evidence: Young babies under six months won’t usually need to have any water or extra drinks, other than their usual milk (NHS Choices, 2017). [...] Babies who are breastfed won't need water until they’re around six months old (NHS Choices, 2017). [...] Babies under six months should only drink tap water that has been boiled and cooled down. Water straight from the tap is not sterile so is not suitable for younger babies.