Growing up my dad and i boiled all our water. As i found out this is bad for ultralighters because of the extra fuel. I was going to use iodine pills but a friend told me that it was bad for the liver over time. Chlorine dioxide might also be bad for the liver over time, but the fact that lots of water for the public is treated with Chlorine dioxide i would assume it is safe. PLus it doesn't taste as bad.

I have gone whole hiking trips on the PCT without filtering, thought this was when snow was melting. My rule on treating or not treating is if i can see where the water has traveled and if it hasn't gone threw a flat field where cows could possibly roam then i dont filter or if the water is clearly snow melt. I rigged up a screen that keeps the big floaties out. If i dont know the area where i am hiking i always bring a filter and Chlorine dioxide. That me, and i have never caught a bug.