A drain tracer, or sonde, is a small battery-powered transmitter mounted at the end of a CCTV camera rod or pushed through a pipe on a separate rod. It emits a low-frequency electromagnetic signal that can be picked up at ground surface by a hand-held receiver, allowing engineers to mark the exact route and depth of the drain. The technique is essential when investigating unknown drainage layouts, identifying lost connections, locating soakaways and confirming the line of a defect for targeted repair. Sondes are used routinely on London survey work in conjunction with CCTV inspection under BS EN 13508-2. The combined output supports accurate drain mapping, no-dig repair planning under BS EN ISO 11296 and any required excavation to BS EN 1610. The work is carried out by qualified engineers.
Drain tracer (sonde)
Electronic sonde inserted into a drain that emits a signal detected at ground surface.
