Water Precautions

In developed countries, clean drinking water is available out of the tap, and breakdowns in the system are rare. Developing countries, however, don't always have the resources needed to ensure a pure water supply; consequently, tap water is not safe to drink. Even if the local population can drink the water, travelers should not assume that they can. Local residents have built up some immunity to organisms in the water, but visitors have not. As a result, tap water can make travelers sick.

When traveling through areas with less than adequate sanitation or with water sources of unknown purity, travelers can reduce the chance of illness by observing the following precautions.

Use sealed bottled water or chemically treated, filtered, or boiled water for drinking and for brushing teeth. Drink beverages made only with boiled water whenever possible (such as hot tea and coffee). Water boiled for any length of time at sea level (even 1 minute) is safe to drink.

Drink canned, boxed, or commercially bottled carbonated water and drinks. International brands are safest. Beware of unsealed containers that may have been refilled. Beer and wine are safe to drink; however, alcohol added to other beverages does not render the beverages safe.

Purify water (see Treating Water) if one of these options is not available. Decide which method to use for water purification and bring along the appropriate equipment. Carry safe water if going out for the day in an area where availability of safe water is not assured. Don't assume that water is safe because it is chlorinated. Chlorination does not destroy all the organisms that can cause illness.

Continue to breastfeed infants who are nursing because it is the safest food source for these infants. If formula is used, prepare with boiled water and sterilized containers.

Avoid tap water or anything mixed with tap water and don't rinse toothbrushes in tap water. Don't drink fruit juice unless it comes directly from a sealed container; otherwise, it may have been diluted with tap water. Don't drink from wet cans or bottles; the water on them may be contaminated. Dry wet cans/bottles before opening and clean all surfaces that will have contact with the mouth. Don't use ice unless it is made from boiled, bottled, or purified water. Freezing does not kill the organisms that cause diarrhea.

Treating Water


High temperatures kill most germs quickly. Boiling is always a reliable method for killing all of the common intestinal pathogens in water. Urban travelers may choose an immersion coil for boiling water (a plug adapter and current converter might be necessary). Boiling for 1 minute is usually sufficient. Because the boiling point decreases at higher altitudes, water should be boiled for 3 minutes at 2,000 m (6,600 ft).

Chemical Disinfection

If boiling water is not possible, chemical disinfection is an alternative. Most (but not all) diarrhea pathogens are susceptible to being killed by iodine, which can be used to disinfect water, leafy vegetables, and fruits. Add 5 drops of 2% iodine to 1 liter of water and let stand for 30 minutes.

Travelers who have thyroid problems or iodine allergies or who are pregnant should not use iodine for water purification. The use of iodine should be limited to a few weeks to avoid its effect on the thyroid from long-term use.

For those travelers who wish to avoid the taste and smell of iodine in their disinfected water, vitamin C (ascorbic acid) can be added to the water after the iodine has been in contact with the water for 30 minutes or more. Add about 50 mg of vitamin C to a liter of water and shake briefly to eliminate the iodine taste and odor.

Tetraglycine hydroperiodide tablets (e.g., Globaline, Potable-Aqua, Coghlan's) are available from pharmacies and sporting goods stores. The manufacturer's instructions should be followed.

Chlorine also can be used for water purification, but its germicidal activity varies greatly with temperature and other factors and therefore is less reliable than iodine.

Portable Filters

It cannot be assumed that portable filters will make drinking water safe; most authorities make no recommendation regarding their use because of insufficient independent verification of efficacy.

However, in areas where boiling all drinking water is not practical, a good quality filter with a pore size of 0.1 to 0.4 microns will effectively remove cysts and bacteria but not viruses. The filtered water should then be treated chemically as well.

Ultraviolet (UV) Light

UV light can kill bacteria, viruses, and protozoan oocysts in water. Battery-operated, portable units that deliver UV doses have become available and may be useful for disinfecting small quantities of clear (not cloudy or turbid) water.