Infiltration & Inflow Control

Infiltration & inflow (I&I) refers to rainwater and groundwater that enters the wastewater system. I&I reduces the useful life and capacity of the collection system and wastewater treatment facility. Too much I&I can lead to sewer backups or overflows, particularly when it rains.

“Infiltration” is water that enters the wastewater system through indirect connections, such as leaks in defective sewer pipes or manholes.

“Inflow” is water that enters the wastewater system through direct connections, such as:

  • Roof leaders
  • Sump pumps
  • Yard drains
  • Catch basins

The largest sources of inflow come from individual homes and businesses, where roof leaders and sump pumps are illegally connected to the wastewater system.

If your property requires redirection of an existing roof leader or sump pump to the municipal storm drain system, please visit the Department of Public Works webpage under “Documents, Forms & Resources” for information on stormwater connection discharge regulations and permit applications.

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