Inflow and infiltration (I&I)
Inflow and infiltration (I&I) refer to excess water entering a sewer system. Inflow occurs when stormwater rapidly enters through direct connections like downspouts, sump pumps, or manhole covers. Infiltration happens when groundwater seeps in through cracks, leaks, or deteriorated joints in pipes. Excessive I&I can overwhelm treatment plants, increase costs, and lead to sewer overflows.