This European Standard is applicable to sodium dichloroisocyanurate, dihydrate used directly or used to prepare commercial formulations for disinfecting swimming pool water. It describes the characteristics of sodium dichloroisocyanurate, dehydrate and specifies the requirements and the corresponding test methods for sodium dichloroisocyanurate, dihydrate. It gives information on its use for treating swimming pool water. It also determines the rules relating to safe handling and use (see Annex B).