Which sewer system includes surface, drain, and storm run-off?

The combined sewer system is designed to handle both wastewater from residential and commercial sources as well as stormwater runoff. This means that it collects sewage and stormwater in the same pipe. During dry weather, the system transports this combined flow to a treatment facility. However, during heavy rainfall or snowmelt, the volume of water can exceed the system's capacity, potentially leading to combined sewer overflows, which can discharge untreated waste into nearby water bodies.

In contrast, a sanitary sewer system is exclusively for wastewater, which includes sewage from bathrooms, kitchens, and other household or industrial sources, and does not accommodate stormwater. A separate sewer system is designed solely for stormwater runoff, thus keeping it completely separate from any sewage. Finally, an industrial sewer system primarily manages wastewater arising from industrial processes, again focusing solely on waste without encompassing stormwater.

The distinction of the combined sewer system is significant as it addresses both types of flow, reflecting its dual functionality in urban infrastructure.