Right. I think this is one of the benefits of experience; thinking about water sources before the trip. It is almost mandatory here in Arizona. I do a lot of spring, early summer and autumn hiking in desert mountains and cattle country. Mostly there is no flowing water, it is usually found only in water pockets or murky pools. So, I generally and routinely use a filter followed with Micropur tablets. When the water, after filtering, is the color of urine, or tea, one feels the need to do a bit more with it before drinking. I need to clean the filter a lot also; up to two times per liter. Once in the Grand Canyon I took water from a small pool with a dead coyote floating in it: no real alternative. I also carry a lot of water if the need arises.

Sometimes I think a person could gain weight by drinking Arizona mountain water straight, without treatment, if they didn't get sick first. There is probably 100 calories per liter of critterhood swimming in, and just soaking in the sources.

In the summer and early fall, I generally spend 2-3 weeks and 2-3 trips in the Sierra. There, I will use a Steripen or filter when I am mostly in popular (crowded) areas. I like the Steripen but don't trust it entirely. Otherwise, I don't treat the water at all if I have a good idea of what is upstream. On my trips to more remote places, I leave the water treatment machinery at home. If in doubt, I'll drop in a Micropur tablet.

Up until about ten years ago, I never treated my water at all unless it really looked bad. Then I would boil it. I don't recall ever getting sick: well, once when I was in the Army I picked up a case of amoebic dysentery in North Carolina from drinking contaminated water. I suspect that, in over 60 years in the hills, I have developed resistance to some of the more common bugs.