1、As the built-in device generating electricity without the battery and any other power connets to water, LED will emit the light.  
2、When water flows down,the LED will light instantly and automatically by the water temperature;
A. When water temperature is ≤29℃, Green color will show automatically;
B. When water temperature is between 30℃～39℃, Blue color will show automatically;
C. When water temperature is above 40℃, Red color will show automatically;