This is all dependent on your level of exercise and rate of perspiration. A 72kg person would have to drink around 6.5L of water for it to become dangerous[1].

This is all dependent on your level of exercise and rate of perspiration. A 72kg person would have to drink around 6.5L of water for it to become dangerous[1]. [1] http://www.sciencelab.com/msds.php?msdsId=9927321 http://www.sciencelab.com/msds.php?msdsId=9927321