The European coding standard for CCTV inspection of drains and sewers.

EN 13508-2 is strictly a descriptive standard, not an assessment standard. It provides the vocabulary to describe what is observed inside a drain or sewer — a crack’s orientation, width, and position — but it does not assign a severity grade or condition score. This separation of description from assessment is deliberate: it allows different countries to apply their own grading methodologies to the same underlying data. Germany uses DWA-M 149-2 to convert EN 13508-2 observations into rehabilitation priorities, the Netherlands uses the RIONED classification, and the United Kingdom uses the Sewer Rehabilitation Manual (SRM). All three produce different condition indices from identical field data, because each country has different rehabilitation thresholds and investment priorities.

Every observation follows the same four-part syntax: a Main Code identifying what was seen, one or two Characterisations refining the observation, a Quantification measuring its extent or severity, and a Location expressed as chainage (distance from the start node in metres) plus a clock reference (1–12) for circumferential position. This layered approach ensures that two operators inspecting the same pipe produce functionally identical records, even if they work for different contractors in different countries. The consistent syntax also makes the data machine-readable — grading software parses the codes automatically without manual interpretation.

The standard applies to gravity drains, sewers, manholes, and inspection chambers. It covers CCTV (closed-circuit television) inspections as well as man-entry visual surveys of larger-diameter pipes. A typical inspection begins at a manhole (the start node), with the camera travelling toward the next manhole (the finish node), logging each defect or feature encountered along the way. The operator adds observations sequentially in ascending chainage order — ensuring the inspection record reads as a chronological, spatially ordered log of the pipe’s internal condition.

The first layer is the Main Code — the three-letter identifier from the catalog. The second layer adds one or two Characterisations, each a single letter that refines the observation. For a crack (BAB), Characterisation 1 describes the orientation: A for longitudinal, B for circumferential, C for complex or multiple, D for spiral. For roots (BBA), the same letter position describes root type: A for tap root, B for fine roots, C for mass or clump. For infiltration (BBD), the letters describe flow intensity: A for seeping, B for dripping, C for running, D for gushing. The meaning of each characterisation letter is context-dependent — it changes based on the main code it accompanies. This is the aspect of the standard that requires the most operator training.

The third layer is Quantification — a numeric measurement that makes the observation objective and comparable. For cracks (BAB), Quantification 1 records the width in millimetres, typically categorised as hairline (less than 1 mm), moderate (1–5 mm), or wide (greater than 5 mm). For deformation (BAA), it records the percentage reduction of the pipe’s cross-section — a critical structural metric. For connections (BCA), Quantification 1 gives the diameter of the lateral pipe in millimetres, while Quantification 2 records how far the connection protrudes into the main pipe bore. For roots (BBA), quantification measures the percentage of cross-section lost to root growth. Not every main code requires quantification; some observations like vermin (BBF) or the inspection start marker (BDA) are purely categorical.

The fourth layer is Location, expressed in two dimensions. Longitudinal position is recorded as chainage — the distance in metres from the start node (e.g., 14.3 m). Circumferential position uses a clock reference from 1 to 12, where 12 is the crown (top) of the pipe and 6 is the invert (bottom). A defect spanning from 10 o’clock to 2 o’clock is recorded with Clock Start = 10 and Clock Finish = 2 — indicating it wraps over the crown. This dual-axis location system pinpoints every observation in three-dimensional space within the pipe, enabling precise mapping of defect progression over repeated inspections.

Every inspection run is defined by a start node and finish node — typically two manholes at either end of the pipe section. The operator records the inspection direction (upstream, travelling against flow; or downstream, travelling with flow), which determines how chainage distances are measured. The pipe shape is recorded using EN 13508-2’s single-letter codes: A for circular, B for egg-shaped, C for rectangular, D for square, E for oval or elliptical, F for horseshoe, and Z for any other profile. Pipe dimensions are entered in millimetres — for circular pipes only the height (internal diameter) is required, while non-circular shapes require both height and width measurements to define the full cross-sectional geometry.

The pipe material is coded with a single letter: A for concrete, B for brick or masonry, C for clay or stoneware, D for fibre cement, E for PVC, F for PE (polyethylene), and further codes through to Z for other materials not in the standard list. The operator also records whether a lining is present — this changes how certain defect codes should be interpreted, since a crack in a lined pipe may indicate lining failure rather than host pipe damage. Weather conditions at the time of inspection and any pre-cleaning method used (jetting, flushing, or winching) complete the header record. These fields are not just administrative: they directly influence how downstream grading software interprets the observation codes. A 5% deformation in a rigid concrete pipe is structurally far more significant than the same measurement in a flexible PE pipe.