How much water should a 57 year old male drink per day?

57 year and water: You do not give enough information to get an informed answer. Do you have any cardiac or kidney disease? Are you on any diuretic, or other, medication? If the answers to the questions are "no", then you drink when you are thirsty. Weighing yourself daily can tell if you are retaining fluid, as fluid accumulation increases you weight daily. If you continue to gain weight, you are retaining water.