This 3 in 1 simple, colour test strip is a compact pool & spa water check test and allows you to test for the following parameters in your water: Total Alkalinity, Free Chlorine and pH, with the added bonus of Free Bromine testing too using the Free Chlorine pad. This allows you to test your water for simple maintenance. These test strips have a unique safety feature, which is called ‘bleach-out’ warning: if there is too much chlorine in the water they will go black. Other test systems may not show when chlorine levels are too high. Quite the opposite, when more chlorine is in the water than a test can measure for, the indication maybe ‘zero’ which can result in dangerously high levels of chlorine in the water. The ‘bleach-out’ warning stops this from happening and ensures high safety for pools and spas, and hence these test strips are preferred by industry professionals. Wide Test Range: Free Chlorine: 0, 0.5, 1, 3, 5, 10, 20 ppm Bromine: 0, 1, 2, 6, 10, 20, 40 ppm Total Alkalinity: 0, 40, 80, 120, 180, 240, 360 ppm PH: 6.0, 6.4, 6.8, 7.2, 7.6, 8.2, 9.0