How is the ownership of sewers and sewers determined? The property that starts the flow stroke is called the “race head.” This pipe is private. Once the pipe crosses the border into a third country, it becomes a “side flow”. As soon as the second piece of land flows into the side drainage, the pipe becomes a “public sewer”. 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 maintained by Thames Water. . . .