Abstract: The present invention is directed to an improved purging of a liquid drain system for a liquid separator used in a moisture laden process vacuum system wherein the liquid separated from the flow stream by the separator is collected in an accumulator which in turn is periodically pressure purged to quickly remove the liquid contents of the accumulator while such accumulator is out of fluid communication with the liquid separator so that the vacuum process need not be interrupted. A pressure responsive drain valve is connected between the separator and the accumulator. The pressure used to purge the accumulator also activates the normally opened drain valve to inhibit the fluid flow between the separator and the accumulator. A pressure responsive drain is connected to the accumulator and opens in response to the increased pressure used to purge the accumulator and close the normally opened drain valve.