A tempered hot water delivery system configured to prevent or reduce colonisation of Legionella bacteria in tempered water delivered from the system to one or more outlets in a facility. The system comprises: a thermostatic mixing valve comprising; a hot water inlet for connection to a supply of hot water at a temperature of at least 60° C., a cold water inlet for connection to a supply of cold water, a tempered water outlet for supplying tempered water obtained from mixing the supplied hot water and cold water to provide tempered water at a temperature of between 36° C. to about 53° C. to at least one tempered water outlet of a facility, a recirculating inlet for connection to a recirculating water line circuit; and a recirculating water line circuit comprising a circulating return line connected to a circulating return outlet from the facility and to a water inlet feed line for connection to an inlet of a water heater and storage tank for providing the supply of hot water, the recirculating water line circuit further comprising a thermostatic element configured to introduce hot water to the recirculating water line circuit to maintain the temperature of water in the recirculating water line circuit during periods of little or no draw-off.