name, Reverse Osmosis...
the higher to the lower by unnatural means...
 outside pressure as applied by the pneumatic pump of this apparatus).

Note:  While Reverse Osmosis is one method used to desalinate water...
it takes an extraordinary amount of pressure (up to 1200 psi).
This unit simply cannot generate the force necessary to do so.
Although there exists portable units that can desalinate water 
by various means (including Osmosis)...they are either cost prohibitive...
or take too long to produce appreciable amounts...
you could just distill instead. 

If, however, your live in an area that has extensive supplies of brackish 
or other high salinity water sources, including the ocean...
then a portable desalinator is a must.

of all the portables not used to desalinate...
 this has the smallest pore size...
and so, filters out even viruses.

If you can afford it...
this is the gold standard for portable water purification.

3)  Ultra Violet Sterilizers:  To be used only after one of the above methods
 (although not necessary).  

There are simply too many variables that can affect 
the efficacy of such a method...besides being inherently
unreliable in the power source and bulb as a prime method
(Should the water be won't work...
time of exposure...must be enough...etc).

4)  Chemical Purification:  Chlorine, Iodine or other types commonly used
as tablets or liquid drops to add to your water containers.

A good third back up...however, you should use some sort of mechanical
filtration method first (at least straining through a t-shirt).

Very inexpensive, lightweight and small to carry.


Some commonly used field expedient methods to purify water
when no other methods exist (no specialized equipment such as the above).

1)  Boiling - A time tested method of killing various pathogens...
such as bacteria, viruses, protozoans...etc.

There are, of course, drawbacks to such a method as a primary 
means of water purification on the move (base camp fine).

You must have the fuel, container to boil it in, and the time to build the fire...
and to boil enough to store.  You will also lose some in the boiling process.

Know that in order to be safe...
you must bring the water to a ROILING boil for at least 1 minute...
at sea level.

As altitude lowers the boiling point of water from that at sea level
(approximately 2 - 3 degrees for every 1,000 ft in elevation)
and it is the time spent in temperature that kills the pathogens...
then 2-3 minutes should do the trick.

Also know that a relatively large container and a lot of fuel
will be needed to fill an appreciable amount of water to store and carry.

Even without special equipment to boil water...
ones can be made with a minimum of vegetation.

The whole idea is to have a container to hold the water while the water boils.

This can be effected by broad leaf plants...
even by the bark of trees.

You needn't worry about burning away the container,

So long as the heat source is not too concentrated on any one area...
or the material so thick as to not be able to conduct the heat directly to the water...
the water will absorb the heat and boil and keep the material below the point of ignition
(stay away from plastics - most breakdown in heat).

That is precisely why you can boil water in a paper cup while held directly over a flame.

2)  Simple Steam Distillation - This method can be used to effect desalination as well as 
for removing many undesired impurities from water.

However, you must realize that simple steam distillation does NOT
make the water pure.  It only keeps anything that does not 
volatilize at, or below, the point that water does... out.  
Its basic function as a field water purifier is for desalination.

Example: You cannot get water which is heavily contaminated with certain petroleum
compounds and expect drinkable water from it.  The contaminates would evaporate
and re-condense along with the water.

All Simple Steam Distillation is...
is a method of boiling a liquid (this case...water)...
and having it re-condense on to a cooler surface for collection.

As this is a more lengthly and effort inducing process...
it is more appropriately done at a camp.

This takes the most equipment, time, effort, and fuel... 
of the basic methods of water purification.

The only real piece of equipment that is not normally included
in a Bug Out Bag would be the condenser coil or hose.

This is easy to get off of your vehicle were you to be stranded...
you could make your own from the environment...
or you could merely have the steam condense on any cooler 
surface and directed into a container.

Just think tube from a flat pliable surface (roll from items in your bag)...
or from vegetation or bark
(it must be long and cool running enough to convert the steam back into water).

For large amounts of water to fill containers...
any center indented dome large enough to cover the pot
(best done when it is cool)
with a catch container hanging below the indentation 
and from the sides...would do
(easily made from tarps, ponchos...even wide leaves...etc).

You could also easily dig on an incline...
a trench which you could line with flat rocks...
and the trench capped with flat rocks
(if it is long enough...the end may also be capped)...
with the boiling water at the bottom entrance.

The steam would rise in the cave or long tube...
condense on the rocks...
run down to be collected
(with the tube end uncapped...
this could also be used to preserve large amounts of meat...
as a fire at the base without the water pot... is a chimney oven.
Obviously...if you are to do both...purify the water first).

So long as you know the principle of the condensation of steam
onto a cooler surface that could collect the resulting water into a container...
you could then improvise from the environment to desalinate brackish or seawater.

3)  Evaporative Still - This is the same as the Steam Still except that it does
not involve the use of high temperatures.  It commonly involves using the sun.
It is commonly called a solar still and is also used at sea as an emergency device
to desalinate sea water in case of dire emergencies necessitating taking to a life raft.

It is not terribly efficient and the amount of water collected generally does not
justify constructing them.

4)  Ultra Violet Radiation/Solar Heat - 
So long as you have a container that is no deeper than a few inches...
(a plastic soda bottle lying on its side with full exposure to the sun)
and is capped to prevent the evaporation of the water to be purified
(this method will NOT desalinate)...
and is fully exposed to the sun for at least 6 hours...
tests have shown a dramatic reduction in pathogens to levels
which would be far safer than not purifying at all.

Not the preferred method since it is not nearly so safe as is boiling...
besides the wait time and the large number of smaller containers necessary...
unless you could construct something from your surroundings
( large clear plastic bags with 3-4 inches of water depth with the bag
allowed to spread out).

The main pathogenic destroyer is the UV-A rays...
so the principle is for transparency of material...
and limited depth of water.

The solar heat helps kill the pathogens...
it is not the major purifier.

Just something to keep in mind...just in case.

If you don't get anything else from this article...
as you can see...
it would be FAR wiser...
efficient and effective...
to get some good water purifiers before the need arises...
instead of having to improvise in the field
(not always possible).

Never doubt the need for clean water...
or the difficulty of extracting it from your environment
should there be no readily apparent sources available
(and so the need to have containers to transport that which you do find).

I have given you just some of the very basics of field water purification.

That is only one third the equation to prevent dehydration
(unless there is always a supply at hand to purify...rare).

The other two will be covered in later articles
(finding/extracting water from the environment...
and the storage and transportation of it).


  1. I am learning a lot from this series of posts. You should have your own outdoor survival show!

  2. Thanks...but it really is only the very basics (I am, by no means, an expert).

    I am, however, very glad you find the articles interesting. Basic woodsmanship is a great opportunity for children to build trust in the parent, and teaches the children the importance of proper prior planning.

  3. Hiya, I'm really glad I've found this info. Nowadays bloggers publish only about gossips and net and this is actually irritating. A good web site with interesting content, that's} what I need. Thank you for keeping this web-site, I'll be visiting it. Do you do newsletters? Can't find it.
    Custom Leathercraft 1134 Tool Backpack, 48-Pocket

  4. Thank you for commenting. No, I do not do any newsletters. I am just a retired dad blogging about his 2E son and about basic concepts of raising not only survive...but to flourish.


Please feel free to comment on this article.

Related Posts Plugin for WordPress, Blogger...