Simplified, my position is that there are three kinds of water sources: pristine and pure, potentially contaminated, and contaminated beyond most treatment methods. Most of the time, pristine sources are available where I hike and I do not treat these sources. Plus, I totally avoid obviously contaminated sources. When the source is potentially contaminated (e.g., areas frequented by humans, pack animals, domesticated animals or wild animals), I treat.
I take a fairly relaxed attitude towards water treatment because I have made life decisions that allow living near and hiking in many relatively uncontaminated wilderness areas. Generally, it is easy for me to carry enough purified water from home to get far enough into the backcountry beyond most contaminated sources. By referring to relatively uncontaminated areas, I mean that my research has lead me to believe that any contaminants in these backcountry areas (especially protozoan cysts) are in such minute quantities that they are unlikely to cause serious problems. Part of this attitude is based on the belief that I have a fairly strong immune system to deal with potential contaminants. If my general health declines and I become more susceptible to illness, I would have to reconsider. Most important, I am willing to change my rather relaxed attitudes about water treatment when confronted with new information.
Part of my more relaxed attitude towards water treatment is because I believe I have developed a better understanding about which water sources to trust and not to trust. Here is the link to a short article on the results of my research: Avoiding Poor Sources of Drinking Water. For example, most hikers assume that if a water source is clear and cold and running briskly that it has a low probability of being contaminated. This common attitude is not defensible. In general terms I carefully plan my water treatment regimen around my knowledge of potential water sources in the areas in which I am hiking.
Having said all this, I occasionally take trips into areas that might have been compromised. I also take trips with those who feel strongly about water treatment and who insist on treating all of our drinking water. In both cases I willingly participate in treating all of our group water containers. On these trips, we carry not only a primary, but also backup water treatment methods.
As a backup, I always carry chemical water treatments (usually chlorine dioxide) if I can’t find dependable sources of water. However, in using chemicals one needs to be careful about the timing: use the chemicals before getting desperate. It is good to carry chemical water treatments for another reason: treated water is an effective hand and surface sanitizer as well as a potential source for cleaning wounds in the field.
Since it is likely that more people get sick in the backcountry from poor personal hygiene than from questionable sources of drinking water, I have become quite conservative about personal hygiene. I seldom share food with others for the same reason. I do what I can to encourage others to take their personal hygiene seriously in the backcountry.
To get an understanding of the reasoning behind the above conclusions about water treatment in the backcountry, consult this much longer article on the topic, To Treat or Not To Treat The Water? The sub-topics listed below are developed in this detailed article:
Working Definitions—Two Competing Approaches
Philosophies of Water Treatment: A Continuum
Reader Participation: Philosophy of Water Treatment
Arguments in Favor of Relaxed or No-Treatment Approaches
In Favor of Conservative, Disciplined, Hard-Line Treatment
Final Thoughts About Treatment
Additional Issues for Reflection