Your Samsung coffee maker has a descale mode that will remove any built up buildup of coffee residue. To activate this mode, first make sure your mug is empty, and then turn off the coffee maker by holding the 12 and 8oz buttons simultaneously for three seconds. Then, thoroughly rinse your reservoir and fill it with fresh clean water. Finally, press Brew to initiate the descale mode. After a few minutes, your machine will be rinsed and prepared for future use.