Water is pretty high up there in the list of needs. Fortunately, here in Wisconsin, and in many places along the National Scenic Trails, there are filterable water sources. You can extract it from the wilderness around you. This way you don't have to lug as much at one time, which is a Pretty Big Deal, seeing as how water's one of the heaviest things you'll carry with you. But, there's a lot that can go wrong with untreated water. Plenty of chemicals, viruses, bacteria and other nasties hiding in there. So I did a lot a LOT of looking at water filters.
First off, I chose based in no small part on some of the places that I intend to use this. The Ice Age Trail isn't nearly as remote as some places of the Appalachian Trail, Pacific Crest Trail or Continental Divide Trail are. Parts of it run directly through towns and suburbs. And where it's not near town, it may well be near a farm field. Not going to go pumping water right out of a puddle in the cow pasture if I can help it, but still, the field feeds the ditches, the ditches feed the streams and creeks, and all that water's gotta go somewhere. So if I'm pumping out of a river, and it turns out that two miles down the road they just sprayed manure or fertilizer, I want a filter that gives me some degree of safety against that.
Enter the MSR Sweetwater filter. It's 0.2 micron pore size filters out all manner of bacteria, cysts and protozoa. That alone would be good enough for most, but as the spec sheet there indicates, it also filters out chemical toxins from the water. And it's not just the mechanical filter, it's also got a second stage, sodium hypochlorite drops. Essentially concentrated bleach. You just add them, I believe 5 drops to a liter, to the filtered product mix it up a bit and give it 5 minutes. This takes care of the viruses that are far too small for the filter to pull out. In addition to the main filter, I picked up the SiltStopper prefilter which just attaches to the filter line and keeps out anything roughly 25 microns in size. Easier to purge or clean than the main filter, and anything that saves mileage on that, is worth it to me. As a final line of defense, I picked up a in-line activated carbon filter for my Camelbak. Not designed to stop bacteria, but I take comfort knowing I've got it on hand incase I'm leery of a source and want an extra step to catch chemical contamination.
It's not the lightest filter, infact it's rather bulky compared to something like a sawyer mini. But the mini uses hollow fibers to filter the water, and is primarily aimed at stopping the bacteria,parasites and protozoa. The drops are superior to other chemical treatments in terms of taste, something like iodine or aquamira definitely alters the taste. Also popular are the MSR and Platypus gravity filtration methods. You can even convert a Sawyer Mini into a gravity feed system. These have the advantage of not having to pump. But, I find that when pumping for my own needs, maybe another person's, that it filters plenty fast, and the pump motion isn't half as hard as all the alarmist reviews seemed to make it sound.
It came with no manual, I had to work out everything myself. No big deal, I have the internet. Couldn't figure out what one of the pieces was for a long while... then I got it. it's a nalgene bottle adapter. Also comes with an intake hose, a screen filter, filter cartridge, pump section, cleaning brush, and finally the output hose.
The water it filters tastes good, I suspect it's filtered to a higher standard than what comes out of my faucet here at home. I don't detect any chemical taste from the drops, and it didn't taste like I would imagine a lake tastes like either. I did find it was harder to get the filter going in water that was moving fast enough to tug at the filter line. But I drank easily 140 ounces of it, and cooked with it as well. A day later, I'm feeling fine. I have great faith in that filter's abilities, and didn't hesitate to drink the water I filtered with it.