This function is used to clean and sterilize the inner tubes and networks, pipes. To activate, hold down the drum cleaner button for about 5 seconds. During this process, the heating and cooling functions stop working. The hot water digital display will turn on the indicator light. During this process do not use the unit. It is recommended to use this function at night, especially after the children and the elderly are away. After the 75-minute cleaning process is complete, it will continue with the 75-minute cooling process and after that, the unit will return to normal. If you want to exit this program before the cleaning process and/or the cooling process is complete, press and hold the tube cleaning program button for about 5 seconds.