Tap water is usually surface water (from rivers) or groundwater (from wells). Both get processed. But bottled "purified water" is just tap water that’s been run through extra filters. Marketing genius, huh?
"Spring water" comes from an actual underground source and is barely treated. It’s basically the same stuff, just with a prettier label and a 50x markup.
Honestly, your tap water is more regulated than bottled water. The EPA is stricter than the FDA on this. So unless your pipes are made of lead, tap is a win.