What Water Should I Use for Baby Formula?

Why water choice matters for infant formula

Infant formula is mixed with water at a ratio that makes the water itself a significant part of your baby\'s diet. A formula-fed newborn consumes roughly 25 ounces of mixed formula per day by the end of the first month, and most of that volume is water. The American Academy of Pediatrics (AAP) recommends using water that is safe and clean, but "safe" means different things depending on what contaminants are present in your local supply.

Babies are far more vulnerable to water contaminants than adults. Their smaller body weight means a given dose of a contaminant has a larger effect. Their organs are still developing, and their gut absorbs certain substances more readily. What would be a negligible exposure for an adult can be a meaningful exposure for a 7-pound newborn.

Contaminants that matter most for formula

Lead

The EPA action level for lead is 15 ppb, but the AAP and CDC agree there is no safe level for infants. Lead damages the developing brain and nervous system. It enters water from home plumbing, not from the water source itself, so your city\'s water report may not reflect what comes out of your tap. Homes built before 1986 are at highest risk. Always run cold water for 30 seconds before using it for formula if you have not filtered it. Learn more about lead in tap water.

Nitrate

The EPA maximum contaminant level for nitrate is 10 mg/L. Above this level, nitrate causes methemoglobinemia ("blue baby syndrome"), a condition where the blood cannot carry oxygen effectively. Infants under 6 months are most susceptible because their stomach acid is lower, which allows bacteria to convert nitrate to nitrite more efficiently. Agricultural areas with heavy fertilizer use are most likely to have elevated nitrate.

Fluoride

The CDC recommends a fluoride level of 0.7 mg/L for community water systems to prevent tooth decay. However, mixing formula with fluoridated water can expose infants to more fluoride than intended, potentially causing mild dental fluorosis (white spots on developing teeth). The AAP notes this is a cosmetic concern, not a health emergency, but parents who want to minimize fluoride exposure can use low-fluoride bottled water or reverse osmosis filtered water.

PFAS

The EPA set maximum contaminant levels for PFOS and PFOA at 4 parts per trillion in 2024. PFAS exposure in infants is linked to immune system effects and reduced vaccine response. Many water systems still exceed these limits. Learn about PFAS in drinking water.

Bacteria

Formula is not sterile, and neither is most tap water. The CDC recommends preparing formula with water heated to at least 158F (70C) if your baby is under 3 months, was born premature, or has a weakened immune system. For healthy, full-term infants over 3 months, room temperature water that meets EPA standards is generally considered safe.

Water sources ranked for formula safety

Water source	Lead	Nitrate	Fluoride	PFAS	Bacteria	Overall
Reverse osmosis filtered tap	Removed	Removed	Removed	Removed	Removed	Best
Distilled or purified bottled	None	None	None	Varies	Low risk	Very good
Nursery water (commercial)	None	None	Low or none	Varies	Low risk	Good
Carbon filtered tap (NSF 53)	Removed	Not removed	Not removed	Most removed	Not removed	Good for lead/PFAS
Tested, safe tap water	Varies	Varies	0.7 mg/L typical	Varies	Low risk	Acceptable
Standard pitcher filter	Not removed	Not removed	Not removed	Not removed	Not removed	Minimal benefit
Untested well water	Unknown	Unknown	Unknown	Unknown	Unknown	Avoid
Sodium softened water	Varies	Varies	Varies	Varies	Low risk	Avoid (high sodium)

Step-by-step: preparing formula safely

1. Know your water. Check your city\'s water data on CheckMyTap to see lead, PFAS, nitrate, and fluoride levels before choosing a water source.
2. Use cold water only. Hot tap water dissolves more lead and metals from pipes. Start with cold water and heat it afterward if needed.
3. Flush the tap. Run cold water for 30 seconds to 2 minutes if the tap has not been used for several hours. This clears water that has been sitting in contact with plumbing.
4. Filter if needed. If your city has known lead, PFAS, or nitrate issues, use an appropriate filter. An under-sink reverse osmosis system provides the broadest protection.
5. Heat if recommended. For high-risk infants (premature, under 3 months, immunocompromised), the CDC recommends heating water to 158F (70C) before mixing with formula to reduce bacterial risk.
6. Mix and cool. Add formula powder to the heated water, mix thoroughly, and cool to body temperature (98.6F / 37C) before feeding. Test on your wrist.

Boiling is not enough

Boiling water kills bacteria and parasites effectively. It does not remove lead, PFAS, nitrate, fluoride, or any chemical contaminant. In fact, boiling concentrates these chemicals because some water evaporates while the contaminants remain. If your concern is chemical contamination rather than biological contamination, you need filtration, not boiling.

Water softeners and formula

Salt-based water softeners replace calcium and magnesium with sodium. This adds sodium to your water, which is not recommended for infants. The sodium content depends on your water\'s original hardness: at 15 grains per gallon hardness, a softener adds roughly 120 mg/L of sodium. For formula preparation, bypass the softener and use unsoftened, filtered cold water. Most softeners have a bypass valve, or you can install a separate unsoftened line to the kitchen cold tap. Learn more about water softener setup.

When to use bottled water

Bottled water labeled "purified" or "distilled" is a safe option for formula. Avoid bottled water labeled "spring" or "mineral" unless you can verify the mineral content. Avoid bottled water with added fluoride if you want to minimize fluoride exposure. Note that bottled water is not tested as frequently as municipal tap water. The FDA requires annual testing for bottled water, while the EPA requires municipal systems to test hundreds of times per month.

Related resources

• Water quality during pregnancy
• Lead in drinking water
• PFAS (forever chemicals) explained
• Under-sink filter guide
• Check your city\'s water quality