This European Standard is applicable to the investigation and assessment of drain and sewer systems outside buildings. It is applicable to drain and sewer systems, which operate essentially under gravity, from the point where the wastewater 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 European Standard specifies a coding system for the description of the internal condition of drains, sewers, manholes and inspection chambers identified through visual inspection. Where appropriate, it can also be used for pressure and vacuum systems in accordance with the requirements of the employing authority. Visual inspection of drain and sewer systems can be carried out as part of the investigation in order to undertake the assessment. This part of the European Standard does not generally specify requirements for carrying out inspections.