EVS-EN 31:2011+A1:2014

This European Standard specifies the connecting dimensions of wash basins in accordance with EN 14688 regardless of materials used for their manufacture.
NOTE 1  Other connecting dimensions are permitted, e.g. special designs of wash basins, if the manufacturer supplies or recommends the appropriate fitting.
NOTE 2  The shape of the appliance in the figures is for illustration only; it in no way prejudices the final shape of the appliance, which is left to the initiative of the manufacturer.