Great test kit to find out if and exactly how hard your water is, each drop is a grain (gr =17.1ppm Calcium/magnesium hardness) Used by the pros
https://tse1.mm.bing.net/th?&id=OVP.k0tZaR1gkHoiYSbtjaZ0swHgFo&w=330&h=186&c=7&pid=1.7&rs=1