The hand-operated priming pump is designed to prime the centrifugal pump by evacuating air from the pump casing and suction line.  To prime a pump with a hand vacuum pump, close the discharge line throttling valve and spring-loaded check valve (if so equipped).  Make sure the drain cock in the bottom of the priming pump is closed.  Start the centrifugal pump, and operate the handle on the priming pump until liquid flows from the pump discharge.  After shutting down the pump, be sure to open the drain cock in the bottom of the hand primer and drain out any liquid in preparation for the next priming cycle, and to prevent damage in below freezing conditions.