Meh, I’ll take a pass on that. Chlorinated tap water in developed nations should have no appreciable microbial content. If you’re concerned about lead, I can understand that. If your goal is sterile food and your baby is healthy, I don’t really get that. You’re presumably washing your baby’s bottles in tap water anyway.
https://www.cdc.gov/fluoridation/faqs/infant-formula.html
>Can I use flouridated tap water to mix formula? "Yes, you can use fluoridated water for preparing infant formula. However, if your child is only consuming infant formula mixed with fluoridated water, there may be an increased chance for mild dental fluorosis. To lessen this chance, parents can use low-fluoride bottled water some of the time to mix infant formula; these bottled waters are labeled as de-ionized, purified, demineralized, or distilled, and without any fluoride added after purification treatment. The U.S. Food and Drug Administration (FDA) requires the label to indicate when fluoride is added."
Plus even ignoring heavy metal content, in some areas there might be micro-organisms in tap water (since it is sourced from a natural well or similar), so you'd need to be boiling tap water or risk making a newborn sick (even if your body could easily cope with similar water).
> Talk to your baby’s pediatrician and ask what kind of water you should use when mixing infant formula. The American Academy of Pediatrics (AAP) recommends boiling water to remove impurities and kill germs. While most municipal and public drinking water supplies are required to follow strict regulatory guidelines to be safe, pediatricians generally still suggest using boiled water to mix infant formula, at least for the first three or four months. Since there is no evidence that bottled water is safer than municipal water sources, the AAP says that while parents can use bottled water to mix formula, it needs to be boiled first. You can also use distilled water that has already been purified or ready-to-use formulas, which do not need to be mixed with water.