text: how much water should a person with a bmi of 43 drink daily? 5'10" 315 lbs.  someone told me if my blood volume is not at optimum level, that my kidneys have to work in reverse.  can you tell me signs of dehydration and use some scare tactics on why i need to drink water.  is tap water ok?  distilled?  well? holy? 64 ounces. this is the recommended amount for everyone. tap, distilled, spring, it doesn't matter. drink whatever water you like. personally i drink deja blue.