This document specifies the minimum chemical and microbiological quality requirements, for water used for preparation of dialysis fluids, concentrates, and for the reprocessing of haemodialysers, together with the necessary steps to ensure conformity with the requirements. The document also provides guidance for the ongoing monitoring of the purity of such water in terms of chemical and microbiological quality. This document is applicable to — water used in the preparation of dialysis fluids for haemodialysis, haemodiafiltration and haemofiltration and the reprocessing of haemodialysers, and — water used in the preparation of concentrates. This document does not apply to dialysis fluid regenerating systems. The operation of water treatment equipment and the final mixing of treated water with concentrates to produce dialysis fluid are the sole responsibility of dialysis professionals.