Water heating by a domestic water heater. Two conflicting safety issues affect water heater temperature—the risk of scalding from excessively hot water greater than , and the risk of incubating bacteria colonies, particularly "Legionella", in water that is not hot enough to kill them. Both risks are potentially life-threatening and are balanced by setting the water heater's thermostat to . The European Guidelines for Control and Prevention of Travel Associated Legionnaires’ Disease recommend that hot water should be stored at and distributed so that a temperature of at least and preferably is achieved within one minute at points of use. If there
Water supply and sanitation in Gibraltar that sea water and sewage had infiltrated the town's supply of drinking water. The findings led to the old Spanish aqueduct and wells being closed down permanently as it was realised that they posed a severe hazard to public health. Another cholera outbreak in 1865, which killed several hundred people, prompted the establishment of a Sanitary Commission for Gibraltar. Ironically, the fragmented water provision system in Gibraltar probably hindered the spread of the outbreak as it isolated the contaminated water supplies. Inhabitants who drew their water from private wells or cisterns were far less likely to succumb to the disease