Excess water that flows into sewer pipes from groundwater and stormwater is called infiltration and inflow.
Cause & Effect
Groundwater (infiltration) seeps into sewer pipes through holes, cracks, joint failures, and faulty connections. Stormwater (inflow) rapidly flows into sewers via roof drain downspouts, household sump pumps and drain tile, storm drain cross-connections, and through holes in manhole covers. Most infiltration and inflow is caused by aging infrastructure that needs maintenance or replacement.