A drain collapse occurs when the structural integrity of a pipe fails, with the bore deforming inward, fracturing or losing alignment so that flow is restricted or stopped entirely. Common causes include age-related deterioration, ground movement, traffic loading on shallow runs, corrosion of cast iron sections, and longstanding root intrusion. In North London Victorian terraces, original clay drains laid in the 1890s are now well past their typical design life and collapses are encountered routinely during CCTV surveys. Symptoms include recurring blockages, sinking ground over the line of the drain and unexplained overflow externally. Engineers usually identify the location and extent through a CCTV survey graded against WRc condition classifications. Repair options include patch lining, full length relining under BS EN ISO 11296 or open-cut replacement where damage is extensive.
Drain collapse
Structural failure of a drain pipe where the bore deforms or fractures, blocking flow.
