evidence: - Babies less than 6 months of age should not be given any extra water. Reason: regular formula is 85% water. Also, water can cause harm at this age. - Infants older than 6 months of age can have some extra water. Reason: water may be needed after starting solid foods or if weather is very hot. Safe at this age. - Limit water for infants age 6 to 12 months: don't give more than 4 ounces (120 mL) of extra water per day. On hot days, can give up to 8 ounces (240 mL) per day (AAP).