Without getting to technical, we can throw out all the science and look at it from a simple point of view. If you don't drink water for 3 days your liver won't function and you can die from that alone. Plain and simple.

I don't measure how much I intake daily, but you can bet that I'm always hydrated. Everyone must listen to your body. If you are really keen on that aspect, you will react and drink water every so often. A dry mouth, itchy eyes, headaches, hiccups, your dripping sweat on a hot day......all of these signs are telling you that you need to drink water.