When we talk about total temporary hardness we mean the total calcium carbonate and magnesium carbonate present
3 drops of reagent into 10mL of the town water supply in Auckland produces a colour change. Each drop represents 1 grain per gallon of total temporary hardness, or 17.1mg/L (ppm). So 3 drops = 51.3mg/L. that in my book is as close to perfect as you can get
So, if you are connected to the town water supply in Auckland all you need in the way of water treatment is a carbon filter, which is inexpensive, to take out the chlorine, which is noticeable.