Hi Rob, I don't think I would be packing all my water on a Smokies overnighter. There is water everywhere, in fact on some trails you'll be wishing you were in the Sahara after crossing the same stream ten times in a mile or two! Seriously though, you will need some type of collection strategy and treatment method, although on overnighters I have used a few methods that I wouldn't use on a longer trip. Typically I carry a Steripen, but for a short trip like this boiling combined with tanking up works fine. Here's a strategy:
-on the way to the traihead, start hydrating. I usually drink a cup of coffee when I get up, and I have a couple liters of water in the truck with me just for drinking on the drive. Tony's right, storing water in your body is better than storing it in your pack.
-I usually carry 1-2 liters of water on the trail depending on available water sources. If there are springs and seeps (and there are hundreds in the Smokies) I carry less. It requires a little experience and a good understanding of your surroundings to use springs and seeps without treating; I use them alot, usually don't treat, and I've never gotten sick. I'm very cautious about knowing what's around the water source, especially uphill. I also grew up on well water, so I'm not conditioned to all the municipal treatments most have in their water.
-Use only collected water to cook with; you're boiling it anyway so no need to treat it. I try to camp close to a good water source, and often I'll just boil my next day's water supply while cooking. Doesn't take long to boil a liter or two, and if you are only doing this one night, doesn't use much fuel either. I wouldn't do this on a long trip, nor if I were cooking with alcohol or esbit, but since I'm a canister stove user, I typically have more than enough fuel along if I'm only out one night.
-take along a couple MicroPur tablets or some aqaumira, just in case. I hate the stuff and it often gives me terrible stomach cramps, but if I had kids with me, I would rather they get stomach cramps than giardia/crypto.