Rainwater collected in clean containers or in plants is usually safe for drinking. However, purify water from lakes, ponds, swamps, springs or streams, especially the water near human settlements or in the tropics.

When possible, purify all water you got from vegetation or from the ground by using iodine or chlorine or by boiling.

Purify water by:

* Using water purification tablets. (Follow the directions provided.)
* Placing five drops of 2 percent tincture of iodine in a canteen full of clear water. If the canteen is full of cloudy or cold water, use 10 drops. (Let the canteen of water stand for 30 minutes before drinking.)
* Boiling water for one minute at sea level, adding one minute for each additional 300 meters above sea level, or boil for 10 minutes no matter where you are.

By drinking nonpotable water you may contract diseases or swallow organisms that can harm you. Examples of such diseases or organisms are:

* Dysentery. Severe, prolonged diarrhea with bloody stools, fever and weakness.
* Cholera and typhoid. You may be susceptible to these diseases regardless of inoculations.
* Flukes. Stagnant, polluted water — especially in tropical areas — often contains blood flukes. If you swallow flukes, they will bore into the bloodstream, live as parasites and cause disease.
* Leeches. If you swallow a leech, it can hook onto the throat passage or inside the nose. It will suck blood, create a wound and move to another area. Each bleeding wound may become infected.