The DPD method is elementary for the determination of chlorine and for the correct dosing of the water care product. The DPD No.1 tablet is used to determine the free chlorine. The tablet is placed in a cuvette with a few drops of the water sample and crushed, sample water is added and mixed by swirling. The value can be measured immediately. DPD No.1 is also used for the determination of bromine, ozone and monochloramine-dichloramine.