That's 3.8L per day [(24 hours - 8 hours sleeping) * 8 fl oz = 3.8L]. Recommended intake is 2-3L[1]. Just be careful of water poisoning...
[1] http://www.mayoclinic.org/healthy-living/nutrition-and-healt...
My case is a bit unusual as I'm far above average in height and weight. On average, the recommendation for my size is around 5.0L/day. In relation to that, the top of my head figure of 3.8L seems like a good lower bound.
It's always interesting trying to do conversions in a world made for folks are 5'8" and <200lbs. I'd be shredded to the bone if had a 'healthy' BMI and I'd be dropping pounds a week on a 2000 calorie diet.
Of course, drinking anywhere near 25L is not 'safe' either, and can still cause electrolyte abnormalities, neurocognitive dysfunction, seizures... Stick to the recommended intake, adjusted for water losses during significant exertion or high temperatures.