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Drinking Safe Water Abroad

Photo courtesy of GRAYL

Written by Travis Merrigan - GRAYL Co-Founder

Nothing ruins an international trip faster than getting sick with Travel Diarrhea (TD) - a.k.a, Montezuma’s Revenge, Delhi Belly, Rangoon Runs and other creative terms for something that is far from whimsical. TD is fairly common; 20-50% of travelers succumb, according to K. Leder from the Australian Family Physician publication. With this high level of risk, it goes without saying that taking precautions when eating and drinking abroad is pivotal to your health. This article is all about waterborne illness and how to avoid it when traveling.

What causes Traveler’s Diarrhea?

TD is almost always caused by ingesting contaminated food or drink. Water can be contaminated by three primary pathogens such as amoeba, tapeworms, algae and blood worms (oh my!). Other nasties can be found in water as well, including bacteria, protozoa, viruses and heavy metals.

  1. BacteriaE. coli, Dysentery, Leptospirosis, Typhoid, Salmonella and others

    1. The Good – Easiest pathogen to remove from water. Sickness generally lasts “only” a few days (a long and miserable few days)

    2. The Bad - Most common cause of TD – ruins more vacations than bad weather and mother-in-laws combined

    3. The Ugly – Left untreated, Dysentery and Typhoid Fever symptoms increase and can become fatal

  2. ProtozoaGiardia, Cryptosporidium, etc.

    1. The Good – Generally not fatal, weight loss guaranteed (don’t get any ideas)

    2. The Bad – Difficult to remove from drinking water

    3. The Ugly – In one study published in Arch INtern Med. (Ungar, et. Al, Serologic evidence of Cryptosporidium infection in US volunteers before and during Peace Corps service in Africa. 1989 Apr;149(4):894-7.), 33% of Peace Corps volunteers in Africa were afflicted by Cryptosporidiosis. Giardia is even more common.

  3. Virus – Norovirus, Rotavirus, Hepatitis A, SARS, etc.

    1. The Good – Probably the least common cause of TD. HepA is vaccine preventable.

    2. The Bad – Extremely difficult to remove from water

    3. The Ugly – Untreated, HepA, SARS and other viral infections are seriously no bueno

  4. Other bad stuff – blue-green algae, toxic chemicals, nuclear waste (National Water Quality Inventory: Report to Congress, 2004 (EPA 841-R-08-00))

    1. Too many potential risks to quantify. Don’t assume any filter will protect you against an industrial spill, mine disaster, very high lead levels or other water disasters

Dig Deeper:


Choosing Safe Water to Filter or Purify

Photo courtesy of GRAYL

Common sense dictates that when you look for water to filter, you look for the best source available to you. If you have access to clear water from a stream or muddy water from a pond, most of the time, you’d choose the clear water, right? Here are other tips for picking the best water source.

  • Rule of thumb: The further up the stream, the better.

  • If you can help it, don’t purify downstream from a town, village or factory - especially in developing countries. Towns and factories dump bad stuff in the river, and bad stuff flows downstream.

  • In a lake, go as far as possible from a village or campsite. A river that feeds the lake is generally better than the lake itself.

  • Limit water with lots of silt, mud or sediment. Sediment will eventually clog almost any filter or purifier. You can let sediment settle in a large bottle or bucket before filtering it- this takes several hours.

  • Use Alum to get the sediment and dirt to settle quickly. Alum is used as a cooking spice and is found in baking powder. A small quantity of alum causes dirt to fall to the bottom of a container quickly. Filter the clear water without disturbing the dirty stuff at the bottom or top.


Where in the World is Water Unsafe?

Photo courtesy of GRAYL

Waterborne impurities and water treatment standards vary widely. In general, the “Developed World” has safe tap water and the “Developing World” doesn’t; however, there are lots of exceptions. If you find yourself in a city where locals buy big jugs of bottled water, you probably should bring a water purifier along.

Always assume untreated (river or lake water) is unsafe before treatment!

Dig Deeper:

  • The Centers for Disease Control (CDC) has specific info on every country’s drinking water here. Click on the country, then expand the “Eat and drink safely” section.

  • NeoMan Studios made a nice graphic about safe and unsafe drinking water.


Industrial chemicals, Heavy Metals, etc.

Photo courtesy of GRAYL

Chemicals and heavy metals may not be detectable by sight, smell or taste. Luckily, a filter or purifier with activated carbon removes many chemicals and heavy metals.

Don’t take my word for it:

You can find dozens of articles about cities with folks in Hyperabad and Mexico City who are worried about chemicals in their drinking water. I don’t blame them.


What are all the nines? (99.9%, 99.9999%)

Photo courtesy of GRAYL

Filter and purifier manufacturers describe how many pathogens they remove with a percentage. Within reason, the more nines the better.

The US Environmental Protection Agency set minimum reduction standards, intended to guarantee that no more than 1 person per 10,000 will get sick. Your filter or purifier should remove at least:

  • Bacteria – 99.9999%

  • Protozoa – 99.9%

  • Virus – 99.99%

Dig Deeper:

  • Cascade Design (makers of MSR Filter Products) has some advice for interpreting the nines.

  • CDC advises on filtering Cryptosporidium (protozoan cysts)


Purification/Filtration Methods

Photo credit: Jacqueline Trujillo

Below is a list of options for removing/killing impurities from your water.

  • Boiling

    • Pros: No special tools needed, kills all pathogens

    • Cons: Slow (including time to cool), doesn’t remove chemicals

  • Chemical treatments (chlorine, iodine, bleach, etc)

    • Pros: Small and easy to carry, great backup option

    • Cons: Don’t kill Protozoa (Crypto, Giardia), taste bad, may not work in cold or cloudy water, slow (30+ minutes), doesn’t remove chemicals

  • Ultraviolet light (UV)

    • Pros: Small and easy to carry

    • Cons: Does not work in cloudy water, doesn’t remove impurities

  • Camping Filters

    • Pros: Several form factors, light and small

    • Cons: Do not remove virus, some do not remove chemicals

  • Camping/Travel Purifiers

    • Pros: Removes all pathogens, some remove chemicals

    • Cons: More expensive than more basic filters





Chemicals & Heavy Metals

Works in cloudy water







Chemical Treatment





UV Light





Camping Filter





Camping/Travel Purifier






Dig Deeper:

  • Here’s an in-depth review of water purifying options by HowToWildeness

May 21, 2017

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