I think you should drink 5 litres of water per day. Sounds much? Well, I wouldn't suggest anything less. Read that in a book about yoga I really trust, so... You should drink in small intervals. Like a glass of water every 20 minutes.
You should calculate like:
25cups/16 hours of wake time = 1.5625 cups per hour which means you should drink 1 or two cups per hour while writing down every cup you make as I assure that drinking 5 litres of water is
minimal and if you don't have the discipline to drink all the water than rather don't
On the bright side I could be wrong and it might be three litres. But I still strongly recommend that you go for 5.
On even brighter side I tried it and lost 3 pounds but I'm at ideal weight which means that it really works wonders at higher weights.
I'm sure you'll succeed and good luck!