Babies up to one year
If babies are on breastfeeding and get enough milk, it is OK not to give them water at all until they are 6-7 months, and start giving it at the same time with dietary supplements. The mother's body perfectly adapts to the needs of the child, and it gets enough liquid with milk.
On a bottle-feeding babies also get liquid contained in mixtures, and the need for pure water occurs not earlier than at the age of 3-4 months, usually even later. However, even a very small baby can receive some water in case of constipation, hiccups or rises of temperature. It is crucial that it should be special water for babies only.
The diet of a toddler is completely (or almost) composed of solid food, and water is needed for normal digestion. In addition, during this period, children become restless and move a lot, which also increases their need for water. The average norm for children of 1-3 years is 50 ml per 1 kg of body weight.
At this age, the nervous and locomotor systems are actively developing, and therefore the child needs large amounts of calcium, fluoride and magnesium. For its full fixationit is better to get it not only from food but also from water, so you can buy non-carbonated mineral water to your place and make sure your baby always has access to it. The need is 1.2-1.7 liters a day, depending on the weight and the level of activity.
7 years and older
Gradeschoolers need water in amounts that can reach 2.5 liters per day, which is even greater than that of some adults. The more children are, the more they need to drink. Teach the child to a healthy drinking schedule and do not give much soda or juice, as it is better for the health of children to get used to quenching thirst just with water, not with sweet drinks. Give them water to school and let them grab it for a walk.