This study aims to investigate whether hot water systems supplied with harvested rainwater present an increased risk to health over hot water systems supplied with potable mains water. It reviews previous studies investigating the health effects of utilising rainwater within domestic systems. The main risk to public health of mains-supplied hot water systems is the operation, maintenance, age, location and temperature of the system. Rainwater-harvesting systems contain an inherent water treatment train consisting of flocculation, settlement …