5-in-1 Water Enzymatic test strips semi-quantifies Nitrates (NO3), Nitrites (NO2), Total Hardness, Free Chlorine, and pH in water. Suitable for any type of water testing including CIP rinse water, water used in food & beverage processing (i.e. beer, juice, soft drinks, wine, soups, etc.), tap water, well water, fish farm water, farming, and more. One test strip is intended for testing a single water sample. The determination of total water hardness is based on a chemical reaction between an indicator dye – eriochrome black – with Ca2+ and Mg2+ cations, which causes a concentration-dependent change of color of the indicator dye.