ABSTRACT
Urban areas may be sewered by a combined system, a separate system, or a partially separate system. In a combined system, which is the most common in Britain, one network of sewers collects foul sewage and stormwater. In a separate system two sewer networks are used, one for foul sewageand the other for stormwater. A partially separate system is a compromise allowing some of the precipitation, e.g. from the backs of houses, to flow into the foul sewer; the second sewer carries the rest of the storm water.
