I have read that you should drink a minimum of 8 glasses of water a day...so I guess that must be around a liter or so. I also read that you can never have too much water. So drink away!
The amount recommended by nutritionalists is 2 litres a day of still water, not including tea, coffee or juice. However, if you are exercising vigourously or live in a very humid climate the recommended amount could be as much as 6 litres.