Question: how much water do you have to drink for it to be harmful?
Answer: Finally, according to one report, a 9-year-old girl developed water intoxication after consuming 3.6 liters of water in 1–2 hours. Bottom line: The kidneys can remove 20–28 liters of water per day, but they cannot excrete more than 0.8 to 1.0 liters per hour. Drinking more than this can be harmful.