Desalted water tank

The desalting water tank comprises a tank body, a breathing pipe and an overflow pipe, the tank body is provided with an inner cavity, the breathing pipe is arranged at the upper end of the tank body and communicated with the inner cavity, the first end of the overflow pipe extends into the upper end of the inner cavity, the second end of the overflow pipe extends out of the tank body and extends downwards, and the second end of the overflow pipe is provided with an air pollution prevention device; the air pollution prevention device comprises a support, a sealing piece and a sealing gasket, the support is provided with a first through cavity, the sealing piece is arranged on the support and provided with a second through cavity, the first through cavity and the second through cavity are communicated to form a circulation channel, and the sealing gasket is rotatably installed on the sealing piece to cut off or conduct the circulation channel. The air pollution prevention device can block air circulation insid