While it's certainly possible to get water borne illnesses, the likelihood of that happening is low. Otherwise humanity would have died out long ago. Quoting fr

While it's certainly possible to get water borne illnesses, the likelihood of that happening is low. Otherwise humanity would have died out long ago. Quoting from http://bwca.cc/tripplanning/waterfiltration.htm http://bwca.cc/tripplanning/waterfiltration.htm : > Thirty years ago, we didn't fret about lake-water microbes. We just drank the water straight or spiked it with iodine. Today, that is changed. Many of us grip our water filters and cautiously take a sip. In fact, Giardia and other water-borne pathogens often star in those scary mind-flicks we conjure from bears, bugs, and huge, wind-swept waves. > Don't get me wrong. I'm not saying that six months of recurring diarrhea isn't something to ponder. Just don't panic if you swallow a mouthful of lake water. The Boundary Waters isn't a New York sewer. Much of the water is clean. The problem is, we can't distinguish the clean sources from the dirty ones. > That's why I filter, boil, or chemically disinfect the water I use for drinking, washing dishes, and brushing my teeth. On the other hand, canoe-country author Michael Furtman has roamed the Boundary Waters for nearly 40 years, and hasn't treated a drop and has never been sick. He's not alone. Quite a few Boundary Waters old-timers and wilderness guides drink the water. But they are careful about where they collect it. In any case, my water filter for camping is only a ceramic filter. It doesn't change the oxygen or CO2 levels. If TillE's proposal is correct, the output after filtering should still be 'stale'. What you said about well water is true, but my examples were structured to avoid ground contamination. If you collect rainwater, and let it sit for a day, does it taste 'stale'?