Drain – this includes all pipes, ﬁttings etc. laid to remove soil, waste or surface water from one building. Private sewer – this is a drainage system that serves two or more properties and they are jointly responsible for its maintenance and repair. Public sewer – any length of drain that is not covered by the above and is the property of the Local Authority who is responsible for all maintenance work. Surface water – the run-off of natural water from surfaces including paved areas, roofs and unpaved areas. Invert level – the vertical distance from the top of the manhole to the bottom of the main drain channel.