The management of wastewater networks is essential to ensure optimal hydraulic modeling. However, data on wastewater systems, usually represented in Geographic Information Systems (GIS), are often incomplete. Other sources of information are thus required to complete them. Among these, pipe inspection videos, so far mainly used for maintenance and detection of anomalies such as degradation, can be used for this purpose. This article goes in this direction and proposes to take advantage of these inspection videos to extract the structure of wastewater networks, represented here in the form of graphs. For this, we propose automatic detection mechanisms of the different annotations associated with the inspection videos. These annotations contain enough information to compose a graph of the wastewater networks. Regular expressions and text recognition tools, based on optical character recognition (OCR), are used to extract manholes identifiers, water flow direction in pipelines, as well as other useful information to determine the geographical positions of wastewater network objects. Experimental results on real data show the good performance of our method.