An open joint is a drain connection where the seal between two adjoining pipe sections has degraded or failed entirely, leaving a visible gap inside the pipe. The most frequent cause in Greater London is the deterioration of cement mortar joints in nineteenth century clay drains, although rubber gaskets in later installations can also perish or distort. Open joints allow tree roots to enter, water to escape into the surrounding ground and silt or soil to wash into the pipe. The combination of these effects often leads to recurring blockages and progressive ground washout around the line. Engineers usually identify open joints during a CCTV drain survey, classifying them against the WRc Manual of Sewer Condition Classification. Repair typically involves a short patch liner, full length cured-in-place lining under BS EN ISO 11296, or localised excavation.
Open joint (drain)
Drain joint with a gap between adjoining pipes, allowing root ingress and water loss.
