Early warning: It is time to order a new filter/cartridge.
At 90% of the rated life of the filter/cartridge (based on time or water volume that has passed through the system), the monitor will sound an audible tone and a bar will flash whenever water is flowing. This reminds you to order a new filter/cartridge.
Second warning: It is time to replace the filter/cartridge.
At 100% of the rated life of the filter/cartridge, a different audible tone sounds, and the reminder bar turns red and flashes, telling you it is time to replace the filter/cartridge. You will never change the filter/cartridge prematurely or compromise your water quality by waiting too long.