Skip to main content

Water Acquisition and Purification

In this blog we will be looking at the importance of water in an outdoor environment, water intake and dehydration, a few ways of sourcing it, the 5 water contaminants and a few different methods of purifying it to make it safe to drink. We will also look at why having a metal container as part of your kit is so important.

Water Intake

The rule of 3’s (a flexible guideline) tells us that after first aid (3 minutes without air) and shelter (3 hours without shelter) that the next priority of survival is water (3 days without water).

On average, the human body can only last for up to 3 days without water, however in a hot and humid environment such as northern Australia this could be much less!

In a temperate environment the human body will use up to 2-3 litres of water per day just in normal bodily function (not doing anything) and 3-5 litres per day in a hotter climate.

If you were moderately active in a temperate environment you would need to drink 3-5 litres per day and up to 10 litres in hotter climates. Your clothing and exertion levels will also affect your water requirements.

If you are low on water, it is a common misconception that you need to sip your water in order to conserve it. This is NOT the case. If you only have a finite amount of water and you sip it over long periods, your vital organs including your brain will not get the water they require.

The loss of just 2 litres of body fluid without replacing it will impair your ability to think clearly and perform simple tasks by as much as 25%.

Drink your water in 200-250ml amounts at a time, do not sip it!

The water is much more valuable in your body than in your water bottle.


If you are reasonably hydrated, you should be producing at least 1 litre of clear to straw coloured urine per day. The more dehydrated you are, the darker the urine colour and the output less.

Thirst is not a good indicator of dehydration. By the time you are thirsty, you are already dehydrated so drink before you get thirsty.

Other causes of dehydration include: the environment, moisture loss through perspiration and breathing (2-3 litres per day can be lost this way), vomiting and diarrhoea and failing to drink enough.

Signs and symptoms of Dehydration

Thirst, headaches, dizziness, tingling in limbs, irritability, reduced urine and saliva output, dark urine, reduced good decision making, muscular aches and pains, nausea. If these symptoms are left unchecked, they can further deteriorate and lead to heat exhaustion then turn into heat stroke which is a life-threatening condition.

Avoiding Dehydration

Drink enough (200-250ml at a time), avoid extra strong diuretics such as espresso coffee (normal strength tea and coffee are ok in moderation), carry sufficient water and a means of purification, fill up when you wake up, have adequate salt in your food, take advantage of all good water sources.

Conserve your sweat, not your water. Do not sip water, drink in 200-250ml amounts.

Water indicators and finding water

Other than the water that falls from the sky and other obvious water sources such as rivers, creeks and streams, finding water in an otherwise arid dry environment is another story, far too detailed for these few pages.

Terrain: The shape of the land can be a help when finding water. Water runs down hill so any low lying areas are going to be a possibility.

Vegetation: Verdant green vegetation in an otherwise dry area could be an indicator that water may be underground particularly if it is a low lying one. Certain trees that only grow in areas where there is usually fresh water are also clues eg. Pandanas, Melaleucas, Casuarinas. Some jungle vines such as the native 5 leaved grape  (Cissus hypoglauca) can be cut and the water drunk as is. The water must be clear, odourless and not milky.

Insects: Insects such as bees, wasps and dragon flies never stray too far from water. Observing their behaviour, such as wasps building a mud home could be a clue that water is in the area.

Birds: Grain eating birds such as finches never stray too far from water. I have personally used this when in the Pilbara on an army exercise where we were low on water after a long stomp and made camp after dark. The next morning I heard finches, followed the sound and found a small soak hole 200m away.

Animals: All animals need to drink just like us. Animal tracks converging on one another to form larger tracks that lead down hill are a sure sign that water could be in that direction.

Drinking water from the native 5 leaved grape vine (Cissus hypoglauca). The water must be clear, odourless and not milky for it to be safe to drink.

Water Collection Methods

There are various ways of collecting water, each requiring some form of receptacle or sponge to collect it or soak it up. These include various sized water bottles, containers and cups to collect water from obvious sources such as rivers, streams and water holes. Plastic sheets, garbage bags or tarps to collect run off from rainwater and cloth or clothing to be stuck into hard to access holes or cracks to soak up water which in turn can be rung out into a container. Cloth can also be used to collect early morning dew from vegetation and smooth surfaces.

If you don’t have a receptacle or method to soak water up you are going to have to find or produce something from nature which requires some ingenuity and also can be quite time consuming.

Once you have collected your water, you now need to make it safe to drink.

All water sources should be considered as polluted.

A poncho used to catch rain water

Input vs Output

It is also important to note that when you are low on water you do not want to exert more energy and water loss through perspiration than you need to in order to obtain water.

Some methods of obtaining water such as the “Solar or Desert Still” which is well documented in many survival books in my opinion is one of the most ineffective methods of obtaining water as you use up more water constructing the apparatus than you get back from it.

Water Transpiration Bag

One of the most effective and energy efficient methods of obtaining water in Australia and one I use often is the Transpiration bag.

Take a large heavy duty “clear” plastic bag (a black plastic bag will not work) and place it over a leafy branch or sapling of a non-toxic tree. All Wattles (Acacias) and gum trees (Eucalypts) are safe choices in Australia and are widespread and common. Select a branch that is predominantly in the sun all day (north facing below the Tropic of Capricorn). Tie the bag off at the mouth, creating an airtight seal and ensuring a corner of the bag is at the bottom.

Plants and trees draw up moisture from their root system and disperse the moisture into the air through their leaves. We are capturing this dispersal of moisture inside the bag where it condenses. As the water vapour and droplets get heavier, they run to the bottom of the bag. It’s possible to collect up to 700ml of water from one bag in a day. It all depends on the aspect, size of sapling/branch and area. Every tree will be different. The water produced may have a slight discolouration to it caused by the tannins in the leaves but it tastes great and is drinkable straight away. It is best to consume the water produced through this method within 24 hours and to change branches after 48 hours so as not to damage the tree.

Transpiration bag over a Eucalyptus    

Collecting the yield. This is immediately drinkable and does not need to be purified.

The 5 Water Contaminants

There are 5 contaminants that pollute water that you need to know about in order to make your water safe to drink.

Turbidity – is the measure of relative clarity of a liquid. Cloudy, hazy or muddy suspended particulate matter such as sand mud, silt or other decomposing organic material must be removed first through filtering for all water purification methods to be able to work. Even if there are no pathogenic (disease causing) organisms in the water, turbid water can still irritate your stomach.

Parasites – are microscopic organisms that live on or in another host organism. They can be either single cell organisms such as protozoa and cysts or multicellular organisms such as worms.

Protozoa are parasitic or free-living organisms that are able to multiply in humans and other animals causing disease. Eg. Cryptosporidium and Giardia.

Bacteria – much smaller than parasites, bacteria are single celled organisms found almost everywhere on earth (in the soil, water, in the air or in the tissues of plants and animals). Some bacteria cause disease while others don’t. The ones that do, produce a wide range of infections, some of which are potentially lethal. Eg. Typhoid Fever

Viruses – a virus is a sub-microscopic infectious agent (not a cell) that replicates only inside the living cells of an organism. Still smaller than bacteria, viruses infect all types of life forms including animals, plants and other microorganisms. Eg Hepatitis A, Polio, travellers diarrhoea and viruses in the water from poor sanitation.

Chemical Pollutants – pesticides and heavy metals from man-made polluting sources such as mining and agriculture.

Filtration and Purification

Once you have collected your water you need to know how to filter it and purify it in order to make it safe for consumption.

There are many methods and gadgets on the market that either filter or purify your water, some do both. Not all methods treat everything, some treat some pollutants but not others and vice versa so you need to know what you are dealing with.

The main water treatment methods are: Coarse Filtration, Microfiltration, Chemical Sterilisation, Ultraviolet sterilization, Boiling and Activated Carbon.

Coarse Filtration/Pre filtering

Coarse filtration using a Milbank bag/Brown Bag, bandana or piece of thick cloth removes turbidity and sediment and is the first stage in treatment for all methods.

Coarse filtration potentially reduces the load of pathogenic organisms if attached to dirt etc, however It does not filter out even the largest pathogenic organisms directly.

Coarse filtration is needed to make water clear so that chemical methods work more efficiently.

Coarse filtration using a Milbank bag to get rid of any turbidity before sterilisation

Coarse filtration using a bandana or piece of cloth


Microfiltration using a ceramic filter, pump or gravity system removes larger pathogenic organisms such as protozoa without having to resort to heat. It is not as effective for smaller bacteria and viruses.

Chemical Sterilisation

Chemical sterilization methods such as chlorine, iodine and chlorine dioxide have various pro’s and con’s.

Chlorine: pH sensitive, temperature sensitive, deactivates bacteria and viruses but needs clear water, does NOT kill protozoan cysts, inexpensive, no contraindications.

Iodine: works on turbid water, will kill most protozoa (not as effective on cryptosporidium) in addition to bacteria and viruses, limited shelf life, contraindications (don’t use longer than 28 days, don’t use if thyroid problems, do not use if pregnant).

Chlorine Dioxide: kills ALL pathogenic organisms but is expensive, unstable in solution and needs to be mixed prior to use as per instructions, needs to be used within allotted period of time.

Potassium Permanganate: Potassium permanganate (Condees Crystals) is widely used in the chemical industry as a strong oxidizing agent and is also used as a medication for dermatitis, for cleaning wounds general disinfection and treating water (used in wells to control iron bacteria and other biological growth. It also keeps well waters taste and smells under control). Place 4-5 crystals only per litre until the water is a very clear light pink, wait 30 mins. PP is on the World Health Organisation Model List of Essential Medicines. Sensitive to temperature extremes, performs best between 10-22 degrees celsius. Poisonous and irritates the skin.


Ultraviolet devices available can safely purify clear water and eliminate up to 99% of water born pathogens including protozoa, bacteria and viruses. Water must be filtered and clear for these methods to work. Any electronic device is also subject to battery life and breakage in the field.

Activated Carbon

Activated carbon filters are the only way of getting rid of most chemically polluted water.

They remove pesticides, herbicides and many other toxic chemicals such as dioxin, benzene and styrene. AC does not remove all chemicals or smaller pathogenic organisms.

Activated carbon also removes tannins and phenols which improves taste and smell. It also removes chlorine so use AC first!


Boiling water is the simplest and most reliable way of making water safe to drink. Boiling kills all pathogenic organisms but does not remove chemicals. A rolling boil for 1 minute at sea level is all that is needed to make water safe to drink. Water boils at a lower temperature the higher you go in elevation so boil for an extra minute for every 2000ft. The only drawback of boiling is that it requires fuel and time.

Having a metal container and nesting cup as part of your kit so that you can boil water is essential. Klean Kanteen make a good variety of stainless steel water bottles. Get the single walled variety, not the insulated bottles or you will burn a hole in it.

Another option is an army water bottle and metal cups canteen that fits onto the bottom.

A SS container and cup is an essential piece of kit. A rolling boil for 1 minute will kill 99% of water born pathogens

If you don’t have a metal container, you will have to make a vessel in nature that can hold water and allow you to boil water using hot rocks (hot rock boiling).

Boiling water in an improvised container using hot rocks

Water treatment options

  1. Coarse filtration → Boiling
  2. Coarse filtration → Microfiltration –> Chemical sterilization (chlorine, iodine or chlorine dioxide)
  3. Coarse filtration → Chlorine dioxide (1st choice) à Iodine (2nd choice)
  4. Coarse filtration → Ultraviolet device such as a SteriPen
  5. Coarse filtration → Microfiltration + Activated Carbon (chemical pollutants) à Chlorine

Milbank bag, SS container and cup, chlorine tablets, Vial of Potassium Permanganate, SteriPen, Grayl Water Purifier

  1. With 3% of solar radiation being Ultraviolet, you can put a clear plastic bag, glass or plaztic bottle in direct sunlight for sterilisation also.

    • Edit: Plastic not plaztic.
      And of course the bottle or bag must actually contain the water you need to sterilise.

    • Yes, this does work but it needs to be in constant sunlight (not overcast) for a 12 hour period, ideally 24 hours for it to work more effectively and even then it is not as effective as the other methods mentioned. I consider this to be a fall back method if the other methods are not possible. Thanks for reading and thanks for the question.

  2. This is a good article Gordon, very informative.
    I’m currently doing this topic with Paul. I’m not sure why Paul dose not mention PP in his course.
    I think the Millbank bag is underrated piece of lit these days with everyone relying on the life straw microfilters, the straws are defiantly worth there weight but you can get much more out of them if used in conjunction with MB. I store all my water filtration gear inside my MB.

    I look forward to your next blog

    • Thanks for the question Justin. Potassium Permanganate is used for sterilisation but it is less effective than the other methods mentioned. It is also hard to come by these days, especially at the moment. I have it in my kit for all the other uses it has (antiseptic, anti fungal, fire etc). Have you asked Paul his thoughts on this?
      The Milbank bag is definitely underrated and it is sad that the army are phasing it out. Most modern soldiers don’t know what it is let alone how to use it!
      Yes everyone is heading for the LifeStraw and Grayl water filters these days and they work very well and are a one stop shop that take care of everything, but like sleeping in a tent (bubble) all the time and not interacting with nature the way you do with a tarp and learning about water shed principles etc, or relying on a GPS with no map and compass skills, they don’t really teach you anything about the various individual water contaminants or what to do if you don’t have the “goochie” device or if it fails to work.
      Thanks for the question and thanks for reading Justin.

  3. Excellent article Gordon!

    Do you have any tips for getting the water out of a transpiration bag without damaging it?

    • Hi Craig, you can either take the bag off the tree and tip the water out which is drinkable straight up (if your tree selection was correct), then put the bag back on the tree (don’t use the same branch for more than 2-3 days) or you can put a small hole in the reservoir at the bottom of the bag with a knife where the water has collected, drain it then seal it by tying it up with some string so that it goes back into production again.
      Thanks for the question and thanks for reading.

  4. I think it’s a good idea to stress NOT to use a black plastic (aka garbage bag) as I was taught it makes poisonous gas, or can in some spp in North Aust (iorn wood?). However, I did try and fing a reference for this with no luck.. so maybe it’s a myth?

    • Hi Michael, the article does mention to not use a black plastic bag as it simply does not work as the plant needs sunlight for photosynthesis to take place.
      A non toxic tree should also be chosen and why I suggested selecting Eucalypts and Acacias in Australia as they are safe, widespread and common. Sure there are many toxic trees out there but to mention them all (if known) would be tedious as this was only an overview. In another article focused on this we will go into more specifics.
      Thanks for the question and thanks for reading.

    • Thanks for the positive feedback Joe, I’m glad you enjoyed it. Thanks for reading.

  5. Thank you for your article,this is something I can remember & now understand alot better despite
    having read various bits on the internet. There seem to be various types of portable water purifiers ( I like to do multiday hikes,previously used a tablet fairly short expiry & “micropur forte water disinfection”_troclosene sodium& silver) but I would like to look at something else.Do you have a preference for Grahl ? I hadn’t heard of this one. If so any particular reason the grahl?

  6. G’day BSA, i was wondering how to bind the bangalow palm or say cocos palm together as a carrying device for water. does it need to be relatively green? i only noticed one device at a recent course and didnt get the chance to ask or inspect.

Your Email address will not be published.