Drinking clear, fresh water that appears fit for consumption "from its source" - is it a good idea? Not really. So, to avoid unpleasant surprises, here is how to filter and purify your water during a hike to make it drinkable.
Every day, our body loses on average 2L of water (sweat, urine, etc.), but this consumption increases if you practise physical activity outdoors, in hot or cold weather. Even if you go on a trek with a water supply, the thing about supplies is that, after a while, they run out. So, you have to stock up again!
Where to collect water? How to make dirty water clear? What are the different filtration systems? Which technique is the most effective? We’ll answer all your questions.
Drinking water is simply water that’s safe to consume. Drinking water standards vary depending on the country. To date, in France, there are 63 potability criteria. We don't need to tell you all of them.
Drinking water is not necessarily free of all pollutants. These can be present in very small quantities and regulated by standards.
Staying hydrated when hiking is essential. The water you encounter along your way (lakes, rivers, wells, etc.) may not be drinkable because it’s contaminated by different types of chemical and organic pollutants.
Chemical contaminants are due to human activity and urbanisation (pesticides, hydrocarbons, nitrates, etc.).
Organic pollutants are natural organisms that grow in water. Even if the majority are harmless, some can cause us problems! These organic pollutants are classified into 3 categories: parasites (tapeworms, amoebas, etc.), bacteria (Escherichia coli, staphylococci, salmonella, etc.) and viruses (hepatitis, etc.).
An initial question arises: where to collect water during a hike or trek? Choose a fresh water source that’s as far away from human activities as possible. For example, avoid water sources downstream from a home or farm. If you can, choose your water point as high as possible and avoid stagnant water.
The water collected should be as clear as possible, but depending on where you are, that isn’t always possible. Deposits, solid particles... The water can be cloudy, even muddy. This is called turbid water. In this case, your first mission is to transform this cloudy water into clear water. This is the pre-filtration stage. The aim? Eliminate larger particles and optimise the efficiency of your filtration technique.
For this, you can opt for the sedimentation technique. Decant your water in a container for 1 to 2 hours, and the heaviest mineral particles will fall to the bottom. Then gently pour the water into another container and leave the particles in the first container. The latter is contaminated, and so must not be used! It may therefore be useful to provide a container solely for this type of use.
If the water collected still isn’t clear and there are deposits remaining, is it because decanting isn’t sufficient? You should then filter the water.
To filter your turbid water and make it clear, you can use a coffee filter, but if you don't have one to hand, a piece of mosquito net or simple piece of fabric (a T-shirt, for example) will do a pretty good job.
There are several techniques such as boiling, chemical treatment, filtration or treatment with ultraviolet radiation.
Boiling is certainly the oldest solution used by hikers to purify water!
Boiling isn’t effective on dirty (turbid) water, so you must first filter the water or collect clear water.
The boiling point varies with altitude. For example, at sea level, it’s 100°C, while 2000m up, it’s 93°C. A quick general knowledge moment - at the summit of Everest, the boiling point is 72°C.
How long should you boil your drink for? Again, this depends on your altitude. 1 minute is enough when the water boils at 100°, but several minutes are required as you gain altitude.
The biggest advantage of this technique? Its efficiency! In fact, boiling eliminates all kinds of organic pollution.
This technique still presents certain constraints, such as boiling time, the equipment required (need for fuel), and waiting time before your water cools. Note that this technique isn’t effective on chemical pollutants.
The advantages of this technique? Chemical purifiers are lightweight, small and very easy to use.
Simply place a tablet or pour a few drops of a treatment based on iodine and chlorine into your bottle filled with fresh water and wait for it to take effect (from 30 minutes to a few hours, depending on the brand). The water must first have been filtered to guarantee the effectiveness of the treatment. Note that the colder the water, the longer the treatment takes.
Thanks to the chemical reaction, this chemical treatment effectively eliminates all viruses and bacteria, but some parasites are still resistant to these methods (although most are eliminated within a few hours). Note that this technique isn’t effective on chemical pollutants.
Disadvantages? Well, yes, there are a few. Once treated, the water can have a fairly chemical taste which may put some people off. The tablets always have an expiry date (check carefully in advance!), and if used repeatedly, they can damage the intestinal flora.
There are various treatment devices such as the filter straw, the flexible or rigid filter bottle, the filter on a water bag or even a pump on the hydration system. How to choose ? Depending on the volume of water you want to filter, as well as your storage constraints and weight and size.
How does fresh water treatment by filtration work? The water passes through the filter with tiny holes in it that block contaminants. This filtration technique is often supplemented by treatment with activated carbon (which removes the unpleasant taste).
There are two types of mattresses: microfiltration and hyperfiltration. The difference lies in the pore size of the filter and therefore the type of contaminant it filters. Microfiltration (0.2 micron filter) is effective on bacteria and parasites, but not on viruses, which pass through the filter. Hyperfiltration, also called ultrafiltration, is effective on all organic contaminants, viruses included, because its filter is 0.02 microns (therefore 10x smaller).
The advantage of filtration? Its speed! The water, once passed through the filter, is potable water suitable for consumption. This technique also lets you filter larger volumes of water and doesn’t give a particular taste to your drink.
Electronic UV treatment tools are usually shaped like a pen. Practical to carry, they are also very easy to use since you just need to dip the device in your hiking bottle or other container and wait for the magic to happen. In terms of time, the advantage of this technique is its speed, since approximately 1 minute 30 is enough to purify 1.5 L.
So how does it work? The UV purification system doesn’t remove contaminants such as viruses, bacteria and parasites, but immobilises them to render them harmless. This treatment based on ultraviolet rays is only effective on clear water. However, it’s ineffective on chemical pollutants.
Please note that this UV treatment works on batteries. The battery solution is therefore perhaps not the most highly recommended if you’re going on a trek for a few days.
Desalinating sea water to make it drinkable is a very expensive solution that’s generally unsuitable for hikers and backpackers. Techniques for transforming salt water into drinking water are very energy-intensive and often developed on an industrial scale. So even though sea water represents around 3/4 of our planet, it’s probably not the solution for providing water during your treks and travels.
As you may have realised, an ideal system that ticks all the boxes doesn’t exist. All these solutions have lots of advantages and some disadvantages. Choosing yours will depend on where you’re hiking (on certain continents, viruses are more active than others), how much space you have in your bag, as well as your habits during treks, hikes and trips.
💡 It’s also possible to combine techniques! For example, you can use a filtration system to eliminate bacteria and parasites and supplement it with a chemical tablet to eliminate viruses.
So several techniques exist to filter and treat water during your hikes or touring treks. One thing to keep in mind? Avoid drinking directly from the source to avoid health mishaps linked to the consumption of non-drinkable water. It’s better to have some great hiking stories to tell. In addition, today, most filtration techniques are convenient to carry and fairly easy to use.
Passionate about dance, keen on fitness centres, lover of water and apprentice runner, when I'm not practising sport, I like to write about its history and benefits!
