• Water should be brought to a vigorous rolling boil for 1 minute and allowed to cool to room temperature-do NOT add ice that could be made from contaminated water. At altitudes >6,562ft (2km), boil for 3 minutes.
• Adding a pinch of salt to each quart of water or pouring the water several times from one clean container to another will improve the taste.

• The CDC suggests using a dose of approximately 5mg of iodine per quart or liter for clear water, but doubling to 10mg if the water is cloudy or cold. Each Potable Aqua® iodine tablet provides 8mg of iodine. Therefore, one tablet per quart or liter should be sufficient for clear water. However, if the water is cloudy or cold, use the maximum of two tablets per quart or liter.
• Read the iodine product instructions for proper disinfection technique. Cloudy water should be strained through a clean cloth to remove any sediment or floating matter and then treated. Attempt to warm extremely cold water (<5°C or 41ºF) to increase the iodine’s effectiveness. However, the CDC suggests if the water is very turbid (cloudy) or very cold, use the maximum iodine dosage and the contact time with the iodine may need to be increased from 30 minutes to several hours. Thirty minutes contact time is adequate when water temperature is at least 25ºC or 77 ºF. Double the contact time for each 10º less than 25ºC in water temperature. Therefore water that is 15ºC or 59ºF needs a contact time of 1 hour and a temperature of 5ºC or 41ºF needs 2 hours.
• Iodine disinfection cannot be relied upon to kill Cryptosporidium. Also, Giardia oocysts (eggs) are relatively resistant to iodine. (See section below on use of portable filters.)
• If iodine-disinfected water is the only water available, it should be used for only a few weeks. It should not be used by persons with thyroid disease or an allergy to iodine.
• Conclusive data on the safety of iodine in pregnancy are not available, therefore it’s use is NOT recommended for pregnant women.
• Chlorine’s effectiveness in killing microorganisms varies greatly with factors such as pH, temperature, and organic content of the water, making it less reliable than iodine. Note too that chlorine can damage the membranes in some filters.

Portable filters provide various degrees of protection.

Most portable filters have an absolute pore size of 0.1 to 1 micron therefore do not effectively remove viruses, making chemical disinfection still necessary.  Therefore, using a filter with an absolute pore size of 1micron or less and adding iodine is an effective treatment for all waterborne pathogens.  Most camping equipment suppliers stock portable filters with 0.1 to 0.5 micron pore sizes that range in price from $35 to $200.  A new filtration technique using a hollow fiber membrane offers a very large filtering surface area in a very small volume. The filter can fit inside of a water bottle.  Sawyer® Water Purifier (Viral) is a portable filteration device that physically removes viruses as well as protozoa and bacteria, making chemical treatment unnecessary. 

Last resort Water that is too hot to touch (above 65o C or 149o F) will be safer than cold tap water. Water temperatures of 64o C (148o F) or higher held for at least 2 minutes will render Cryptosporidium noninfectious. Giardia cysts are inactivated after 5 minutes in water at 55o C (131oF) or immediately in boiling water. Note that freezing will not kill Cryptosporidium oocysts, but is effective against Giardia.

Reviewed: July 2008