Abstract: A beverage container pressurizer and more particularly to a screw threaded cap that replaces the screw threaded cap normally provided on large beverage containers and a manually operated reciprocating piston-type pump sealingly and releaseably connected with the screw threaded cap for pressurizing the beverage container to keep the carbonation suspended in a liquid state for sustaining the quality of a carbonated beverage for an extended life before "going flat". The replacement cap includes a valve assembly which permits entry of pressurized air from the pump but prevents egress of pressurized air from the container when the pump is removed. This arrangement enables a single pump to pressurize a number of beverage containers since the pump is separable from the replacement screw threaded cap which remains with the beverage container until all of the beverage has been consumed.