Abstract: Plunger sealing and lubricating apparatus for horizontal plunger pumps including a front sealing packing and the front half of a back sealing packing lubricated with water which is provided from the suction chamber and leaks from the front sealing packing. The back half of the back sealing being lubricated with oil provided by the oiling packing behind the back sealing packing. The back sealing packing acts as a water-tight barrier and makes such a wide frictional contact with the plunger to prevent water from leaking. Thus, resulting in the return of water to the suction chamber from a space between the front and back sealing packings through a passage connecting the space with the suction chamber. By the use of the apparatus, a secondary liquid line can be introduced to the suction side of the pump to which the main liquid line is connected.