Salt-glazed clay pipe is an earlier variant of vitrified clay made between roughly 1850 and the 1960s, produced by introducing salt into the kiln to create a smooth, glassy glaze. It remains widespread across Victorian and Edwardian housing in inner London boroughs, often laid in 100mm or 150mm diameters with cement-mortar socket joints. The salt glaze provides good resistance to sewage and surface water but the rigid jointing makes the system vulnerable to ground movement, leading to displaced joints, infiltration and root entry. Engineers identify salt-glazed clay on CCTV by its dark glossy interior and brick-built junctions. Replacement is rarely necessary if structural condition is sound, with patch repair or full-length CIPP lining used to restore performance.
Salt-glazed clay pipe
Older vitrified clay pipe with a glossy salt-glaze finish, found in Victorian London.
