Hello everyone, I am trying to learn and understand the different color charts that are on the hth 6 way test strips box. I searched the web and found info on most of the ones listed i.e. Guideline values: (FC) Free chlorine: 0.5-1.5 ppm (mg/l) , pH figure is 7.2 – 7.6. (TA) Total Alkalinity 80 ppm and 120 ppm., & (CYA) Cyanuric acid:0-20 ppm (mg/l) however, the one on the top of the list which is TOTAL HARDNESS (TH) ppm. is a mystery. after searching the web I know it has something to do with the hardness of the water. but I can't find what the reading should be, i.e. 100 ppm or 200 pmm or ? can anyone help me. Thank you