A liquid heating system comprising: (a) a reservoir (62, 162, 262); (b) a cold liquid supply (60, 160) communicating with the reservoir (62, 162, 262); (c) a heater (18, 118, 218) having an inlet connected to the reservoir (62, 162, 262) and an outlet (22, 122, 222) connected to one or more fixtures (72, 172, 272); (d) a heated liquid return connection (32, 232) connected between the outlet (22, 122, 222) of the heater (18, 118, 218) and the reservoir (62, 162, 262); (e) a pump (40, 140, 240) connected in series with the heater (18, 118, 218), whereby the pump (40, 140, 240) can draw liquid from the reservoir (62, 162, 262) and impel the liquid in a predetermined downstream direction through the heater (18, 118, 218) and through the return connection (32, 232) to the reservoir (62, 162, 262); (f) a controller (52, 152, 252) operable to actuate the heater (18, 118, 218) to supply heat to liquid passing from the inlet to the outlet (22, 122, 222) so as to bring the liquid at the outlet (22, 122, 222) to a setpoint temperature, the return connection (32, 232) and pump (40, 140, 240) being constructed and arranged to permit liquid flow from the outlet (22, 122, 222) of the heater (18, 118, 218) to the reservoir (62, 162, 262) but prevent liquid flow from the reservoir (62, 162, 262) to the fixtures (72, 172, 272) through the return connection (32, 232); and (g) either: (i) a temperature sensor (50, 250) operative to detect a temperature of liquid passing out of the heater (18, 118, 218), the controller being operative to deactivate the pump (40, 140, 240) and the heater (18, 118, 218) when the temperature detected by the sensor (50, 250) is at or approximates the setpoint temperature and the heater (18, 118, 218) is not supplying heat, or (ii) a temperature sensor operative to detect the temperature of liquid passing from the reservoir (62, 162, 262) to the heater (18, 118, 218), the controller being operative to deactivate the pump (40, 140, 240) and the heater (18, 118, 218) when the temperature detected by the sensor is at or approximates the setpoint temperature, characterized in that, the controller also being operative to reactivate the pump (40, 140, 240) after a period of deactivation regardless of the temperature detected by the sensor (50, 250), and then, responsive to the temperature detected by the sensor (50, 250), either (a) maintain the pump (40, 140, 240) in operation and activate the heater (18, 118, 218) or (b) deactivate the pump (40, 140, 240) again. (a) a reservoir (62, 162, 262); (b) a cold liquid supply (60, 160) communicating with the reservoir (62, 162, 262); (c) a heater (18, 118, 218) having an inlet connected to the reservoir (62, 162, 262) and an outlet (22, 122, 222) connected to one or more fixtures (72, 172, 272); (d) a heated liquid return connection (32, 232) connected between the outlet (22, 122, 222) of the heater (18, 118, 218) and the reservoir (62, 162, 262); (e) a pump (40, 140, 240) connected in series with the heater (18, 118, 218), whereby the pump (40, 140, 240) can draw liquid from the reservoir (62, 162, 262) and impel the liquid in a predetermined downstream direction through the heater (18, 118, 218) and through the return connection (32, 232) to the reservoir (62, 162, 262); (f) a controller (52, 152, 252) operable to actuate the heater (18, 118, 218) to supply heat to liquid passing from the inlet to the outlet (22, 122, 222) so as to bring the liquid at the outlet (22, 122, 222) to a setpoint temperature, the return connection (32, 232) and pump (40, 140, 240) being constructed and arranged to permit liquid flow from the outlet (22, 122, 222) of the heater (18, 118, 218) to the reservoir (62, 162, 262) but prevent liquid flow from the reservoir (62, 162, 262) to the fixtures (72, 172, 272) through the return connection (32, 232); and (g) either: (i) a temperature sensor (50, 250) operative to detect a temperature of liquid passing out of the heater (18, 118, 218), the controller being operative to deactivate the pump (40, 140, 240) and the heater (18, 118, 218) when the temperature detected by the sensor (50, 250) is at or approximates the setpoint temperature and the heater (18, 118, 218) is not supplying heat, or (ii) a temperature sensor operative to detect the temperature of liquid passing from the reservoir (62, 162, 262) to the heater (18, 118, 218), the controller being operative to deactivate the pump (40, 140, 240) and the heater (18, 118, 218) when the temperature detected by the sensor is at or approximates the setpoint temperature, (i) a temperature sensor (50, 250) operative to detect a temperature of liquid passing out of the heater (18, 118, 218), the controller being operative to deactivate the pump (40, 140, 240) and the heater (18, 118, 218) when the temperature detected by the sensor (50, 250) is at or approximates the setpoint temperature and the heater (18, 118, 218) is not supplying heat, or (ii) a temperature sensor operative to detect the temperature of liquid passing from the reservoir (62, 162, 262) to the heater (18, 118, 218), the controller being operative to deactivate the pump (40, 140, 240) and the heater (18, 118, 218) when the temperature detected by the sensor is at or approximates the setpoint temperature,