"Boiling does not guarantee that your water becomes safe to drink." I suppose this is logically true, since boiling will not purify water contaminated with arsenic or other heavy metals. But for the usual biological conaminants like bacteria and viruses, boiling is the best way to go. No water treatment pill or filter will protect as effectively as boiling against the total range of biological contaminants. I am a fan of boiling since I have effectively purified some very nasty water sources with it.

However, boiling does have its drawbacks. It takes a long time,especially for large quantities. In some situations, fire may not be an option for safety reasons. So it is prudent to have some other options - my prefered backup is a filter. Iit is fast, and the water is still cool when you are done. But be sure you know what agents you are trying to defeat.