I have well water. and I also have a RO system.
Drinking Water Filters- Reverse Osmosis Water Purifiers & Water Softeners
so basically when you go to the store and get your jugs filled with water it is the same but they just filter City water.
My water is directly from a fresh water well.. even then I don't know what is in my water so I use the RO system to flush out what I don't want.
The only downside on this some say it wastes water by flushing out the bad components in the water. I just have it for my kitchen sink drinking water. Other use for water is treated through the water softener outside of my home.
beats the heck out of bottled water.