The Institute of Medicine states that most adult men need about 3.7 liters of water daily and women 2.7 liters. Water is best, but you can meet some of your water intake needs through other kinds of fluids as well as foods that have a high moisture content. Toddlers up to age 3 years, need about 1.3 liters daily, and between ages 4 and 8, roughly 1.7 liters is considered adequate intake. Boys between the ages of 9 and 18 need between 2.4 and 3.3 liters daily; girls in that age range need between 2.1 and 2.3 liters. Pregnant and nursing moms need 3 and 3.8 liters, respectively.