What's the Most Frugal Way to Filter Your Water?

I'm curious to know your thoughts on what you think is the most frugal way to filter your water - buying bottled water, filtered water pitchers, faucet-mount filters, etc. I don't have a refrigerator with a water filter built in, and we have well water. We've been drinking the well water for years and have never been sick from it, but I've always wondered how clean it really is. I came across this contest for bloggers to win a Zuvo Water Purifier, and they actually have a comparison chart comparing the cost of bottled water vs. pitcher filters vs. faucet mount filters. I'm wondering if it's an accurate comparison for couponers, though! Right now I have quite a few packs of bottled water at home that I've "bought" for free! Obviously, though, I wouldn't be able to get bottled water free every time.

So what do my fellow couponers and frugalites think? Do you think the cost of something like a Zuvo would be worth it in the long run, or do you think another way would still be cheaper? I'd enjoy hearing your thoughts on the matter.