amenity=drinking_water in a tight bounding box. OpenStreetMap tagging is messy. This V2 tool casts a much wider net:
drinking_water=yes (often attached to parks/restrooms)
amenity=water_point and man_made=water_tap
If this still doesn't hit ~172, then your 172 number likely came from a Metro Nashville Open Data dataset (like Metro Parks), not OpenStreetMap.