...Not that much... 3ish liters spread out over the day is good. Too much water will strip your body of electrolytes and salt.

I recently upped my water intake and can report that my skin and mood feel better. I caffeinate with a strong coffee and 2 cups of tea in the morning, and around 12 I switch to pint glasses of water every 2 hours or so until 6-7 o'clock.