We all want the very best when it comes to our babies’ nutrition. Whether you’re supplementing or exclusively formula-feeding, what goes into that bottle matters. The formula you choose is one part of the equation, but the quality of water it’s mixed with is just as important.

To help us to make the most informed decisions when it comes to what water to use, we turned to our panel of experts: Christopher Gavigan is the co-founder of The Honest Company; Dr. JJ Levenstein is our go-to pediatrician, and Dr. Maida Galvez is an Associate Professor of Preventive Medicine and Pediatrics at Mount Sinai’s Icahn School of Medicine. Suffice it to say, these three know what’s up. Here’s their take.

Know what’s coming out of your faucet. “Tap water from municipality to municipality can vary depending on many factors—original source, water treatment facility, local industry, and the microenvironment of pipes and plumbing delivering that water,” Dr. JJ says. While you likely already have an idea of what the water quality in your city is like, test it before giving it to your baby. The EPA’s Safe Drinking Water Hotline is a free public resource. “And if you’re on a private well, you should be testing your water at least once annually,” Gavigan says. Filter wisely. “If you have high-quality water, filtering is generally not necessary,” Dr. Galvez says. But if testing reveals contaminants to be present, check out NSF’s Contaminant Reduction Claims Guide for the best way to treat your specific contaminant. In addition to lead, cadmium, excessive chloramines (which are used as a disinfectant in water purification), arsenic, asbestos, mercury, and fungal spores can be cause for concern. Bottled isn’t always better. “Studies have found a wide range of potential contaminants in bottled water — and an estimated 25 percent or more of bottled water is simply tap water in a bottle,” Gavigan says, adding, “In many cases, tap water is more strictly regulated than bottled. Both are tested regularly for contaminants, but cities typically test much more often.” Dr. JJ also points out that “often, pallets of bottled water sit in warehouses with varying or little temperature control,” which can lead to the presence of chemicals. The bottom line. There’s no one size-fits all solution, as the experts agree, it really depends on the quality of the water where you live. To be safe, boiling water for 1-2 minutes before using it will kill germs. Just be careful to ensure that it’s cooled all the way through before use.