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 an  automatically;
A,When water temperature is ≤32℃,Green color will show automatically ;   
B,When water temperature is between 33℃-41℃,Blue color will show automatically;    
C,When water temperature is between 42℃-45℃,Red color will show automatically;    
D,When water temperature is above 46℃,Red color will flash immediately.    
3. This item will change its color by detecting water temperature.