skip to main content

Infiltration and Inflow Control

King County, Washington

For more information about the Regional Infiltration and Inflow Control Program, please contact Steve Tolzman.

Wastewater Treatment Division
King Street Center
Suite 0505
201 South Jackson Street
Seattle, WA 98104

Get Directions to our office location in Seattle, Washington

Why is I/I a problem?

Extra water in the sewer system is a problem because:

  • It takes up capacity in the sewer pipes and ends up at the regional wastewater treatment plants where it must be treated like sewage, resulting in higher treatment costs.
  • Requires new and larger wastewater facilities to convey and treat larger volumes of flow, resulting in higher capital expenditures.
  • I/I flows contribute to sewer system overflows into local homes and the region's waterways, negatively impacting public health and the environment.

 peak flows diagram
We estimate that inflow and infiltration makes up 75 percent of peak flows during winter, and much of this comes from private property.

Protecting the environment and decreasing wastewater treatment costs are the benefit of a regional I/I control program.

» Finding Infiltration and Inflow (I/I)

Related Information