Remove the reagent KW-15 from test vial. Fill the vial to the 10 ml line with water sample. Add drops of KW-15 one at a time mixing between each addition. Count the number of drops required for the colour to change from red/purple to pure blue.
Hardness = Drops KW-15 used x 20 (10 DROPS = 200 PPM CaCO3)
In SOFT WATER areas use a 20 ml sample. Hardness = Drops KW-15 used x 10 (10 DROPS = 100 PPM CaCO3)