I've mentioned that I pass 4+ liters of water when I do 24 hour urine collections for analysis. I've always consumed lots of water, but until bottled water hit the shelves, I never carried anything to drink in my car. These days I won't leave home without it. It is odd.
As
@Ken Anderson said, you can really screw up your electrolyte balance by diluting the mineral concentrations in your system. I keep Pedialyte on hand for hot days when I might be drinking more than normal.
Interesting that I asked my nephrologist about my high water consumption (4 liters per day) and he said it was not high enough to worry about: "Your nephrons love water." It still wasn't enough to prevent kidney stones.