Water-sealed liquid ring vacuum pump systems are well known for its reputation for extraordinary reliability, extremely long field-proven records and low maintenance. But it needs continuous supply of water while running, which becomes expensive when water and sewage costs are added to it. Field selectable and adjustable quantity of partial water is re-circulated up to 95% without using heat exchangers and chilled water. Operating costs are reduced dramatically with this feature without adding any cost to the basic price, installation and maintenance.