A pre-construction drain survey is carried out before construction work begins to establish a baseline of drainage condition that can be compared with later inspections. The survey identifies existing defects, records pipe routes and chamber locations, and provides documented evidence in case of any disputed claims that the works have damaged drainage. In Greater London the survey is widely used on basement conversions, rear extensions, side returns and new build projects where significant excavation occurs close to existing drains. Engineers carry out the inspection to BS EN 13508-2, grading defects against the WRc Manual of Sewer Condition Classification. The output forms part of the contractor's risk management documentation and supports party wall procedures and Building Regulations Part H submissions. Repeat surveys after completion confirm that drainage performance has been maintained.
Pre-construction drain survey
Drain inspection prior to construction work to baseline drainage condition.
