The 3 Pad Pool test strip monitors 3 different variables vital to swimming pool health: pH, Chlorine (0 – 5ppm), and Alkalinity. The pH pad detects a range of 6.8 to 8.0, while the Alkalinity pad is calibrated at 0, 1, 40, 80, 150, and 200ppm. The Chlorine pad is for low levels of Chlorine and is calibrated at 0, 1, 3, 5, & 10ppm. The special pH test pad is designed for low-ionic and low-buffered waters present in pools.