Originally Posted by deltav

I spend a decent amount of time in the mountains, so a word of warning. Even in the purest of pure alpine snowmelt springs in a high mountain vale you can get beaver fever aka giardiasis, because some small animal pooped or died in a crevice somewhere which trickled down to your spring. It's *unlikely* in some settings and you might happily suck down that fresh H2O for a while..... but after the first time you wind up projectile vomiting and shitting in the wilderness for 3-4 days straight and then struggling with digestive problems for months and sometimes years after, you'll decline to take the risk from there out. Purifiers FTW in most cases.