Can I make formula with tap water?

What the evidence says

For most families, ordinary cold tap water is a safe choice for mixing powdered or concentrated infant formula, as long as your municipal water supply is considered safe to drink. Health Canada notes that municipal tap water and most bottled water (except carbonated or mineral water) work well, and recommends using cold tap water rather than hot, since hot tap water can pick up more metals like lead from household pipes.

For most healthy, full-term babies over 2 months old, water at room temperature is fine. However, Health Canada and the CDC both note that powdered formula isn't sterile, so for babies under 2 months old, born prematurely, or with a weakened immune system, it's safer to boil the water, let it cool to about 70°C (roughly 30 minutes of cooling, or use a thermometer), then mix the formula, cooling further before feeding to protect against a rare but serious bacteria called Cronobacter.

If you're unsure about your tap water's safety (for example, if you're on a private well, there's a boil-water advisory, or you notice unusual taste, smell or color), contact your local health department or water utility before using it, and consider bottled water in the meantime.

One more safety note unrelated to bacteria: never add extra water to try to stretch formula or make it 'go further.' Diluting formula this way can cause dangerous drops in your baby's sodium levels and has led to serious illness.