Inflow is water other than sanitary wastewater that enters a sewer system from sources such as roof leaders, cellar / foundation drains, yard drains, area drains, drains from springs and swampy areas, maintenance hole covers, cross connections between storm sewers and sanitary sewers, and catch basins.
Infiltration is water other than sanitary wastewater that enters a sewer system from the ground through defective pipes, pipe joints, connections or maintenance holes.
Inflow and Infiltration Problems
There are a number of problems caused by inflow and infiltration, including:
Basement flooding: Too much water in the sanitary system can cause water to back up into basements
Overflows into the environment: To prevent basement flooding during extreme wet weather events, a combination of storm water and wastewater is released into the environment to alleviate capacity. Learn about combined sewer overflows.
Reduced system capacity: Restricts available capacity for current residents and prospective future growth
Increased costs to residents: Excess flows of clean environmental water is needlessly collected, transported and treated at the wastewater treatment plants
Dilution in sanitary sewers: Reduces efficiency of treatment plants
Video: Inflow and Infiltration Introduction
Video: Impact of Rainwater on our Sanitary Sewer System
How You Can Help
We all have an important role to play in reducing the impacts of inflow and infiltration on our sanitary system. Look out for these common sources at home:
Downspouts connected to the sanitary system: Try redirecting yours into a rain barrel for water to use later or a rain garden as an alternative
Private side lateral damage: Be aware of aging pipes and of nearby trees that can cause root damage
Weeping tiles and / or sump pumps connected to the sanitary system: Some municipalities offer weeping tile and sump pump disconnection subsidy programs, so check with your local municipality to see if you qualify