Learn everything you need to know about safe drinking water before your trip. Contaminated drinking water is the most common source of health problems while traveling. Gastrointestinal distress is the most common symptom. Unfortunately, the mere inconvenience of multiple trips to the bathroom isn't the only thing to worry about. Contaminated water can also cause bacterial diseases.

Bottled or Boiled Water
You're up against a varied army of potentially injurious contaminants while traveling. Luckily, there is something you can do about it: avoid the local tap water. Most microorganisms are killed when boiled sufficiently, and bottled water is generally available.

Bugs, Parasites, and Other Contaminants
Some common bacteria found in drinking water include E.coli, cholera and salmonella. These can be killed be filtering and with chemical treatments. Protozoa include giardia and cryptosporidium, and respond well to filtering due to their relatively large size. Viruses include hepatitis A, polio, and rotavirus, and are very difficult to filter due to their very small size; chemical treatment works best for viruses.

Additionally, chemical pollutants, particles and debris, and other contaminants can cause problems. These are less likely to respond to boiling, and may require a combination of treatments.

These conditions are not limited to developing countries. Cryptosporidium outbreaks have appeared in the U.S Midwest and Northwest, and even Scranton, Pennsylvania, as well as in highly populated cities in Australia. Giardia is found in the water supply in St. Petersburg, Russia.

Some cities may advertise their drinking water as being chlorinated; this doesn't necessarily mean that the water is contaminant-free. Your best approach when faced with potentially unsafe drinking water is avoidance.

What You Can Drink
In addition to bottled and boiled water, tea, coffee, canned soda and juice, beer and wine are generally safe.

Brush your teeth with safe water
Brushing your teeth with contaminated water will have the same effect as drinking it outright. Don't brush your teeth in the shower. Use bottled water.

Avoid Ice
Freezing water does not kill bacteria. A margarita on the rocks may sound appealing, but ice cubes present the same problem that tap water does. You can make your own ice if you boil the water first.

Contact Lenses and Dentures
You don't need to drink contaminated water to be exposed; always consider alternate sources of exposure. Wash contact lenses and dentures in water you trust.

Water Purification Tactics
Boiling water is an effective tactic for removing all parasite contamination. Water should be boiled for at least 10 minutes or longer, especially at high altitudes, where the boiling point will be lower, and some parasites might not be killed as quickly. Allow any sediments and particles to settle before drinking, and then decant the water from the top into another container.

Immersion coils are cheap and the work well. Magellan's sells these and most of the other products mentioned below.

Tablets
Commercially available iodine or chlorine tables work well. However, long-term use can cause these compounds to build to unhealthy levels. Additionally, iodine and chlorine do not remove particulate contaminants, are unhealthy for pregnant women and thyroid patients, and do not kill some parasites, such cryptosporidium.

Iodine is the more effective of the two solutions. Potable Aqua, composed of the iodine compound tetraglycine hydroperiodide, is the most popular brand of water purification tablet. Read directions on all tablets systems for tablet-water ratios and dissolving times; 20 minutes or more may be required for the tablets to dissolve completely, especially in colder water.

Chlorine Bleach
If you do not have tablets, two drops of common chlorine bleach in a quart of water will help as a last resort.

Water Filters and Purification Pumps
Outdoor stores like REI carry water filters and purification systems. It is essential that the filter system you choose is suited to your needs. A filter with an insufficiently small pore size, or one that is not designed to filter viruses, may permit some contaminants to get through.

Filter/Chemical Combination
Bacteria are more easily filtered than viruses, but are resistant to chemical treatment. The opposite is true for viruses. Many filtering/purification systems combine the two methods. You can combine the two on your own by using a filter and chemical (iodine) treatment.

The Steri-Pen
A new product is on the market which will enable you to disinfect water quickly and discreetly in any restaurant or hotel while traveling. It uses ultraviolet light to disinfect, and is portable, so you can take it anywhere. We highly recommend this to anyone who frequents areas where the water is suspect, particularly if you plan an extended stay.

Hot Water Bottles
Prolonged exposure to higher temperatures will kill many parasites. Drinking from a hot water bottle is slightly safer than drinking untreated, cold water.

When to Damn the Torpedoes
If locals are drinking the tap water without ill effect, there is no known occurrence of giardiasis, and you are going to be staying in one location for four weeks or more, you may want to drink the water to allow your body to acquire some of the local microbes. Start slowly and allow your body time to adapt.