Sewer involves the collection, treatment and disposal of wastewater. It includes sanitary sewer collection, pump stations, force mains, treatment plants, wastewater resuse, & all related work. It does not include stormwater or drainage.
In some cases stormwater (storm sewer) and sanitary sewers use the same pipes. However, this is no longer allowed in the US and the two are required to be separated into different pipes.
Simple sewer system