Interesting. 3l is about 12 cups.

I remember back in the 80's and 90's Dr. Dean Edell on his talk show routinely tried to bash this "8 cups of water a day" rule of thumb as an urban legend.

He says in this 2002 post that your body weight * 0.08 is the approximate number of cups of water you should get, but I think that includes all that you normally get from food too.