Distilled water is water that has been boiled into steam and then condensed back into liquid, removing up to 99.5% of impurities. For babies, it’s most commonly used to mix infant formula, since it’s free of contaminants like lead, nitrates, bacteria, and excess minerals that can sometimes be present in tap water. It also contains no fluoride, which matters for infant dental health in ways that might surprise you.
How Distilled Water Differs From Tap Water
The distillation process strips out nearly everything that isn’t pure water. That includes dissolved minerals like calcium, magnesium, and iron, as well as potentially harmful substances like lead, chlorine, nitrates, and organic compounds. It also inactivates bacteria, viruses, and parasites. The result is about as close to pure H₂O as you can get outside a laboratory.
Tap water, by contrast, contains trace minerals and is typically treated with chlorine or chloramines to kill germs. In most U.S. communities, tap water also contains added fluoride to support dental health. The quality of tap water varies by location, and older plumbing can introduce lead or other metals that aren’t in the water when it leaves the treatment plant.
Why Parents Use It for Formula
Many pediatricians recommend distilled water for mixing powdered or concentrated liquid formula because it offers a clean, consistent baseline. You don’t have to worry about what’s in your local water supply, whether your pipes are old, or whether contaminant levels have spiked after a storm. It’s a simple way to reduce variables when preparing something your baby will consume multiple times a day.
That said, the American Academy of Pediatrics notes that tap water is generally safe for formula preparation unless there’s a known contamination issue in your area. For babies under two months, premature infants, or those with weakened immune systems, the AAP recommends boiling water first and letting it cool for about five minutes before mixing formula, regardless of the water source. This is worth noting because distilled water, while very pure, is not guaranteed to be sterile once it’s been bottled and sitting on a shelf. Certain microorganisms can grow even in nutrient-poor distilled water over time.
The Fluoride Question
One of the biggest practical differences between distilled water and tap water for babies is fluoride. Most municipal tap water in the U.S. contains fluoride, which strengthens developing teeth but can also cause dental fluorosis, a cosmetic discoloration of tooth enamel, when infants are exposed to too much of it during tooth development. Formula-fed babies are at higher risk for fluorosis than breastfed babies because they consume larger volumes of water daily through their formula.
Using distilled water eliminates fluoride from the equation almost entirely. The AAP suggests a balanced approach: primarily use fluoridated tap water for formula, but occasionally rotate in non-fluoridated water (like distilled or certain bottled waters) to keep total fluoride intake moderate. If your tap water has especially high fluoride levels, leaning more heavily on distilled water for formula may make sense. Your pediatrician can help you gauge this based on your local water report.
Plain Water and Babies Under Six Months
Whether it’s distilled, filtered, or straight from the tap, babies under six months old should not be given plain water to drink. Breast milk and formula already provide all the hydration an infant needs. Giving extra water, even pure distilled water, can dilute sodium levels in the blood to dangerously low concentrations, a condition called water intoxication.
In infants, water intoxication can cause vomiting, facial puffiness, irritability, and in serious cases, seizures. It happens because a baby’s kidneys are still immature and can’t flush excess water the way an adult’s can. The same risk applies if formula is over-diluted with too much water, which is why following the mixing instructions on the formula container exactly is important. Once babies start solid foods around six months, small sips of water with meals are generally fine.
Choosing the Right Water for Your Situation
For most families with safe municipal water, tap water works well for formula. If you’re unsure about your water quality, if you have a well, or if your home has older plumbing, distilled water is a reliable alternative that removes the guesswork. It’s widely available at grocery stores and is inexpensive.
A few practical tips to keep in mind:
- Check the label. Make sure the bottle says “distilled” rather than “purified” or “spring water,” which go through different processes and may still contain minerals or fluoride.
- Use it promptly. Once opened, store distilled water in the refrigerator and use it within a day or two for formula preparation.
- Don’t assume it’s sterile. For premature babies or those with compromised immune systems, boil even distilled water before mixing formula, then cool it to a safe temperature.
- Follow formula ratios exactly. The type of water matters less than using the correct amount. Too much water of any kind is a safety risk for young infants.
Distilled water isn’t nutritionally better or worse for babies than properly treated tap water. Its advantage is predictability: you know exactly what’s not in it. For parents navigating formula feeding, that consistency can offer real peace of mind.