A tap is described, for delivering liquids from a vessel comprising: an elongated supporting body equipped with an inclined internal contact surface next to its delivery end; an upper closing element and tamper-preventing seal which closes the delivery end of the supporting body; a pin centrally placed inside the supporting body and equipped with an O-ring adapted to sealingly engage the inclined internal contact surface when the tap is closed; a dome-shaped elastic valve element operatively connected to the pin at the opposite end with respect to the delivery end of the supporting body, the dome-shaped elastic valve element performing the automatic closure of the tap; and a plate operatively connected to the dome-shaped elastic valve element.