Substruck Ltd. completes CCTV surveys in response to drainage or subsidence problems or as part of pre-purchase surveys. Our Phase 1 reports document a non-destructive investigation of the drainage system using one or a combination of direct observation, hydrostatic testing, CCTV surveying / inspection and drain tracing techniques.
A CCTV inspection / survey will identify
- structural defects (i.e. the physical condition such as broken or collapsed drains, holes, cracks, deformations, etc.),
- service defects (i.e. defects that determine the capability of the drain to meet its service requirements and indicate loss of capacity, potential for blockages and watertightness such as attached deposits, obstructions, roots, exfiltration, etc.),
- construction features (features relating to the construction of the drain/sewer such as location and condition of junctions and connections, defective seals, etc.) and
- miscellaneous features such as evidence of vermin, hazardous atmospheres, loss of vision, material/pipe length/size changes, etc.
The CCTV survey report is derived from CEN EN 135082:2003 Condition of Drain and Sewers Outside Buildings: Part 2 Visual Coding Inspection and WRc plc (2013) Manual of Sewer Classification 5th ed. For a CCTV survey and report, each defect will be assigned a Sewer Condition Grade as per the Sewer Risk Management (SRM5). For a hydrostatic drain test and CCTV inspection, the grade of a length of drain will be based on the worst defect as per WRc (2011).
CCTV inspection/surveying overcomes the limitations of hydrostatic testing, particularly during the identification and location of structural, service, construction and miscellaneous features and defects. Therefore, Substruck Ltd. advise that a hydrostatic test should not be completed without the aid of a CCTV inspection at the very least. However, as water can travel to areas where a camera unit cannot, we also advise that hydrostatic drain testing can overcome the limitations of CCTV surveying/inspection. Both techniques complement each other to give a more accurate representation of the drainage system.