More harm than good by too much water intake?

So we are finally told there is no evidence to support the notion that drinking at least 8 glasses of water everyday is good for health. On the contrary drinking too much water it seems could probably put a strain to our kidney. I wonder why it takes so long for the medical authorities to figure this one out. It seems strange though that no one question the recommended amount of water for drinking daily, why 8 glasses and not 10 glasses or 5 glasses? Apart from that the fluorine and chlorine added to the water for drinking is harmful to human and may probably cause serious side effects such as cancer. I wonder what’s next on the table? Perhaps we should avoid taking hot shower?

8 glasses a day?