A washstand assembly comprising a washstand having a water basin and a run-off opening, through which water to be discharged out of the water basin can be conducted away, wherein the run-off opening opens into an interior space of the washstand which, as seen in the direction of flow of the water, preferably has a greater cross section than the run-off opening, wherein the washstand has a rear wall with which the washstand, in the installation position, comes into contact with a building-side connection structure, and wherein, in the region of a rear wall of the washstand, the interior space is configured to be open, and an insert element having a run-off connector for connection to a building-side wastewater line, wherein the insert element is connected to the washstand in such a way that the interior space is tightly closed with respect to water, and that the water from the run-off opening can be fed to the run-off connector, wherein the run-off connector is arranged so as to be laterally offset with respect to the run-off opening, in particular in such a way that the run-off connector lies outside of a region which is formed by the clear width of the delimiting walls of the run-off opening in a viewing direction from the front side of the washstand in the direction of the interior space, wherein the run-off connector projects rearward away from the rear wall of the washstand and is in particular arranged in such a way that the run-off connector does not fall below or intersect a reference plane which extends at a right angle with respect to the rear wall and which extends through a lowermost edge of the rear wall, characterized in that the insert element has at least one sealing surface, on which there is arranged at least one seal element for interaction with the walls of the interior space and/or with the rear wall. a washstand having a water basin and a run-off opening, through which water to be discharged out of the water basin can be conducted away, wherein the run-off opening opens into an interior space of the washstand which, as seen in the direction of flow of the water, preferably has a greater cross section than the run-off opening, wherein the washstand has a rear wall with which the washstand, in the installation position, comes into contact with a building-side connection structure, and wherein, in the region of a rear wall of the washstand, the interior space is configured to be open, and an insert element having a run-off connector for connection to a building-side wastewater line, wherein the insert element is connected to the washstand in such a way that the interior space is tightly closed with respect to water, and that the water from the run-off opening can be fed to the run-off connector, wherein the run-off connector is arranged so as to be laterally offset with respect to the run-off opening, in particular in such a way that the run-off connector lies outside of a region which is formed by the clear width of the delimiting walls of the run-off opening in a viewing direction from the front side of the washstand in the direction of the interior space, wherein the run-off connector projects rearward away from the rear wall of the washstand and is in particular arranged in such a way that the run-off connector does not fall below or intersect a reference plane which extends at a right angle with respect to the rear wall and which extends through a lowermost edge of the rear wall, characterized in that the insert element has at least one sealing surface, on which there is arranged at least one seal element for interaction with the walls of the interior space and/or with the rear wall.