Travel tips: Water purification for travel and expeditions


Everyone knows that when overseas, tap water can be unsuitable for drinking, and could cause illness. There is also generally good awareness that water used for brushing teeth should also be from a safe source, and to avoid things such as ice in soft drinks which may be made from contaminated water. In this article on water purification for travel and expeditions, I’ll detail my four preferred methods of providing safe drinking water for yourself.

So, what makes you ill?

There are three types of waterborne microbes which can cause illness; Bacteria (such as E.Coli, Salmonella, Cholera), Viruses (like Hepatitis) and Protozoa, also known as cysts, (such as Giardia).


Isn’t bottled water the solution?

When travelling the most common advice is to buy bottled water, and double check the seal on the bottle is unbroken before consuming. However, much bigger than the financial cost of buying water, is the environmental cost.

Not only does the transportation of heavy and bulky bottles of water have a considerable carbon footprint but it also produces rubbish in the form of plastic bottles which, in countries already struggling to manage waste, only contributes to the problem.

When on multi-day trekking trips and expeditions bottled water is not an option and various methods to purify water are used to provide clean water. I now use these methods not only on expeditions but whenever I travel.

Below is a summary of my four preferred methods which I use to treat water on my travels. I discuss the pros and cons of each system. It’s not an exhaustive list of all the water purification options and on any trip I may use several of these methods.



Boiling water is the most widely used way to kill all waterborne microbes. When camping a stove used for cooking can also be used to boil water. Outdoor enthusiasts often talk about letting the water boil as a ‘rolling boil’ for 2 minutes. Actually, even the nastiest microbes are killed at 60ºC, it’s just it’s hard to tell when water reaches 60ºC. So, to be on the safe side, let the water come to a proper boil, so that large bubbles are rolling over each other, but I’ve never seen the need to do this for 2 minutes.

Using boiling as a method to treat water is great news for tea and coffee drinkers, but if you’re not a fan try herbal teas, hot water and lemon, hot chocolate and hot squash as other options.


  • Kills all bacteria
  • When camping a stove is usually carried which can be used to boil water
  • In most places and cultures it’s possible to order a hot drink, and in self-catering or hostel accommodation, there is access to a stove or kettle.


  • It’s not always convenient to boil water.
  • Fuel for a camping stove is both heavy, bulky and costly. You might not want to use it to purify all your water.
  • If you don’t want a hot drink, cooled water often tastes strange, and takes a considerable time to cool.

SteriPEN Freedom

SteriPen Freedom

SteriPEN products are neat little gadgets which use UV light to alter the DNA of microbes, making them unable to cause illness. It’s not new technology, many households on a private water supply in the UK use this, it’s just that SteriPEN have made it hand-held.

SteriPEN have several different designs of essentially the same product but I like the rechargeable SteriPEN Freedom which comes with a solar panel. Depending on the trip I may or may not take the solar panel. If I do want to recharge via solar I often use a separate, more versatile, solar panel I have, rather than the one the SteriPEN comes with. I can also charge the SteriPEN Freedom from the mains via a USB cable and plug. On short trips, charging before I go is all I need.

To use the SteriPEN Freedom immerse the UV bulb fully into the water. It automatically turns on. Stir until the red light turns to green after 48 seconds or so, for a ½ litre, and then it’s done.

After using this system on several trips I have found that it works best shared between no more than four people, with bigger groups it feels like it takes forever to get everyone’s water purified and also requires charging frequently (every couple of days).


  • No bad taste.
  • No chemicals used.
  • Can easily sterilise small quantities of water such as one glass.
  • Good for long-term travel as, if charged, can purify 20 litres per charge (although in testing I found it to sometimes be less) and 4,000 litres of water for the life time of the lamp.
  • If the lamp comes to the end of its life span SteriPEN will replace your SteriPEN for free.
  • Can’t ‘over’ treat.


  • Can’t purify bottles larger than 1 litre.
  • Requires the battery to be sufficiently charged.
  • The Freedom is designed to work with ½ litre bottles. A double treatment (i.e. double the time) is required for 1 litre bottles.
  • Although it treats water the fastest for the all the methods here it does require 50 seconds of stirring (~1 min 30 seconds for 1 litre). This doesn’t sound like long but putting a couple of drops or tablets in the water and leaving it for a bit is easier.
  • Can be tedious waiting for water to be purified, especially if doing several 1 litre bottles at a time.
  • It is possible to break the lamp (it’s made of glass) or for the SteriPEN to malfunction in other ways.
  • Bacteria can ‘re-activate’ if water is exposed to sunlight.
  • A bottle with a wide enough neck for the filament to fit in is required (the Freedom comes with a bottle). A standard plastic water bottle has too narrow a neck.
  • The light on the Freedom is hard to see in bright sunlight so difficult to work out when the treatment is done.

Chlorine or Chlorine Dioxide tablets

chlorine tablets

People are often resistant to adding a chemical to water in order to make it drinkable, forgetting that most drinking water in the UK has fluoride and chlorine in it, so if you drink tap water in the UK you are regularly drinking water with a chemical in it.

Chlorine and chlorine dioxide is extremely safe and I am not worried about drinking water purified by it. Both can be bought in tablet form which are compact and lightweight. In fact, I always carry a packet of ten tablets in my first aid kit so I know that I always have some on me. One tablet generally treats 1 litre of water and you must wait 10 minutes for the tablet to take effect.

Chlorine is less effective than chlorine dioxide, not being able to treat protazoa like Giardia, it also has the disadvantage that it can can leave the treated water tasting a little like a ‘swimming pool’. However, it is cheaper.

Most people get used to the taste of chlorine but some people really dislike it and it can discourage people, especially younger people, from rehydrating properly. I find a few things help. It is possible to buy neutralising tablets which remove the taste. Using cordials or flavoured drinks powders can mask the taste. Also, leaving the treated water to stand with the lid off allows the chlorine to evaporate off once it has done its work.


  • Can be added to any shaped bottle or water container.
  • Can be made up into a stronger solution for treating particularly suspect water or for washing fruit and veg.
  • Very lightweight to carry in small quantities.
  • Impossible to break or spill, unlike a SteriPEN or Aquaprove.


  • Can’t easily purify less than a litre of water, but can purify much larger quantities.
  • Need to wait 10 minutes until the water can be drunk.
  • Need to estimate how many tablets you need for any trip and buy in advance.
  • Some people don’t like the taste, which could result in them not rehydrating properly.
  • Cold water takes longer to purify.
  • Chlorine has a limited effectiveness against protozoa such as Giardia. Chlorine Dioxide, however, does kill protozoa including Giardia which is a major advantage and worth the extra money.

Aquaprove (Chlorine Dioxide solution)

Aqua prove

Aquaprove is one of my new favourite ways to sterilise water. This simple system uses the advantages of a Chlorine Dioxide treatment but is faster acting than tablets and has the ability to purify small quantities whilst not having a chlorine taste.

The treatment is bought as a tablet with a small plastic bottle. When you need to treat drinking water simply take the tablet out of its packaging, put it in the 50ml bottle, add tap water and wait for 10 minutes. Now the Aquaprove is in a concentrate Chlorine Dioxide solution form and can be used to treat water.

The concentrated solution can be added to the water requiring treatment taking just 5 minutes to work. Four drops purifies 1 litre which means that it is easy to purify smaller quantities, such as a single glass of water. Each bottle can treat up to 250 litres of water.

Once the solution has been made up by dissolving the tablet in the bottle it is only effective for 40 days, hence why you only make it up when you need it, rather than it being purchased as a solution. I recommend writing a date on the bottle in permanent pen recording when you make it into a solution to keep track of this.


  • The quickest method of chemical treatment.
  • Can be added to any amount of water from ¼ litre up.
  • Lack of chlorine taste.
  • Comes in a compact and convenient plastic bottle, so difficult to break.
  • Can be used in any shaped bottle or water container.
  • Can make up stronger solutions for washing fruit and veg.
  • Less fiddly than opening tablets.
  • One small bottle can treat up to 250 litres of water.


  • The solution goes out of date 40 days after being made into a solution from its tablet form.
  • Currently, it is only possible to buy in packs of 10 or larger.
  • Can be spilt.
  • Can’t just take the ability to treat 10 litres, for example, which means tablets might be more suitable for short trips or to carry just in case.


On any trip I’ll use at least two of these methods, often three. It’s not a set formula, instead, about picking the methods suitable for your trip.



With all these methods of treating water it is important that the source of the water is free form particles and chemical contamination. Although, having particles in the water are not necessarily harmful in themselves, they do make any purification method less effective.

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