Air accumulations which occur particularly in pump outlets when water is delivered to pump outlets and pipe lines and makes water flow area narrower and causes decrease in capacity. Double ball vacuum lifters are used for preventing this adverse issue and in locations where high efficiency is required. Air which occurs when water is delivered to system firstly fills into vacuum lifter and discharged through holes which are located at inner side covers. Then water fills into vacuum lifter and lifts ball up and holes are closed and sealing is maintained.