Locating and classifying illicit connections with Distributed Temperature Sensing

Distributed Temperature Sensing (DTS) is a powerful tool to detect and locate illicit connections in storm sewers. The technique uses a fibre-optic cable inserted in a sewer pipe that is connected to a laser/computer instrument which can measure temperature simultaneously at many locations along the cable. This way, a detailed representation of insewer temperatures in both time and space is obtained. Variations in temperature are indications for discharge from illicit connections. Over the last years, DTS monitoring has been applied in storm water sewers in a number of municipalities in the Netherlands for detection of illicit connections. The DTS technique, however, is also capable of classifying the type of illicit connection. This helps the sewer system manager to properly define necessary further actions in resolving the illicit connections. This paper presents the capability of DTS to detect and classify illicit connections and suggests a classification system based on the nature of the illicit connection.