Device for keeping water body in air pressure tank fresh

The invention discloses a device for keeping a water body in an air pressure tank fresh. The device comprises the air pressure tank and a bidirectional check valve; the air pressure tank comprises a tank body and an airbag; a water chamber is formed in the tank body, and the airbag is arranged in the tank body; an air chamber is formed in the airbag, and an inflation inlet communicating with the air chamber is formed in the tank body; a water in-out opening communicating with the water chamber is formed in the tank body; the bidirectional check valve comprises a main valve body; one end of themain valve body communicates with the water in-out opening, and the other end of the main valve body is used for communicating with a water supply pipe network; and a water inlet cavity and a water outlet cavity are formed in the main valve body, a water inlet cavity check valve is arranged in the water inlet cavity, and a water outlet check valve is arranged in the water outlet cavity. It is guaranteed that water in the