There are various opinions on how much water we supposed to drink a day but The health authorities commonly recommend eight 8-ounce glasses, which equals about 2 liters, or half a gallon. Research shows people who gulp a glass of H2O, when they’re thirsty get enough to stay healthy and hydrated. Water-rich foods like soup, fruit, and vegetables and drinks like juice, tea, and coffee all help you get your fill. You might need to drink more water if your urine is dark yellow, you don’t go regularly, you're very active, or you live in a hot climate.