While it is good to stay hydrated, it is harmful to drink extreme amounts of water. You should generally not drink more than 12 quarts (48 cups) in a 24-hour period. If higher amounts of fluid replacement are needed due to prolonged work in high heat conditions, a more inclusive heat illness prevention program may be needed. Typically, you should frequently drink small amounts of water before becoming thirsty to maintain good hydration. During moderate activity, in moderately hot conditions, you should drink about 1 cup every 15 to 20 minutes.