How to purify water

Drinking water is vital. And especially during hiking, it is important to always stay sufficiently hydrated. But how do we guarantee on our adventures that the water we drink is safe? There are so many water purification systems on the market today that you can hardly see the forest for the trees anymore. But don’t panic. I made a handy list for you with the ten most important water purification techniques, so you never ever have to be thirsty on your hikes again. Cheers!


Why purify water?

Everyone knows that you can get sick of polluted water. But what exactly is it in that dirty water that makes us feel so bad?

We can divide the sick makers in water into three subgroups:

  • Viruses: Viruses propagate through living organisms. Virus infections can not be treated via antibiotics. Viruses can cause diarrhea, but also Hepatitis A and B.
  • Bacteria: There are bacteria that are never problematic. Some are even useful. But others can make people sick. Bacteria in contaminated water can cause cholera and typhoid fever.
  • Protozoa: Protozoa is a difficult word derived from the Greek “próta zóa” and could be translated as “primal animals”. They are single-cell micro-organisms that can cause a variety of bowel diseases.


What you definitely should not do!

Before we consider the various water purification methods and systems, it is important to mention what you should not do when you are thirsty:

  • Drinking urine: urine contains harmful substances and salt, which will make you even more thirsty.
  • Drinking blood: in addition to salt, blood can also contain possible diseases.
  • Drinking seawater: the high salt level in seawater will only make the dehydration worse.
  • Drinking alcohol: alcohol worsens dehydration, but it will also influence your judgment, which can be detrimental in a survival situation.


Water purification methods

Now we’ve got that out of the way, it’s time to explain the various water purification methods and systems. I listed ten of the most important systems and techniques for you.


1.      Boiling

The most obvious method to purify water is to simply boil it. The biggest advantage is that you do not have to take extra material (read: weight) with you, because a gas burner and pot are probably already in your backpack anyway.

Boiling water to purify it is pretty effective. By letting the water boil for five minutes while stirring, you can rest assured that all possible micro-organisms have died and can not make you sick anymore.

Cooking during our Mare a Mare Nord adventure on the isle of Corsica

Turbid water unfortunately remains cloudy. Therefore, you can consider filtering it first through a clean handkerchief or a clean piece of clothing such as a t-shirt or a sock.

A disadvantage of this method is that it is quite time-consuming. When you pass a river along the way, it takes a little effort to unpack your cooking utensils and boil the water. Moreover, you will have to be extra patient to let the water cool down, if you crave a delicious sip of fresh water.

Advantages Disadvantages
No extra weight Fuel or wood fire needed
Cheap Long cooling time
Very effective Turbid water remains cloudy
  Time consuming

Our adviced products:


2.      Saturated iodine solution

Iodine is a super powerful product. It puts a stop to viruses, bacteria and germs. Most parasites are also destroyed by iodine. The recipe is simple:

  • Mix 8g of iodine crystals with 30ml of water.
  • Shake well and leave for an hour.
  • Mix 15ml of this iodine solution (without the crystals, because they are harmful!) with 1 liter of water.
  • Shake again and leave for fifteen minutes.
  • Done!

Iodine crystals are not always easy to buy. Some outdoor sports shops sell them. Instead of crystals, you can also use iodine tincture or a 2% iodine solution. This is available at the pharmacy and is used for the disinfection of wounds. In this case, add 0.4mg of iodine solution to 1 liter of water to purify it.

However, since a few years it has become clear that some bacteria outwit the iodine solution. It is in particular the bacteria cryptosporidium that will not be chased away by a few drops of iodine. You will not die from this bacteria, but it can make you pretty sick.

Advantages Disadvantages
Cheap Ready-made iodine solution is not available
Very effective Iodine crystals are difficult to obtain
Little iodine needed to purify a large amount of water Iodine crystals themselves can not be consumed, as they are harmful to health
Little purification time (15 min) Prolonged use can be detrimental to the thyroid gland
  Harmful for pregnant women and people with a thyroid gland disorder
  Funny taste
  Turbid water remains cloudy
  Existence of iodene resistant bacteria


3.      Chlorine

Chlorine is a widely used means to purify water. It is slightly less effective than iodine because it does not harm parasites. Chlorine is used to clear water from viruses and bacteria.

It is available as a water disinfectant both in tablet form (see further: “water purification tablets”) and in liquid form in almost all outdoor sports shops.

The most sold liquid form actually is bleach. It is an ideal way to make doubtful drinking water from wells and sources bacteriologically safe. Bleach consists of a properly balanced chlorine solution. The active substance is sodium hypochlorite. By adding 1 drop to a glass of water (0.2 liters) and let the product do its work for 30 minutes it is safe to drink.

To be sure that the entire trinity of protozoa, bacteria and viruses is inactivated, it is advisable to use bleach in combination with a filter. The filter first deals with the protozoa and bacteria, after which the chlorine solution attacks any remaining viruses in the filtered water.

Another derivative of chlorine is chlorine dioxide. It is both in its chemical structure and in its behavior very different from elemental chlorine. Probably the most important quality of chlorine dioxide is its high water solubility, especially in cold water. As a water purifier the bottled version of Aqua Mira is probably the most famous one in the outdoor world.

Because chlorine is volatile, the taste will largely evaporate if you leave the water for a while. But there are also tablets on the market that can easily extract the taste.

Advantages Disadvantages
Light-weight Funny taste
Easy to use Prolonged use can be detrimental to the thyroid gland
  Long purification time (30 min)
  Liquid chlorine has a limited shelf life
  Chlorine causes metal objects to rust
  Recommended to use in combination with a filter

Our adviced products:


4.      Silver ions

It is not all gold that glitters. It is perhaps therefore that silver is most effective when it comes to purifying water. Even the ancient Greeks and Romans knew this already centuries ago, since they used silver jugs for storing water and milk.

There are several heavy metals that have an inhibiting effect on bacteria, but it is in particular silver that has the strongest antimicrobial effect. The silver ions disrupt the functioning of enzymes, causing the processes in the cells to malfunction so they will eventually die.

One of the most important advantages of silver ions is that they stay in the water for a long time. Water that has been purified in this way remains drinkable for up to six months and is even protected against re-contamination. Treatment with silver ions keeps the water free from bacteria, algae and odors for a long time.

The killing rate of silver ions is not as high as that of ozone or UV. But the effect is better, because it is not only locally effective, as it is the case with UV. Some micro-organisms can develop a resistance to silver ions.

Turbid water can weaken the effect of the silver ions. Therefore, in case of turbid water, it is recommended to combine the silver ion treatment with a microfilter.

Advantages Disadvantages
Light-weight Some micro-organisms can develop a resistance to silver ions
Easy to use Long purification time (2 hours)
No funny taste Not usable in turbid water
Long term desinfection (6 months)  

Our adviced products:


5.      Water purification tablets

With the production of water purification tablets, the purifying effect of chlorine has been combined with that of silver ions. It seems that with these water purification tablets a real “winning team” has been created, in which the advantages of both purification methods are combined in one small pill.

With one tablet you can purify a liter of water. It is important to shake well so that optimal effectiveness can be guaranteed. The purification time takes half an hour. In case of very cold water, it is advisable to take into account two hours of purification time.

Advantages Disadvantages
Light-weight Funny taste
Easy to use Does not remove chemicals
Long term desinfection (6 months) Prolonged use can be detrimental to the thyroid gland
  Long purification time (30 min)
  Not usable in turbid water
  Does not extract bad smells and / or flavors from the water

Our adviced products:


6.      UV radiation

If you purify water by means of UV radiation, you are actually pasteurizing it. Thanks to the UV radiation, you are going to confuse the DNA of the micro-organisms in such a way that they are no longer harmful to your health. During this pasteurization process, not all microorganisms are killed, but they are brought back to a safe level. No less than 99.9% of all bacteria, viruses and protozoa are crushed by the UV radiation.

Photo by Katadyn

Filtering with a Steripen is very simple:

  • Place the Steripen lamp in your water bottle and activate the appliance.
  • Stir through the water until the lamp goes out.
  • Done!

The lamp goes out automatically when all harmful substances in the water are gone. When the red LED light changes to green, you know that the water is safe to drink.

It is recommended to pre-filter the water. Especially when the water is cloudy, the UV rays have a lot more trouble to get to the micro-organisms. The Steripen is therefore sold together with a pre-filter.

Advantages Disadvantages
Easy to use Expensive
Usable in practically any type of bottle Operates with batteries
LED light indicator shows if water is safe for consumption Pre-filtering is recommended

Our adviced products:


7.      Portable water filter pump system

There are three types of water filters with a pump systems :

  • Ceramic filter or glass fiber filter: The microfiltration system removes big and small particles from the water, including bacteria and some viruses. This type of filter is mainly used in standing water or in flowing surface water.
  • Filter with silver ions: This type of filter has a strong antimicrobial effect. But besides the destruction of bacteria, this filter also ensures a long shelf life of the water due to the presence of silver ions (see above: “silver ions”).
  • Activated carbon filter: The active carbon in this type of water filter removes any chemical contamination via industry or agriculture from the drinking water. 
Photo by Katadyn
Advantages Disadvantages
Clears turbid water Expensive
Effortless filtering of large amounts of water Heavy weight
  Regular cleaning of filter system needed

Our adviced products:


8.      Water bottle with filter

There are water filter systems that are directly attached to your water bottle. This specific design is also what makes this system so powerful. You have to take a water bottle with you on your trip anyway. Why not immediately choose a bottle in which a filter is integrated? You simply fill the bottle with the contaminated water and suck the purified water through the mouthpiece. Easy as 123.

In addition, it is also very effective: 99.9% of all bacteria and protozoa do not stand a chance against this water filter. Although the filter does not fit all bottles, it is designed in such a way that it is suitable for the most common models. It also fits a water bag system. That at least is true for the filter from the brand Sawyer. With the Katadyn BeFree filter you might have a bit more trouble finding a bottle that fits.

Photo by Sawyer

The amount of water that you can purify with this type of filter, you will not be able to drink in your entire life. In other words, this filter lasts a lifetime. In theory, that is. Because in reality some particles will get stuck in the filter after some time, as a result of which the volume of water to be sucked up will become smaller and smaller. Even after cleaning the filter, this problem remains.

But in fact, this type of water filter only has advantages: it is very light, the purified water has no aftertaste, the system is very easy to use, the filter can be easily cleaned and lasts (more or less) a lifetime. But perhaps the greatest advantage of this system is that you can drink the purified water immediately. No purification time or pump time required. Just fill your bottle up and drink.

Advantages Disadvantages
Clears turbid water Filter does not fit on all bottle types
No funny taste Not usable on rigid bottles
Light-weight Does not neutralize viruses
Easy to use Does not remove chemicals
No purification time  
Very durable  

Our adviced products:


9.      Mini water filters

The mini water filter can be considered the little brother of the water bottle with filter. The filter system that is integrated in this water bottle is also sold separately in the form of this mini water filter.

Photo by Sawyer

There are two ways you can use this mini water filter:

  • Fill up the included reusable pouch with contaminated water, screw the filter onto the pouch, and drink directly from the filter or squeeze the water into another container.
  • Screw the water filter onto a water bag or a bottle and drink the contaminated water directly through the filter.

Squeezing the water from the reusable pouch requires a little bit of force, but it works quite smoothly. When you choose the second option you have to take into account that this mini filter can only be used on bottles made of soft plastic, since you will produce a vacuum.

Advantages Disadvantages
Clears turbid water Filter does not fit on all bottle types
No funny taste Not usable on rigid bottles
Super light-weight Does not neutralize viruses
Easy to use Does not remove chemicals
No purification time  
Very durable  

Our adviced product


10.  Foam filters

A flexible silicone bottle in combination with an almost magical foam filter ensures that almost all contaminants are removed in fresh water, while improving the taste and smell at the same time. The system uses so-called absorption filtration, which means that the molecules attach to the surface of the foam membrane.

Sawyer produces these bottles in three models: the S1, S2 and S3. The S1 can be seen as the basic model and can be used 1600 times. The S2 can do everything the S1 can, but also neutralizes viruses from the water. It lasts up to 800 times. The S3 is the top of the bill. Besides viruses it also neutralizes heavy metals from the contaminated water. With the S3 you can drink safely up to 400 times.

Photo by Sawyer

The use of the foam filter bottles is simple. You can drink pure water in just a few steps:

  • Fill the bottle with contaminated water and screw the filter onto it.
  • Squeeze the silicone bottle in alternate movements for 10 seconds, so all the water is pushed through the foam filter.
  • Done!

You can drink directly from the bottle or pour the purified water into another container.

Advantages Disadvantages
Clears turbid water Only usable with the included bottle
No funny taste Relatively short lifespam of the S3 type
Easy to use Heavy weight
No purification time  
Neutralizes viruses (S2 and S3)  
Neutralizes chemicals (S3)  

Our adviced products:



In the table below we summarized all the advantages and disadvantages of every water purification technique.

*Used types in the table:

As you can see, there is more than just one efficient water purification system on the market. And they all have their own advantages and disadvantages. If you want to play it safe, you can choose to combine several techniques, although this will probably translate into extra backpack weight.

It should be clear that technology certainly does not stand still, when it comes to the evolution of water purification systems. With its recently developed foam filter, Sawyer has challenged its competitors in the water purification industry. Something that we can only encourage. We are already looking forward to the answer that the competition will undoubtedly give them in a very short term.

1 thought on “How to purify water”

  1. Pingback: The Red Sea Mountain Trail: Egypt's first long-distance hiking trail on the mainland - A Hiker's Tale

Leave a Comment

Your email address will not be published.