So (ideally) you learn something every day. Today I was flipping around radio stations on the way to work and came across a segment about the conventional wisdom of drinking eight glasses of water a day to help your body purge toxins. Now, I've never felt particularly strongly about it, but I had no concrete reason to believe that it wasn't true.
Turns out, it's bunk. This page gives the gory physiological details, but the short of it is, you really don't need to worry about drinking a specific amount of water. If you drink when you're thirsty, you'll be fine. In fact, for some people, drinking that much water will actually reduce the effectiveness of your kidneys slightly. Imagine that.