I used Polar Pure in '94 after my cheapo Timberline filter stopped working 50 miles from Springer. A friend of mine had an extra bottle that he had used for years. The fact that this same bottle lasted me all the way to Katahdin illustrates the main reason Polar Pure is used by so many hikers: never runs out, never breaks, really easy. It does have an iodine taste, though it is much less strong than iodine tablets. Adding a little vitamin C to the water after the required disinfection time reduces the iodine taste.

Some thru-hikers are carrying small squeeze bottles of bleach to treat their water. One or two drops per quart seems to be the norm. I used bleach a couple of times but didn't like the taste even at the one drop per quart level. I recently (9/25/03) read an article documenting bleach's use during a humanitarian crisis: 4 drops per quart & 30 minutes contact time. It then went on to say that if you couldn't clearly smell chlorine after the contact time, repeat treatment.
Quite frankly, given other options I would never choose to use bleach.

AquaMira is a chemical disinfectant employing an oxidizing chemical (chlorine dioxide). You can't buy AquaMira in the state of California yet. The McNett Corporation, AquaMira's producers, hope that California will complete its review of the product by the end of 2001. It had the least taste of all the chemical disinfectants. Chlorine dioxide's oxidation potential, which is directly proportional to its ability to kill pathogens, is greater than iodine and chlorine. AquaMira is my personal choice for chemical purification. I have about 1,500 miles on the same set with no problems to report.

I also carried a Pur Hiker for about half the trail during my 2000 southbound hike. It's a nice thing to have, but I don't think it's worth the extra 3/4 of a pound as compared to chemical purification. There is an argument for filters, however, whose main idea is that a filter allows you to drink your water immediately right at the source instead of carrying water while you're waiting for the disinfectant to work (20 minutes). By not carrying drinking water (1 qt - 2 lbs) you're actually carrying less even though the filter weighs 13.5 oz. Many other filters, besides being heavy, will clog up on you. Don't get fooled into thinking you need a more "expedition" worthy filter for your thru-hike by the sales people at your local outfitter. Expect to have to replace the cartridge during your thru-hike. The good news is that, as of the writing of this article (Sept 7, 2001), PUR has a one year no-clog guarantee. In other words, if you buy your filter before a thru-hike, they will keep you in filters for the duration of your hike. Cleaning the filter will extend the life of a cartridge considerably.

The final option, choosing your water sources carefully, is kind of a hit or miss thing. I don't treat all my water, but then again I also think that eventually I'm going to make a poor judgment and get parasites. One of the few things I carry in terms of medicine, though, is the cure for giardia and cryptosporidia: Metronidazole (trade name = flagyl). I had giardia for 2 1/2 years while I was in the peace corps, and though not fun it isn't something to be terrified of. The medicine is a toxin, however, so don't use having a course of it as a substitute for careful judgment of water quality.