Water: fully breastfed babies don’t need any water until they’ve started eating solid food. Bottle-fed babies may need some extra water in hot weather. For babies under six months, use water from the mains tap in the kitchen that's been boiled then cooled. Water for babies over six months doesn’t need to be boiled. Bottled water is not recommended for making up infant formula feeds as it is not sterile and may contain too much salt (sodium) or sulphate. If you have to use bottled water to make up a feed, check the label to make sure the sodium (also written as Na) level is less than 200 milligrams (mg) per litre, and the sulphate (also written as SO or SO4) content is not higher than 250mg per litre. Bottled water is not sterile, so it will need to be boiled and cooled like tap water before you use it to prepare a feed.