A residential building having a plumbing system comprising: a closed recirculating hot water line (104, 106), having a pump system to promptly provide hot water at every tap, following lengthy periods of nonuse, the pump system having a motor of up to 0.5 horsepower (372,5 W) or one drawing up to 6 A of current, the pump system comprising: an external controller to control the timed operation of said pump system, said external controller comprising: a programmable external power controller unit comprising a closed outer shell, an electrical power connection for removably connecting to an external power supply, and a programmable microcontroller for controlling the use of power received from the external power supply; and an electrical conductor connection designed to connect with said pump system to provide power in accordance with the program on the programmable microcontroller within the closed outer shell of the controller unit; a temperature sensor connected to the microcontroller being placed within the recirculating hot water line upstream from the pump, the microcontroller receiving data electronically from the temperature sensor for sensing a temperature change indicating the flow of hot water through the hot water line; a time clock, a database for receiving, logging and recording data signals from the temperature sensor indicating the times when a flow of hot water occurred during a pre-defined data logging time period, and a software algorithm in the microcontroller for instructing the microcontroller to operate the water pump mechanism at predetermined times based upon the previously logged and recorded data signals, said water pump mechanism being operationally controlled by the microcontroller, in accordance with the logged and recorded hot water flow times in the data pattern generated from occurrences of hot water flows logged by the microcontroller during the immediately prior pre-defined data logging time period, the water pump mechanism operating to recirculate hot water through the hot water system in accordance with the logged and recorded data pattern generated during each pre-defined data logging time period in order to update the logged usage pattern data on an ongoing basis, and the micro-controller receiving logging and recording data signals during each successive pre-defined data logging time period for the next successive time period from the temperature sensor. a closed recirculating hot water line (104, 106), having a pump system to promptly provide hot water at every tap, following lengthy periods of nonuse, the pump system having a motor of up to 0.5 horsepower (372,5 W) or one drawing up to 6 A of current, the pump system comprising: an external controller to control the timed operation of said pump system, said external controller comprising: a programmable external power controller unit comprising a closed outer shell, an electrical power connection for removably connecting to an external power supply, and a programmable microcontroller for controlling the use of power received from the external power supply; and an electrical conductor connection designed to connect with said pump system to provide power in accordance with the program on the programmable microcontroller within the closed outer shell of the controller unit; a temperature sensor connected to the microcontroller being placed within the recirculating hot water line upstream from the pump, the microcontroller receiving data electronically from the temperature sensor for sensing a temperature change indicating the flow of hot water through the hot water line; a time clock, a database for receiving, logging and recording data signals from the temperature sensor indicating the times when a flow of hot water occurred during a pre-defined data logging time period, and a programmable external power controller unit comprising a closed outer shell, an electrical power connection for removably connecting to an external power supply, and a programmable microcontroller for controlling the use of power received from the external power supply; and an electrical conductor connection designed to connect with said pump system to provide power in accordance with the program on the programmable microcontroller within the closed outer shell of the controller unit; a temperature sensor connected to the microcontroller being placed within the recirculating hot water line upstream from the pump, the microcontroller receiving data electronically from the temperature sensor for sensing a temperature change indicating the flow of hot water through the hot water line; a time clock, a database for receiving, logging and recording data signals from the temperature sensor indicating the times when a flow of hot water occurred during a pre-defined data logging time period, and said water pump mechanism being operationally controlled by the microcontroller, in accordance with the logged and recorded hot water flow times in the data pattern generated from occurrences of hot water flows logged by the microcontroller during the immediately prior pre-defined data logging time period, the water pump mechanism operating to recirculate hot water through the hot water system in accordance with the logged and recorded data pattern generated during each pre-defined data logging time period in order to update the logged usage pattern data on an ongoing basis, and the micro-controller receiving logging and recording data signals during each successive pre-defined data logging time period for the next successive time period from the temperature sensor.