Product description Liquid reagent Total Hardness I: content 20 ml for determining total hardness for the electronic pool water tester PoolLAB. Professional water analysis for private pools and hot tubs. To determine the total hardness, both reagents are required (I & II). The total hardness is the sum of calcium and magnesium ions dissolved in the water. The PoolLAB measures the total hardness in mg/l (ppm) CaCO3 (calcium carbonate). The value can be converted into German hardness (°dH) by multiplying it by the factor 0.056. The higher the total hardness, the greater the risk of water turbidity and limescale deposits. The higher the pH value in the water, the higher the risk of turbidity and limescale loss. For the total hardness measurement with the PoolLAB both liquid reagents are always required: Total Hardness I conditions the water sample e.g. Adjust the pH value of the water sample so that the reagent II can react correctly. Total Hardness II is the actual reagent, which causes the colour development necessary for the measurement process.