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 (F) 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 (R) 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 (F) 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 (R) 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 . <EOS>