What does I&I stand for in sewer systems?

What does I&I stand for in sewer systems?

• A. Inflow and isolation
• B. Inflow and infiltration
• C. Internal and interconnection
• D. Impact and isolation

Answer: (B)

I&I stands for inflow and infiltration. Inflow is water from outside the sanitary sewer that enters the system through improper connections or direct drains, such as roof drains, yard drains, or sump pumps tied into the sewer. Infiltration is groundwater seeping into the sewer through cracks, broken joints, or faulty manholes, especially during wetter periods. Together, these two sources add extra water to the sewer, increasing flow to the treatment plant, risking overflows, and raising maintenance costs. Recognizing I&I helps crews identify and fix illegal connections, repair leaks, and separate stormwater from sanitary lines. The other terms don’t describe water entering the sewer system in these ways.