A Keurig brewer may incompletely fill a cup if the exit needle is clogged with coffee grounds or cocoa, the machine needs to be descaled or the water reservoir is removed. Placing the reservoir back on the brewer and performing a cleansing brew is recommended if the reservoir is removed.
Descaling a Keurig brewer requires descaling solution, a large mug and fresh water. The Keurig Descaling Solution is run through the machine once and discarded. More descaling solution is placed in the machine and allowed to sit for at least 30 minutes. At least three fresh water rinses are required after descaling to ensure all of the solution has left the brewer.