System and method for efficient and expedient delivery of hot water

A fluid demand detection device comprising:

• a pipe for transporting a fluid;
• a sensor for sensing a temperature that varies with the temperature of the fluid;
• a processor in signal communication with the temperature sensor and a time base;
• the processor for making a plurality of temperature measurements corresponding to different times and for calculating at least one temperature difference between a first temperature measured at a first time and one or more second temperatures measured at one or more respective second times subsequent to said first time;
• each of the times bounded by a single preselected time interval;
• and,
• the processor for causing an electrical current to flow in an electric circuit when one of said temperature differences as compared to a respective trigger value indicates that fluid has been demanded from the pipe.

A method of detecting hot water demand comprising the steps of:

• transporting hot water in a first pipe in fluid communication with a potable hot water source and a hot water valve;
• measuring a plurality of temperatures corresponding to different times with an infrared temperature sensor in signal communication with a processor said temperatures being measured at a location on an outer surface of a second pipe transporting cold water to the hot water source;
• varying the temperature of the location on the outer surface of the second pipe by opening and closing the valve;
• calculating a time rate of temperature change;
• and,
• signaling a recirculating pump to transport water from the first pipe to the hot water source when the time rate of temperature change exceeds a preselected trigger value.