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HomeCampingBackpackers Guide To Finding and Treating Drinking Water

Backpackers Guide To Finding and Treating Drinking Water

Water is the stuff of life in so many ways. In fact, more than anything it’s you. 60% of your body at any one time is comprised of water; 73% of your brain and heart are water; 83% of your lungs are water (1).

It’s well known that people have survived for months without food whereas a lack of water will lead to dehydration and death in a matter of days (2).

It should go without saying that anyone heading into the wild should prioritise access to water when they plan their trip, but, be honest, how many of you have headed onto the trail, made it less than halfway to your target then realised you’re already approaching the dregs of your water bottle?

I certainly have.

Something about the ease with which clean water can be accessed in civilisation makes us complacent about H2O in a way that would have been unimaginable to our ancestors. Farms, towns, cities – indeed, many of the trails we walk – arose because of their proximity to rivers, lakes and other natural sources of drinking water. Finding water was once such a valued skill “water diviners” lorded it over the rest of society.

Since you probably don’t want to end up lost in the Arizona desert, hoping that you’ve inherited the gift of “water divining” as a requisite to survival, this guide should come in handy.

Okay, so how much water do I need?

The simple answer to this question is: a lot.

The exact amount of water you need in varies depending on height, weight, your level of activity and the weather conditions, but the current medical consensus is that the average male requires 3.7 litres of water per day and the average female requires 2.7 litres per day (3).

Head through to the fridge and lift out that two litre bottle of coke sitting in the door. If you’re a man that jumbo bottle represents barely half the fluid you should take on board in a day. If you’re a woman you’ll need those two litres and the best part of another litre on top of that!

What if I skimp a little, though? Is full hydration that important?

There are always those who like to cut corners and few things arouse the instinct to rebel like official advice. As satisfying as it is to flip a finger at “The Man” you’ll want to think twice about neglecting full hydration.

The Mayo Clinic note that we “lose water through (our) breath, perspiration, urine and bowel movements.” In effect, then, every time you breathe you are expelling water! If you sweat on the trail you’ll be losing even more.

WebMD list the primary effects of dehydration as “muscle weakness and cramping, a lack of coordination, and an increased risk of heat exhaustion and heat stroke.”

It’s hard to think of any combination of symptoms you’d want to experience less while trekking than these. The trail is a place for our bodies to peak in performance, not to fail. For that we need water.

Where to Find Water in the Wild

Litre-to-pound conversion websites like this one indicate that a litre of water equates to roughly one kilogram in weight. On that basis a man carrying the water he needs for two days would have to add add seven kilos to his pack. A woman would need to carry the best part of five and a half kilos.

One of the reasons many of us risk dehydration on the trail is a natural reluctance to carry the weight of water our bodies actually need. Fortunately, there is another way. Find your water in the wild…

Natural Rivers, Lakes or Streams

These are the most obvious sources of freshwater in nature and there’s nothing wrong with obvious. If your hike takes you close to bodies of freshwater that’s almost certainly going to be the easiest way for you to stock up on H2O.

Before doing so note that it’s always recommended that any water found in the wild is purified before drinking. This minimises the chances of picking up harmful bacteria from the water. For info on the various purification methods skip to Section 3 of this article!

Art of Manliness point out that, due to the bacteria risk, “clear, flowing water is your best option, as the movement doesn’t allow bacteria to fester.” As a consequence of this, streams are usually the pick of the three options since rivers tend to carry “pollution from upstream” and stagnant water (e.g. in lakes) can act as a breeding ground for bacteria.

How to Find Them

If you’re in luck this question will be redundant. Hiking trails often run alongside rivers or criss-cross fresh steams running down mountains/hillsides. Alternatively, you may already know the layout of the area you’re hiking and can plan your trip around its water sources.

What if the worst comes to the worst, though? You’re out in the wilderness with supplies running low and can’t find water?

Firstly, try listening for water. USA Today advise that you stand still for at least five minutes simply listening. Can you hear the rush of water? If so, move in that direction.

If that fails keep moving and keep your eyes peeled for animal tracks and/or clouds of insects. Both can indicate the proximity of water since insects tend to congregate around water sources and animals head there to drink. Follow the signs of nature like a tracker!

If all else fails head downhill! You don’t need a degree in Physics to know that water flows downhill so “chances are you’ll eventually stumble upon it if you keep heading into lower regions of the wilderness.” (4) Rocky areas on valley floors can be particularly promising since they can act as natural basins and trap water into pools.

Morning Dew

Looking to collect water in a more innovative way? How about going after dew? The Oxford Dictionary defines dew as “tiny drops of water that form on cool surfaces at night, when atmospheric vapour condenses.” Grass is a particularly efficient collector of dew and can be mined for dew in the early mornings.

Tactical Intelligence provide a step-by-step guide on how to go about collecting dew. Essentially, you want to grab something absorbent (a towel, t-shirt, etc), brush it across the dewy surface until it’s wet with dew then wring out the liquid into a drinking vessel.

A neat trick to impress your friends. And a potential lifesaver…

Collect Rainwater

Rainwater can be collected in the same way – soaking a cloth then wringing it out – but the classic method of collecting rainwater is more efficient and serves a dual purpose (5).

Large tarpaulins (which are virtually weightless and pack down to a carry-friendly size) can be strung from surrounding trees/bushes and – here’s the ingenious part – tilted at such an angle that any liquid that hits the tarp slides down the sheet and…into a waiting container.

The truly innovative could use the same tarpaulin as shelter from the rain. Imagine sitting beneath your tarpaulin as all the water that would otherwise be soaking you supplies fresh drinking water. Perfect!

Dig a Well

If none of the above is close enough to water divining for you then let’s look at something truly old school: digging a well.

The best location for a well is on a dried up riverbed or creek (6). The water may no longer be on the surface but, as this YouTube video shows, dig down with whatever you have to hand and you could soon be standing in a pool of fresh water.

Use the colour and texture of the soil to guide you. If the soil becomes darker and more moist as you dig down it’s an indication that you’re on the right track and water is likely present. Persistently dry soil should encourage you to try another spot.  

Plant Transpiration

Now we’re getting on to the really fancy stuff! Transpiration is the trickiest and most time-consuming method of collecting water and tends to be used only in dry, hot conditions. Trees have evolved to become highly efficient at accessing water. The basic idea of transpiration is to steal water from the tree!

In order to do so you’ll have to have with you, according to outdooradventureguide.co.uk, “a large, heavy duty transparent plastic bag, some cord, a tree/bush with a decent amount of foliage and plenty of hot sunshine.”

You’ll want to look for a leafy branch (branches producing greenery will have the most moisture), draw the bag over the branch and tie it tightly. Any moisture the tree “sweats” in the sun will thus accumulate in your bag.

Be sure to position your bag so that the bottom of it is free from contact with leaves. This helps prevent the water absorbing toxins from leaves as it gathers in the bag.

How to Purify and Treat Water For Drinking

You’ve done it! By hook or by crook you’ve collected fresh water in the wild. Before you drink to celebrate it’s critical that you treat the water to eliminate potentially harmful bacteria. There are a number of ways to do this:


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  1. Solar water disinfection

Solar water disinfection is a relatively new means of treating water and a handy one for the wilderness since, as the name suggests, the only resource you really need is the sun.

As the CDC explain, to treat water with this method you should gather it in a bottle, shake the bottle to oxygenate the water then leave it in the sun for a prolonged period of time to allow various UV-light inspired scientific tricks to do their work and purify the liquid.

A clear drawback of this method is the time it takes. Even on a sunny day the oxygenated water must sit in the sun for six hours before it’s safe. If the weather is overcast the process can take as long as two days!

  1. Purification Tablets/Drops

Water purification tablets make use of chemicals to kill off bacteria lurking in your water. Iodine, chlorine and chlorine-dioxide are the most common chemicals in these pills and have various plusses and minuses. Check out this guide for an in-depth breakdown of the types of pill on the market and how they compare.  

The major plus of purification drops, taken as a whole, is that they are extremely light and compact and can make water safe to drink in as little as half an hour. The downside, for many, is the taste – particularly the aftertaste – purification tablets can leave in water.

Fortunately, there are a few tricks that can be used to counter the aftertaste. Dropping an effervescent vitamin C tablet in the water after the purification pill has done its work can go a long way to neutralising the taste (7).

  1. Bleach

Household bleach can be (carefully) used to disinfect water. The amount of bleach you’ll need to add to water to make it safe for drinking will depend on how cold or cloudy the water is. Generally speaking, water that is cold and cloudy will require twice as much bleach to make it safe as warm, clear water (8).

Some bottles of bleach come with instructions stating exactly how the product should be used to purify water. In the absence of these instructions a table on the CDC website provides guidance on how much bleach to use per gallon of water you’re seeking to purify. Eg eight drops of bleach with a 5-6% concentration of sodium hypochlorite will purify one gallon of warm, clear water.

Once bleach is added to the water the containers should be shaken and then left in shade for at least 30 minutes. Only when the mixture smells of chlorine will it be safe to drink.

  1. Boiling

Boiling is the classic method of water purification. It is also the safest method, the “surest method to kill disease-causing organisms, including viruses, bacteria, and parasites” (9).

The longer the water stays at a “rolling boil” the more likely it is that any dangerous bacteria will be killed off (10). The minimum suggested period of rolling boil is one minute but expert sites suggest you’ll want to consider boiling for closer to ten minutes, particularly at higher elevations or when dealing with cloudier water.

  1. Distillation

Distillation is a process that transforms saltwater into fresh, drinkable water. If you’re hiking in an area where you can only find saltwater, distillation will be your go-to option since saltwater adds to dehydration rather than alleviating it.

In order to distil saltwater you will need two containers (one large enough for the other to sit inside it), a plastic bag with a cord to secure it and a rock (11). Fill the large container with saltwater then place the smaller container, its top sealed with the plastic bag, into the water. The rock should then be placed onto the plastic to submerge the smaller container.

Sit back and watch as the “water evaporates, condenses on the underside of the plastic, and runs into the middle container” (12). It might take a while but the magic of distillation could save your life!

  1. Straws and Pump Filters

Pump and straw filters are among the most hands-on ways to purify your water. An advantage of both methods is that they are quick but there are disadvantages, too.

Pump filters, as the name suggest, require you to manually pump water through a filtration device. They can be clunky and a little fiddly due to the number of parts they contain, but, if used effectively, can “filter upwards of 1.5 liters per minute” (13). In other words, two or three minutes of hard work can provide you with your daily allowance of clean drinking water.

As pump filters filter rather than purify (that is, they block pathogens but can’t eliminate viruses) it’s important to only use them in places where pathogens rather than viruses are the risk.

Straw filters are an even swifter means of getting water. True to its name this is a straw – and a very direct straw. With a straw filter all you’ll need to do to is bend down to a water source, pop the straw in your mouth and drink – the straw will filter the water on its way to your mouth!

Straw filters are lighter and more compact than pump filters. However, their chief advantage is also their chief drawback – they cannot filter water in advance, only as and when you drink. Additionally, like pump filters, they filter rather than purify water.

  1. Iodine

Iodine is a common ingredient in purification tablets but can also be used it liquid form. It should, however, be used extremely carefully and avoided, if at all possible, by pregnant women, people with thyroid problems and women over 50 (14).

Like bleach the quantity of iodine required will increase with the cloudiness of water. Five drops of 2% tincture of iodine should be added per quart of clear water to purify it; ten drops should be used if the water is cloudy.

The mixture should be left to sit in the shade for 30 minutes before it can be considered treated.

  1. DIY Filters

If you prize self-sufficiency above all else you can always have a go at making your own water filter. There are numerous guides on how to do so online. The beauty, as with most DIY projects, is that there are no real rules: make your filter your way.

Those interested in a filter that ticks all the boxes – cheap, efficient, portable, practical – may want to check out this LifeHacker guide on how to make an impressive-looking homemade “gravity” filter!

The dangers of drinking dirty water and water poisoning symptoms 

The CDC identify three main categories of illness that can result from drinking untreated water:

       Protozoa illnesses (such as cryptosporidium or giardia)

       Bacterial infections (such as salmonella)

       Viruses (such as enterovirus, norovirus and hepatitis A)

Many of these produce similar effects. Gastrointestinal discomfort that leads to cramping, nausea, vomiting and diarrhoea are the most common ill-effects of drinking impure water as the body tries to purge itself of ill-intentioned foreign bodies.

However, it is worth pausing to note that illnesses of a very different nature, hepatitis A and meningitis, can also be contracted from drinking backcountry water. No-one wants to be struck down by sickness and diarrhoea but gastrointestinal symptoms usually pass in a few days. Hepatitis and meningitis can have lifelong consequences and can even result in death (15).

Water Poisoning Symptoms

Protozoa (eg cryptosporidium and giardia)

Cryptosporidium is hard to say and even harder to endure. Mayo Clinic list the symptoms as watery diarrhoea, dehydration, lack of appetite, weight loss, stomach cramps/pain, fever, nausea and vomiting. These usually pass within two weeks but they’re unlikely to be the most enjoyable weeks of your life.

The symptoms of giardia are listed by the NHS as “smelly diarrhoea, tummy pain/cramps, flatulence, smelly burps (they may smell like eggs), bloating and weight loss.”

Bacteria (eg Campylobacter, Salmonella, Shigella, E. coli)

The names of these nasties should be enough to have you swearing off sipping directly from streams for life. Irrelevant of the name you can expect similar symptoms: diarrhoea, vomiting and cramps. Fever and blood in faeces are equally unpleasant signs to look out for (16,17).

Viruses (eg enterovirus, norovirus and hepatitis A)

Norovirus typically presents with the usually unpleasant gastrointestinal symptoms – nausea, stomach discomfort and diarrhoea. Projectile vomiting is often a telltale sign of norovirus (18).

Enterovirus produces flu-like symptoms: runny nose, aches, sore throat, vomiting and nausea. It can, however, produce more severe symptoms like breathing difficulties (resulting in blue lips and chest pain) and can lead to other illnesses such as viral meningitis and heart problems (namely, pericarditis and myocarditis).

Initial hepatitis A symptoms tend to be relatively mild – slight fever, joint pain, abdominal discomfort – but more severe symptoms like yellowing of the skin and eyes, dark urine, pale stools and itchy skin can appear as the virus begins to affect the liver. Hepatitis A usually passes in a couple of months, however be aware that in rare cases it can lead to liver failure (19).

Lead poisoning

Lead poisoning can be extremely dangerous as it directly impacts the brain. Symptoms include high blood pressure, headaches, fatigue and memory loss. It can also lead to miscarriage or premature birth in pregnant women (20). Natural sources of water can be contaminated by lead so if you spot any of these symptoms after a hiking trip consult your doctor.

Water hemlock poisoning

Water hemlock is, according to the Agricultural Research Service,” the most violently toxic plant that grows in North America.” It can cause death in “as little as 15 minutes” (21), even when consumed in small amounts, with symptoms ranging from drooling, nausea and vomiting to convulsions, heart problems, kidney failure and death.

Your best defence against poisoning by water hemlock is to identify it (check out this wikihow to learn how to spot it) and avoid drinking water from sources near the plants.

Water Intoxication

Since much of this article has emphasised the importance of drinking plenty of water it’s important to point out that you can also drink too much water. Symptoms of water poisoning include “nausea, vomiting and headaches and in serious cases, brain swelling, confusion, seizures, coma and death” (22). Drink plenty of water but don’t go crazy – too much water can lower your salt levels and cause life-threatening difficulties.

Frequently Asked Questions

– Can water poisoning kill you?

Drinking too much water can kill you by lowering salt levels in the body.

– Can dogs get water poisoning?

Dogs can also get water poisoning by drinking too much water (23)

– How long should you boil water for drinking?

This depends on a number of factors such as the clearness of the water and the elevation at which you’re boiling it. Clear water at a height of less than 6,500 metres should be safe after one minute, but since being safe is better than being sorry boiling for over ten minutes would be a better bet (24), (25)

– Why should you not drink salt water?

There is so much salt in saltwater that the kidneys have to increase urination to try and purge it from the body. As a consequence it forces us to expel more water than we consume and leads to dehydration (26)

– Will a magnifying glass purify water?

Theoretically a magnifying glass could focus the sun on water and boil it for purification purposes (apparently this has been done). Practically, the size of lens required makes this a no go on the trail.

– Will alcohol purify water?

No. Alcohol is a natural disinfectant but would be too diluted by the water to kill pathogens .

– Can silver purify water?

Silver does have antibacterial properties. Research suggests that silver can reduce pathogens in water to safe levels but it is not yet an established method of water purification (27)

Note: I’m not a doctor and this article should not be used as medical advice. 

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