All sewers and side sewers built before July 1, 2011 and connected to our network are all part of the public sewer system owned by Thames Water and managed by Thames Water. There are different applications for different sizes of sewers. Class 1 1 160 mm in diameter or smaller (domestic/commercial) Class 2 160 – 375 mm in diameter Class 3 more than 375 mm Diameter For all classes, with the exception of Class 1 on the national territory, we must carry out, before the start of the work, a surveillance examination for the closed circuit (CCTV) to determine if repair work is necessary. Further examination is needed when your building is completed to verify that the sewers have not been damaged. Class 1 and Class 2 fees cover all stages of processing and agreement; on the other hand, Class 3 would require additional budget for attorneys` fees and investigations carried out by Thames Water, which can amount to thousands of additional pounds. . . .