Inflow and infiltration (I/I) is a term use to describe when clean water, like stormwater and groundwater, enters wastewater collection systems.
Inflow is typically stormwater entering the collection system through sources like manhole covers and improperly connected sump pumps and roof downspouts. The amount of inflow peaks during and immediately after rainfall events, and can result in sanitary sewer overflows (SSOs) and basement backups.
Infiltration is typically groundwater that seeps into the collection system through sources like cracked sewer pipes or deteriorating joints. In areas with high groundwater, or when wet weather temporarily raises groundwater levels, infiltration can increase the base flow of the collection system.
Excessive inflow and infiltration takes away valuable capacity and diminishes the functionality of the sanitary sewer system.
Reduction of inflow and infiltration will benefit both the community and individual property owners by: