I think with reasonable care, almost any approach can be 98% effective unless you are unlucky. On my third thru hike now and I still carry a filter because (1) I have seen statistics about water quality - esp. in New England, and (2) I worry a bit about ingesting lots of chlorine or iodine. In the south, I drink untreated water from almost all piped springs (there aren’t many in the north) unless something looks fishy uphill. I think/hope that is safe. I wouldn’t dream of drinking any stream or lake water without treatment. As others said, a filter is prob. more reliable when properly used. Still, there is the splash factor, and you get water on your hands, etc – or you put your filter in a bag so the inlet and outlet hoses touch. So, you can still be unlucky and get bugs. I got giardia once – three days after I finished at K in '99. It was good to be at home so I could move the TV into the bathroom. Good news: metranaz. gets rid of the bugs in just a couple of days. Also, First Degree hiked from Pine Grove to Peters Mtn with giardia – wasn’t a pretty picture but it worked! ('Guini: got my son for a rabbit now – the little prick ditched me once but I caught him. So, we are 23 days to Damascus. Packs are down to 14-16 lbs loaded. This super light stuff is FUN! No pain, don’t have to watch your feet, etc. Still haven’t figured out how you got to 7lbs - did you eat? Zero day and beer today.)
old man