Abstract: A bottle capping and pressurizing device for capping and pressurizing a bottle containing an effervescent beverage, the bottle capping and pressurizing device including a housing member, the housing member substantially enclosing a chamber, a piston slidably within the chamber, an attachment apparatus for attaching the housing member to the bottle, the attachment apparatus including a capping surface for covering the mouth of the bottle, a passage leading from the interior of the chamber to the capping surface, and a one way flow valve for transferring air through the passage solely in a direction from the interior of the chamber to the capping surface, the one way flow valve including a flexible diaphragm overlaying the capping surface and at least one slit provided in the flexible diaphragm.