So I'm planning a thru hike next spring and I've been thinking about water treatment. I have a steri pen adventurer (wonderful for traveling around S. America). I was wondering who uses one the AT. How available are those special batteries in towns along the way (we'd rather not have to rely on mailing things)?

On the Colorado Trail last year our pump broke midway through so we bought a steri pen in one of the towns. It was awesome! and the batteries lasted the week or two we needed them to, but some where on the AT we will need to replace them.

In Colorado almost all of the water was crystal clear, how much of a need is there for a pre-filter on the AT?

any other general musings on water? (but don't turn this into a "Just Use AquaMuira" thread I know the advantages/disadvantages of chemicals)