A tap for liquids dispenses liquids including wines from plastic bags or bladders packaged in cardboard boxes, and has three modes of operation. Liquids may be dispensed from the box on a shelf by manually turning a rotatable cap to open a valve for liquid to flow by gravity; an adapter attached to the tap automates the process and dispenses liquids through a pump; and the tap may be used to fill bags or bladders from an automated filling machine. In a first embodiment, the rotatable cap must be manually opened for both manual and automated operation. In a second embodiment, the rotatable cap may remain closed and the adapter can still dispense liquids through the tap using a pump.