Pregnancy & fertility

What water to use for baby formula

Tap, filtered, distilled, or bottled—what the research and paediatric guidelines actually say.

Aimee Devlin, founder of WaterHealthCheck

Aimee Devlin

Aimee Devlin · Certified Health Coach (IIN) · Founder, WaterHealthCheck · 11 min read · Updated June 2026

The short answer

For most U.S. households, properly prepared tap water is safe for formula. Whether to filter it depends on your specific utility's contaminant levels— particularly lead, nitrate, and TTHMs—not on tap water as a category. Distilled water is the safest default if you haven't checked your water yet. Bottled water is fine but unnecessary and expensive.

The quick decision guide

If: You haven't checked your tap water yet

Use distilled or fluoride-free bottled water while you check. Check your tap water with your ZIP code, then revisit.

If: Your tap water is within all EPA and EWG guidelines

Tap water is fine. No filter required for formula preparation. The American Academy of Pediatrics (AAP) supports tap water for formula when water quality is acceptable.

If: Your tap water has TTHMs, HAA5, nitrate, or lead above EWG guidelines

Use an NSF 53 certified carbon block filter for TTHMs/HAA5 and lead. For nitrate, use reverse osmosis (NSF 58) or distilled water. A Brita-type pitcher does not filter these contaminants.

If: Your home was built before 1986

Run the cold tap for 2 minutes before drawing water for formula, regardless of utility test results. Lead comes from household plumbing, not the treatment plant. And utility data won't catch it.

Check what's in your tap water first

Nitrate, TTHMs, lead, and PFAS—the four contaminants that affect formula water decisions—are tested and reported by your utility. Enter your ZIP to see your levels before deciding which water to use.

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Can you use tap water for baby formula?

Yes—with conditions. The American Academy of Pediatrics (AAP) states that tap water meeting EPA safety standards can be used to prepare infant formula. The CDC and WHO both support the same position for water systems complying with national standards.

The nuance: U.S. tap water meets legal EPA limits in the vast majority of systems, but EPA limits are set for general population safety and are not specifically calibrated for infants. The Environmental Working Group (EWG) publishes stricter health-based guidelines that reflect infant vulnerability— these are the thresholds worth checking.

The four contaminants that actually affect formula water decisions

LeadInfant concern

There is no safe level for lead in infants; it damages neurodevelopment at any detectable level. Even low levels of lead in the blood of children can result in behaviour and learning problems, lower IQ and hyperactivity, slowed growth, hearing problems, and anaemia. The risk is mostly in household plumbing (pre-1986 homes), not treatment plant water. A utility's "lead-safe" report does not mean your home's pipes are lead-free. EPA estimates that drinking water can make up more than 20 percent of a person's total exposure to lead. Infants raised on mostly mixed formula can receive 40 to 60 percent of their exposure to lead from drinking water.

→ If your home was built before 1986: flush the tap 2 min before drawing formula water. If also in doubt: use an NSF 53 filter or distilled water.

NitrateInfant concern

Nitrate can cause methemoglobinemia ("blue baby syndrome") in infants under 6 months by interfering with oxygen transport. The EPA MCL is 10 mg/L; EWG guideline is 0.14 mg/L. Nitrate in water is common in agricultural areas where heavy use of inorganic fertiliser and animal manure is common. Its high solubility means it passes through soil into the water table.

→ Standard carbon filters do not remove nitrate. Use reverse osmosis, distilled water, or nitrate-free bottled water if your utility reports nitrate above 1 mg/L.

Trihalomethanes (TTHMs) and haloacetic acids (HAA5)Infant concern

TTHMs and HAA5 are disinfection byproducts formed when chlorine reacts with organic matter. They're present in virtually all chlorinated tap water and raise developmental concerns at higher exposures. EWG health guidelines are much stricter than EPA MCLs.

→ NSF 53 certified carbon block filter reduces TTHMs effectively. Standard pitcher filters (Brita, PUR) are NSF 42 and reduce taste/odour but not TTHMs.

PFAS (PFOA, PFOS)Infant concern

Regulated since April 2024 at 4 ppt (EPA MCL). These manmade "forever chemicals" cross the placental barrier, pass through breast milk, and are common contaminants that build up and stay in the human body for many years. Associated with immune system effects and developmental concerns. Not present in all tap water—it depends on the industrial history near your water source.

→ Reverse osmosis (NSF 58) or activated carbon with NSF 53 certification where PFOA/PFOS is listed as a certified reduction claim. Standard pitcher filters do not remove PFAS reliably.

Do you need to boil tap water for formula?

In the U.S., boiling tap water for formula is no longer routinely recommended for healthy full-term infants by the AAP or CDC. Boiling addresses microbial contamination—which is rare in treated municipal water—but does not remove and actually concentrates chemical contaminants like lead, nitrate, and TTHMs (WHO, 2017; EPA guidance on lead in drinking water).

Boiling is appropriate when:

  • ·Your area has issued a boil-water advisory
  • ·Your infant is immunocompromised or premature (discuss with your paediatrician)
  • ·You are using well water (which may contain bacteria not present in treated tap water)

If you do boil: let the water cool to at least room temperature before mixing formula. Pouring hot formula can denature heat-sensitive nutrients.

Is distilled water safe for baby formula?

Yes. Distilled water is an appropriate choice for formula preparation. It contains no contaminants (including lead, nitrate, and PFAS) and is specifically recommended for households that haven't yet checked their tap water or where tap water quality is uncertain.

The only nuance: distilled water contains no fluoride. For infants in households without fluoridated tap water, paediatricians may recommend supplementation from 6 months; discuss with your paediatrician based on your water source and your child's caries risk.

On fluoride and infants: A 2024 National Toxicology Program (NTP) systematic review found moderate-confidence evidence linking higher fluoride exposures (above 1.5 mg/L, double the U.S. recommended level) to lower IQ in children. The NTP review was designed to evaluate total fluoride exposure from all sources and was not designed to evaluate the health effects of fluoridated drinking water alone. There was insufficient data to determine if the low fluoride level of 0.7 mg/L currently recommended for U.S. community water supplies harms children's IQ. This is a contested area; the science is evolving, and the formula-water decision (distilled vs. filtered tap) doesn't hinge on fluoride either way.

What filter actually works for formula water?

Not all filters are equal. NSF certification numbers tell you specifically what a filter removes:

Filter typeNSF standardTTHMs/HAA5PFASLeadNitrate
Pitcher (Brita, PUR)NSF 42✗✗✗✗
Under-sink carbon blockNSF 53✓✓ (if PFOA/PFOS listed as a claim)✓✗
Reverse osmosisNSF 58✓✓✓✓
Distilled (not a filter)—✓✓✓✓

⚠ Note on water ionizers (Kangen or similar)

The built-in FC1 carbon filter reduces chlorine, which helps limit disinfection byproduct formation, but does not remove TTHMs, HAA5, lead, nitrate, or PFAS. For formula preparation in areas where any of these contaminants exceed EWG guidelines, a dedicated NSF 53 certified carbon block filter (for TTHMs and lead) or NSF 58 certified reverse osmosis system (for nitrate and PFAS) is required alongside the ionizer. The ionizer does not substitute for certified filtration.

What about bottled water for formula?

Bottled water is an acceptable option, but it isn't the cleanest default. And it comes with a contaminant tradeoff the label won't tell you about.

Multiple studies have found that bottled water contains microplastics at higher concentrations than filtered tap water. Plastic bottles and caps shed microplastic particles into the water they contain, particularly when exposed to heat or UV light (Marfella et al., NEJM, 2024; WHO, 2019).

Microplastics in drinking water are currently unregulated in the US. The health research is early-stage—we don't have established causal evidence of harm at drinking water exposure levels—but from a precautionary standpoint, bottled water isn't the safer upgrade over tap that it's often assumed to be. The safer option if you want to avoid chemical contaminants and reduce microplastic exposure is reverse osmosis filtered tap water, not bottled.

If you're using bottled water anyway, look for:

  • ·NSF certification on the label. NSF is the only accredited product certification program that offers analysis for bottled water, including microbiological, chemical and radiological analyses.
  • ·Purified water is preferable to spring or mineral water. Labels reading "purified," "deionised," "demineralised," or "reverse osmosis processed" indicate the water has been treated to remove contaminants; unlike spring water, which is unprocessed and may contain variable mineral levels unsuitable for infant kidneys.
  • ·Low nitrate—the label should show <1 mg/L, especially for infants under 6 months.
  • ·"Nursery water" labelled products typically have fluoride at 0.7 mg/L—fine for infants over 6 months in consultation with your paediatrician.

Sparkling or mineral water is not appropriate for formula preparation—the mineral concentrations can be too high for infant kidneys.

Formula preparation with well water

Well water is not tested by the EPA or included in utility monitoring reports. If you use well water, the CDC and AAP both recommend testing before using it for infant formula, and annually after that.

At a minimum, test for: nitrate, coliform bacteria, lead, arsenic, and fluoride. Your local health department or a certified lab can run these tests for $50–200. Until you have test results, use distilled or certified bottled water for formula.

Step-by-step: formula water decisions

  1. 01

    Check your ZIP code

    See your utility's reported contaminant levels. Focus on lead, nitrate, TTHMs, HAA5, and PFAS. These are what determine whether your tap water is appropriate for formula, not tap water as a category.

  2. 02

    Check your home's age

    If built before 1986, flush the cold tap for 2 minutes before drawing formula water every time. This is independent of what your utility reports.

  3. 03

    Match the filter to what you found

    TTHMs/HAA5 → NSF 53 carbon block. Nitrate → reverse osmosis or distilled. Both → reverse osmosis. Nothing concerning → tap water is fine.

Frequently asked questions

What is the best water for baby formula?

Reverse osmosis filtered tap water or distilled water. Both remove lead, nitrate, PFAS, and TTHMs—the contaminants that matter most for infant formula preparation—and RO filtered tap water also has the lowest microplastic concentration of any common option. Bottled water is convenient but isn't the cleanest choice; it typically contains higher microplastic concentrations than filtered tap. If you haven't checked your tap water yet, distilled is the safest default while you do.

What water should I use for baby formula?

For most US households, tap water that has been checked and is within EWG guidelines is safe for formula. Distilled water is the safest default if you haven't checked your water yet. The contaminants that matter most for formula water are lead, nitrate, TTHMs, PFAS, and microplastics, not tap water as a category.

Can you use tap water for baby formula?

Yes, with conditions. The AAP supports tap water for formula when water quality is acceptable. Whether your specific tap water is acceptable depends on your utility's reported lead, nitrate, TTHM, and PFAS levels. Check your ZIP code before making a decision.

Is distilled water safe for baby formula?

Yes. Distilled water is an appropriate choice for formula preparation. It contains no contaminants, including lead, nitrate, and PFAS. On fluoride: distilled water contains none, and whether that matters is genuinely contested. A 2024 NTP systematic review found moderate-confidence evidence linking higher fluoride exposures to lower IQ in children, though at levels above what's in US tap water. Discuss your specific situation with your health provider rather than treating supplementation as automatic.

Do you need to boil tap water for baby formula?

Not routinely in the US for healthy full-term infants, per the AAP and CDC. Boiling addresses microbial contamination (rare in treated municipal water) but does not remove chemical contaminants and actually concentrates lead, nitrate, and TTHMs by reducing water volume.

What filter removes PFAS from baby formula water?

Reverse osmosis (NSF 58) is the most reliable option, removing PFAS consistently. An NSF 53 certified carbon block filter can also reduce PFAS, but only if PFOA/PFOS are specifically listed as a certified reduction claim on that product. The certification number alone isn't enough; check the product label. Standard pitcher filters (Brita, PUR) do not remove PFAS.

What filter removes nitrate from baby formula water?

Reverse osmosis (NSF 58 certified) and distillation both effectively remove nitrate. Standard carbon filters including Brita do not remove nitrate. This matters because nitrate can cause methemoglobinemia (blue baby syndrome) in infants under 6 months at elevated levels.

Can I use a Kangen machine or water ionizer for baby formula?

Yes, but only on the neutral 7.0 pH setting (labelled "clean water" on Enagic machines), not the alkaline drinking water setting (8.5–9.5 pH). At 7.0 pH, the water passes through the FC1 carbon filter without ionisation, producing neutral filtered tap water appropriate for formula preparation. Alkaline water should not be used for formula; it can interfere with the nutrient balance that formula is designed to deliver at neutral pH. The important caveat: in common water ionizers like Kangen machines, the internal filter removes chlorine but does not remove lead, nitrate, PFAS, or TTHMs. If your tap water has any of these contaminants above EWG guidelines, a dedicated NSF 53 certified carbon block filter (for lead and TTHMs) or NSF 58 reverse osmosis system (for nitrate and PFAS) is required upstream of the ionizer. Check your ZIP code first.

Can I use Brita water for baby formula?

A standard Brita pitcher is NSF 42 certified and does not remove lead, TTHMs, nitrate, or PFAS—the contaminants most relevant to formula safety. If any of these are present in your tap water above guideline levels, a Brita is not sufficient. Check your water first; if nothing concerning is found, tap water is fine.

Is bottled water safe for baby formula?

It's acceptable, but not the safest default. Bottled water avoids the tap water contaminants covered in this article, but multiple studies have found that bottled water contains microplastics at higher concentrations than filtered tap water. Plastic bottles and caps shed particles into the water, particularly when exposed to heat or UV light. From a microplastic standpoint, reverse osmosis filtered tap water is preferable to bottled. If you do use bottled water, look for NSF certified purified or reverse osmosis processed water, and check nitrate levels on the label (should be below 1 mg/L for infants under 6 months).

What bottled water is best for baby formula?

Look for bottled water labeled purified, deionised, or demineralised, or water processed through reverse osmosis. These contain low or no nitrate and no PFAS. Sparkling and mineral water are not appropriate for formula preparation. "Nursery water" with added fluoride at 0.7 mg/L is appropriate for infants over 6 months, but discuss fluoride with your health provider first; the science on fluoride and infant neurodevelopment is more contested than it was a few years ago.

Sources and methodology