What is the difference between "infiltration" and "inflow"?

The distinction between infiltration and inflow is crucial for understanding sewer system challenges. Infiltration specifically refers to groundwater seeping into the sewer system through cracks, joints, or other openings in the pipeline. This typically happens when the water table rises, allowing groundwater to invade the sewer lines. In contrast, inflow pertains to stormwater entering the sewer system from surface runoff, typically during rain events or through direct connections, such as catch basins or improperly connected roof downspouts.

By accurately defining infiltration as groundwater entry and inflow as stormwater entry, this answer highlights the different sources of extraneous water that can affect the efficiency and capacity of a wastewater collection system. Recognizing these differences is vital for developing appropriate management strategies to address sewer overflows and system capacity issues, especially during storm events.