A recurring blockage is one that returns within weeks or months of being cleared, almost always indicating an underlying structural or functional defect rather than a one-off cause. Typical culprits include displaced joints, cracked pipework, root intrusion, partial collapse, drain bellies and inadequate gradient. In North London Victorian terraces, original clay drains laid in the late nineteenth century are particularly susceptible to these issues. Building Regulations Part H1 sets out minimum gradients and access requirements for new work, but historic systems often fall short of current standards. Engineers usually carry out a CCTV drain survey in accordance with BS EN 13508-2 to identify the root cause, producing a written report graded against the WRc Manual of Sewer Condition Classification. Targeted repair, relining or local excavation typically addresses the underlying issue.
Recurring blockage
Drain blockage that returns repeatedly after clearance, indicating an underlying defect.
