Abstract: A vacuum operated dental high volume evacuation system is provided wherein an extraction instrument is connected to a debris collector for solids which in turn is connected to a separator unit wherein the liquid in the evacuated material is separated from the vacuum air and the dry vacuum air is directed to the vacuum source unit which creates the vacuum for the system. The separator unit includes a vacuum chamber positioned above a drainage chamber with a valve disposed therebetween. The drainage chamber is normally maintained at atmospheric pressure and the valve is normally closed due to the pressure differential between the two chambers. A liquid level sensor is provided in the vacuum chamber to sense the rise of liquid therein which upon reaching a certain level trips the sensor which results in an equalization of vacuum pressure between the two chambers and the draining of the liquid in the vacuum chamber into the drainage chamber.