My son is planning a section hike on the Appalachian Trail in a few months and asked me the other day if I had knowledge of the canyoneering community's approach to water purification. Knowing the western back-country to have its share of hydration challenges, especially for multi-day excursions - he figured this would be a good resource for ideas. He then pointed to this article which contains a water treatment study for long distance hikers. Surprising number of folks that throw caution to the wind and don't treat at all. Is Water Treatment Necessary? Teaser I found a few scattered references on the collective, nothing real current or concentrated. I've always trusted a First Need filter system, hasn't let me down yet. Just curious, what's your method - filter, chemicals, both...neither?