Water of the appropriate quality used in the preparation of dialysis fluid is an essential requirement of haemodialysis and related therapies. International standards have been developed to promote the installation of fit for purpose water treatment systems for haemodialysis and to safeguard the routine production of dialysis water suitable for use for haemodialysis and haemodiafiltration. The rationale for the development of these standards is to protect haemodialysis patients from adverse effects arising from known chemical and microbiological contaminants found in water and improperly prepared dialysis fluid.