NBN EN 13508-1:2003

This European Standard is applicable to the establishment of the condition of drain and sewer systems by inspection, status codification and consideration of external factors and other information.
It is applicable to drain and sewer systems, which operate essentially under gravity, from the point where the sewage leaves a building or roof drainage system, or enters a road gully, to the point where it is discharged into a treatment works or receiving water. Drains and sewers below buildings are included provided that they do not form part of the drainage system of the building.
This part of the standard specifies general requirements for the establishment of the condition of drain and sewer systems outside buildings.