Water Purification For Travel: What Smart Travelers Need to Know

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water bucket and spring in rural Vietnam
Water source in rural Vietnam

“Don’t drink the water” is a classic warning to travelers. But how much do you really know about water purification for travel?

If the locals drink the water, is it safe for you to risk it?

If your trip is long enough, is it worth it?

Is getting it wrong “just” a matter of spending a few days crouched in a pit toilet, or could you potentially catch something deadly?

What’s the difference between a filter and a purifier?

And which of the zillions of available water filters and purifiers are most worthy of valuable space in your luggage?

Those of us living in countries like the United States, where tap water is regularly inspected and safe to drink, are extremely fortunate. Hundreds of millions of people around the world lack access to safe drinking water, which is a leading cause of death especially in children.

As travelers, we have the privilege of avoiding most of these issues with a little preparation and knowledge. While I’m all for exchange of culture and perspectives when I travel, exchange of parasites and harmful bacteria is something I try to avoid.

Locals fetching water in rural Tanzania

In this guide I’ll lay out everything you need to know about safe drinking water during travel, based on research and my own travel to dozens of countries. We’ll cover these topics:

  • Types of waterborne illnesses – what are we even worried about?
  • How to know where it’s safe to drink the water
  • The important difference between filtration and purification
  • Tradeoffs of purification versus bottled water
  • Available water purification methods for travelers
  • Which purification method should you choose?

Types of Waterborne Illnesses

Before we get into the practical part, let’s quickly review the nasty little buggers we’re dealing with. This will be important later so we can understand how to choose a purification method.

Shore of the Mekong River in Vietnam

There are three main categories of waterborne pathogens:

Bacteria

Bacteria, especially E. Coli, are the most common cause of water-related illnesses in travelers. Traveler’s diarrhea, Montezuma’s Revenge, Delhi Belly… Been there, done that, let’s not do it again!

Other examples of bacterial infections caused by contaminated drinking water include typhoid, cholera, salmonella, and campylobacters.

Bacteria are probably the easiest category for travelers to deal with. Their relatively large size means that most filters are sufficient, and chemical treatments like iodine and chlorine wipe them out reliably.

Parasites / Cysts / Protozoa

These nasty little critters can be as small as one cell. Common waterborne parasites include Giardia and Cryptosporidium. They are relatively large (microscopically speaking), making them easy for common water filters to catch.

Cryptosporidium is a bit more problematic. Its hard shell resists chlorine and iodine, and takes several hours to break down even with chlorine dioxide treatment.

Giardia parasite – www.mantis.cz/mikrofotografie

Viruses

These are the tricky ones, and the biggest difference between water filtration for backcountry travel in developed countries (think hiking in the Sierra Nevada mountains) versus travel in developing countries.

Viruses are too small (0.02 – 0.3 microns) to be caught by water filters alone, so an additional purification method – like chemical or UV treatment – is needed in order to inactivate (“kill”) them. They can also be quite nasty diseases, including Hepatitis A, Hepatitis E, Polio, and Norovirus.

Down below I’ll talk more about how to make sure your water purification method protects against viruses.

Hepatitis A – Electron Micrograph Electron micrograph of Hepatitis A virus. 1976 Betty Partin tray #2, B77-764

Where is the water unsafe to drink?

I hate generalizations in general 🙂 but I’m going to make one here: broadly speaking, the less “developed” a country is, the more carefully you should avoid drinking the tap water, or water from natural sources such as rivers, lakes and wells.

This is partly because places with less robust infrastructure aren’t able to create and maintain the large-scale systems needed to provide clean water at a country-wide scale. It also has to do with the more vicious microorganisms that thrive in equatorial climates, which (probably not coincidentally) tend to be correlated with lower development levels. And, in places without good sanitation infrastructure, diseases easily make their way into water supplies via human waste.

Drinking water at a school in rural Guinea

The best strategy for your trip is to search for details on the specific countries you’ll be visiting. To give you a rough idea, here’s how I personally think about the risk level of drinking water when I travel. This is my own system, not an official recommendation, so be sure to do your own research.

Level 1: Safe to Drink

In these countries you can expect to drink water directly from the tap with no adverse effects, even if you’re not from the area. Do note that this doesn’t always apply to natural sources like rivers or lakes, which may carry contaminants from humans or animals and need to be filtered.

Examples: United States, Canada, Singapore, Hong Kong, Japan, South Korea, Israel, New Zealand, Australia, Finland, Ireland, Spain, many other European countries.

Level 2: Potentially Unpleasant to Drink

This is the middle category of places where the water is unlikely to seriously harm you, but it very well might ruin your trip. The locals might drink it, but the unfamiliar microorganisms can land visitors in the toilet for a few days with a bad case of traveler’s diarrhea. Water quality might be unevenly distributed in these countries; it might be considered safe in the major cities, but not in rural villages.

A few hardy travelers, especially those staying for months or more, might decide to drink tap water in cities if the locals do. The hope is that a bout of illness is worthwhile if it leads to resistance and the convenience of drinking untreated water during a longer trip. Those on short trips, however, will probably want to drink treated or bottled water to avoid an unpleasant disruption to their itinerary.

People who are at higher risk for complications from illness – young, old, pregnant, immune-compromised – should still be very cautious about water purification in these countries.

In these types of countries I will usually drink treated or bottled water only, but brush my teeth with tap water, being careful not to swallow any. I may drink tap water in cities where it’s widely agreed to be safe.

Examples: Chile, Argentina, Bulgaria, Albania, Hungary, many others

On Chile’s Carretera Austral I would drink tap water in the cities, and filter water from natural sources and the tap in small villages.

Level 3: Dangerous to Drink

In these countries the local water sources can carry some seriously nasty, potentially deadly bugs: Hepatitis A, Typhoid, Polio, Guinea Worm Disease… These risks go above and beyond a bad case of traveler’s diarrhea.

Travelers in these countries should absolutely not drink the local water without purifying it. Even if the locals do (those who have the means will purify it, but some may not have the knowledge or equipment). Even if you’re going to be staying for a while.

My personal rule of thumb is that I even brush my teeth with bottled or treated water in these countries. I also try to keep my mouth closed while showering or washing my face.

Examples: Uganda, Ethiopia, Ghana, Nigeria, much of the rest of Africa, Nepal, India, Cambodia, many others

Waterside slum in Monrovia, Liberia
Highly contaminated water in Monrovia, Liberia

What about…?

Brushing my teeth?

As mentioned above, I’m more relaxed about teeth brushing. For countries I consider to be level 1 or 2 based on my research, I’ll brush my teeth with tap water, being careful not to swallow any in level 2 cases.

In level 3 countries where dangerous viruses are a serious concern, I won’t risk it. In these places I only brush with treated or bottled water, and try not to get water in my mouth when showering or washing.

Water in restaurants?

This depends on the restaurant. In touristy places it’s usually assumed restaurants will serve bottled water. In more locals’ areas you may want to ask. In high risk areas you might want to not risk it at all, choosing to bring or purify your own water.

Ice in drinks?

This also depends. In much of Southeast Asia, for example, I found that ice was made from bottled water. In West Africa I was not always so sure. In touristy areas it’s highly likely to be safe, but you can always ask.

Purification Versus Bottled Water

Travelers have long been advised to drink bottled water in countries where the tap water isn’t reliably safe. However, with increasing focus on environmental concerns (where is all that plastic going?) plus plenty of affordable and compact treatment options, there’s no reason to rely on bottled water any longer.

If saving the planet isn’t enough motivation for you, consider that treating your own water is convenient or even essential if:

  • You plan to do any hiking or backcountry travel and need to drink from natural sources.
  • You’ll be spending time in small villages where bottled water may not be readily available.
  • You realize at midnight in your hotel that you’re out of bottled water and the nearest store is either closed or very far away.

Finally, if you travel often or to places with higher costs, treating your own water will save you money. Purifiers are relatively cheap, and the costs of bottled water can really add up.

Floating market in the Mekong Delta of Vietnam

Purifiers Versus Filters

You might hear the terms “water filter” and “water purifier” and assume they’re interchangeable, but there’s actually a critically important difference: virus protection.

Water filters remove the bad stuff by catching it in pores that are too small for it to fit through. As mentioned above, this works great for parasites and most bacteria, but not for the tiny little viruses.

To get the viruses, you need a purifier. Purifiers use an additional method, such as chemical or UV treatment, to kill viruses that would flow right through a filter and into your water bottle.

In summary, for international travel to what I called “level 2” and “level 3” countries above, you want to purify, not just filter, your drinking water.

A word of caution: I’m noticing lately that some products on Amazon use “water purification” or “purifier” in their titles, when they are actually only filters. Presumably this is to optimize for searches from people who think purifying and filtering are the same. This one, for example, is ambiguous. They claim 0.01 micron filter size, which in theory is small enough to catch viruses, but they don’t claim virus protection. Personally I would avoid relying on ambiguous products like this when traveling in developing countries.

Water Purification Methods for Travel

There are a number of ways to purify drinking water. I’ll go through the main ones here briefly, and then explain how you should choose between them. Except where otherwise noted, all these methods are effective against all three forms of waterborne diseases: bacteria, parasites, and viruses.

Chlorine Dioxide

This simple chemical treatment is small and light, and easy to use: just squirt a few drops or drop a tablet into your water. It’s easy to scale up to treat larger quantities.

However, you need to wait 30 minutes for it to work on most contaminants, and 4 hours for Cryptosporidium (though the wait time is the same for small and large quantities of water). It’s great for short trips, but you may not want to carry enough to use regularly on longer trips.

I find chlorine dioxide drops to be ideal for short and lightweight trips, and as a backup to another method on longer trips. I like to use them with two large (1.5 liter) bottles, so I can drink from one while waiting for the other to be treated.

Pump Purifier

Pump purifiers use a combination of filter and chemical treatment to purify water. They’re very reliable and simple to use for treating large quantities, but the time spent pumping can be a pain if used frequently. They’re also bigger and heavier than most other methods.

Most purifier elements need to be periodically backflushed or cleaned, will eventually need to be replaced, and can be damaged by hard impacts or freezing temperatures.

Gravity, Squeeze, or Inline Purifier

Similar to pump purifiers, gravity purifiers use gravity to push water through the purification element instead of pumping. This makes them less labor-intensive, but gravity purifiers can be slow.

Cartridges used in gravity purifiers can also sometimes be set up as squeeze purifiers, where you push the water through by squeezing the dirty water container, or inline purifiers, where you suck the water through as you drink it.

Most purifier elements need to be periodically backflushed or cleaned, will eventually need to be replaced, and can be damaged by hard impacts or freezing temperatures.

Ultraviolet (UV) Treatment

UV treatment devices like the SteriPen treat water quickly and easily by submerging the device, pressing a button, and waiting a short amount of time.

However, as electronic devices they are vulnerable to issues like dead battery or bulb failure. They also don’t work in cloudy water. Treating large quantities can be awkward since a single treatment only purifies one bottle’s worth of water.

Bottle Purifier

Bottle purifiers use various methods (UV, chemical, and/or filtration) to purify your water right in the bottle you drink from. This makes them very convenient for certain usage patterns (filling up a single bottle to go sightseeing for a day), but awkward for other cases (treating several liters at a time for camping or long days out).

Note that many bottle filtration products are only filters, not purifiers, and don’t protect against viruses. Be sure to check the fine print.

Boiling

If you have easy access to a stove and plenty of fuel (a kitchen, or a camp stove), this is the simplest method. Bring the water to a rolling boil for 1 minute (3 minutes if above 6500 feet elevation) and it’s good to go.

The obvious drawback: the water will be very hot until given time to cool. It also doesn’t remove unharmful but gross gunk like silt and algae, which can be an issue when drinking from natural sources.

Unsuitable Water Treatment Methods for Travel

Chlorine and Iodine – NOT usually suitable alone

Unlike chlorine dioxide, these classic water treatment methods don’t kill Cryptosporidium. Some people also don’t like the taste, or feel it’s unhealthy to use them regularly for long periods of time. Use chlorine dioxide instead.

Filters – NOT usually suitable alone

Any product marketed as a “filter” is most likely not a purifier, which means it won’t protect against viruses. When traveling in developing countries where viruses are a risk, a filter alone is not enough. Beware especially of bottle filters and straw filters, which can often be marketed to travelers despite their lack of virus protection.

Note that some filters are marketed as “two stage” but even this doesn’t guarantee virus protection: the second stage may be a carbon filter that simply improves the taste.

You can, however, use a filter plus a chemical treatment for complete purification. The filter will take care of bacteria and parasites, and the chemical treatment will take care of viruses. I like the flexible and lightweight Sawyer Mini for this purpose.

Which type of water purification is best for travel?

That’s a lot of options! How on earth are you supposed to choose?

Of course personal preference comes into play, but over the years I’ve found that the best water purifier depends on the type of trip. Here are my recommendations for a few specific scenarios:

  • Short trip with lightweight luggage, or a trip where you’ll only occasionally need to treat your water: chlorine dioxide drops or tabs, because they are so small and lightweight. Just be sure to plan ahead so the drops have time to work before you need your water.
  • Long trip with daily water treatment needs: gravity purifier and/or chlorine dioxide tabs. Both are easy to use for large quantities of water, as long as you have time to wait.
  • Trip including camping, hiking, or otherwise getting water from natural sources like rivers or lakes: gravity or pump purifier, or microfilter plus chlorine dioxide combination. Both of these will safely handle cloudy or silty water. Personally I lean away from the pump since I hate pumping water, but if you’re traveling with others and can trade off pumping duty, it’s not so bad.

I’ve glossed over UV and pump purifiers in these recommendations, mainly because it’s been awhile since I’ve used them. I’m satisfied with my other methods and haven’t felt a need. But I realize many people love them. If you’re one of them, tell us about it in the comments below. I would love to update this guide with more detailed recommendations about when these methods really shine.

I also haven’t recommend bottle purifiers, despite their popularity, because my travel is typically rugged, includes outdoor activities and drinking from natural sources, and requires that I treat large quantities at once. But for tourists visiting mainly urban areas and looking for a convenient way to treat small quantities on the go, bottle purifiers might be great.

Best Water Bottles and Containers for International Travel

Once you purify your water, you’ll need somewhere to put it. You can certainly buy a disposable plastic bottle (the large 1.5 liter ones are available pretty much everywhere) and refill it. But I always bring my own reusable water bottles when I travel. Here are a few of my favorite picks for more unique and rugged travel situations:

Fold-able 1 liter Platypus bottle: These are my go-to for airplane travel. They fold down to nothing when empty, are easily filled in the airport after passing through security, and fit nicely in the airplane seat pocket. They’re also great once you’re at your destination, simply because they don’t take up any space when empty.

Nathan SuperShot 1.5 liter bottles: these things are huge! Any water bottle you use in the future will seem too small by comparison. For long journeys or the convenience of treating larger amounts of water at once, 1.5 liters is a great size. I use them on my bicycle when bike touring and they are basically indestructible.

Platypus 3 liter hydration bladder: For outdoorsy travelers, this is indispensable. It holds plenty of water for most long days of hiking or biking, a night of camping, or even just a convenient source of purified water while hanging out at a hostel or guesthouse. Treating 3 liters at once is convenient, and they take up almost no space when empty.

More Travel Resources

If you’re heading off on adventures abroad, you might also find these helpful:

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Pictures of bucket and fountain with text: guide to safe drinking water for travelers
Pictures of water filters and purifiers with text: The best water purifiers for travelers

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