This International Standard specifies minimum requirements for water to be used in the preparation of concentrates, dialysis fluids for haemodialysis, haemodiafiltration and haemofiltration and for the reprocessing of haemodialysers. This International Standard does not address the operation of water treatment equipment nor the final mixing of treated water with concentrates to produce the dialysis fluids used in such therapies. That operation is the sole responsibility of dialysis professionals. This International Standard does not apply to dialysis fluid regenerating systems.