Concealed water tank

The utility model discloses a concealed water tank. The concealed water tank comprises a tank body, a water tank protecting frame arranged on the tank body and a flushing face plate arranged inside the water tank protecting frame. The tank body is provided with a tank body water outlet. A water outlet pipe which is used for being connected with a toilet stool is connected to a tank body water outlet pipe. The tank body water outlet is provided with a seal ring and connected with the water outlet pipe through the seal ring. The seal ring comprises a first groove, a second groove and a curved-surface groove formed between the first groove and the second groove, wherein the first groove and the second groove are both of an annular shape, and the diameter of the first groove and the diameter of the second groove are both smaller than the diameter of the curved-surface groove. An installation groove matched with the seal ring in shape is formed in the inner wall of the tank body water outlet. The seal ring is embe