No, these are reactions that take place regardless if you're doing a triathalon or sleeping. Lern2science.
You know what? Stop pulling things out your ass. I was born in south africa. I went to JROTC bootcamp. I happen know these things.
You know where all that excess water you drink goes? Reserve, for sweat, tears, and i dunno, when you run out of water and have to go 6-7 days without it? Not all water passes through you in urine. I tend to drink a lot of water a day, thus I probably have a lot in reserve, so I could go 7 days without water. If you could only go 3, you probably dont drink enough water.