Dialysis water can be contaminated by chemical and microbiological factors, all of which are potentially hazardous to patients on haemodialysis. The quality of dialysis water has seen incremental improvements over the years, with advances in water preparation, monitoring and disinfection methods, and high standards are now readily achievable in clinical practice. Advances in dialysis membrane technology have refocused attention on water quality and its potential role in the bioincompatibility of haemodialysis circuits and adverse patient outcomes. The role of ultrapure dialysate is increasingly being advocated, given its proposed clinical benefits and relative ease of production as a result of the widespread use of reverse osmosis and ultrafiltration. Many of the issues pertaining to water quality in hospital-based dialysis units are also pertinent to haemodialysis in the home. Furthermore, an increased awareness of the environmental and financial consequences of home haemodialysis has resulted in the development of automated and more efficient dialysis machines. These new machines have an increased emphasis on water conservation and recycling along with a decreased need for a complex infrastructure for water purification and maintenance.