I've lived in two houses in the last 16 years and both had their own wells so we aren't on any city water source and don't have anything added to the water (floride or clorine). We live in an area where there are lots of limestone rocks so they probably filter the groundwater very well (our well is tested every other year to make sure it stays uncontaminated). None of my dogs have ever had tear staining so I guess the well water works very well for them (and us - it tastes so good compared to "city water").
Teresa