How long do I need to sterilize my baby's bottles?

My son is almost 7 months old. We live in the country and have spring water. I buy water from the shop to give him, but I was wondering how long I need to keep sterilising his bottles?

The official recommendation is that you "disinfect" baby bottles for as long as you use them, but many families relax the process after a baby is 6 months old. Make sure the bottles are clean and free of soap residue. Wash them in a dishwasher (many have a special sanitising cycle, but that isn't necessary) or boil them for five minutes. Either of these approaches achieves the goal. Good washing is all that is needed for a household with a public water supply, but I recommend the dishwasher in all cases. Your spring water should meet government and local water quality standards for the whole family's health. If in doubt, ask your local public health department to check it. You will also want to know the fluoride content so your GP can prescribe the right amount of that supplement for your son.