GAIRUI Investment Casting Screwed Check Valves is used to prevent back flow in the line .Flow is in a straight line through the valve resulting in minimal pressure drop . The disc swings into the open position as the media flows through the line .Back pressure in the line holds the disc in the closed position . GAIRUI Investment Casting Screwed Check Valves may be installed in horizontal or vertical lines ,but must be installed in proper relation to the media flow as indicated by the flow direction arrow marked on the body.