A beverage system includes a pump that draws a set amount of a flavored concentrate into a mixing chamber for mixing with water to form a beverage. A locking ring attaches an adapter plate to a pump head. When the locking ring is in a locked position, a magnet of the locking ring is detected by a reed switch. If the locking ring rotates from the locked position, the reed switch does not detect the magnet, indicating that the locking ring, and therefore the pump head, is incorrectly or not completely installed. The controller then stops operation of the pump.