Wastewater Treatment sub Service Group Page Icon 1

Inflow and infiltration study today was known as a Sanitary Sewer Evaluation Study.

Wastewater I&I sub Service Group Page Icon 2

Excessive inflow and infiltration typically results in basement backups.

Inflow and Infiltration

Every sanitary collection system experiences some form of inflow and infiltration (I/I) impacting the performance of the sanitary sewers. However, excessive I/I typically results in basement backups of raw sewage or overflows of raw sewage into the environment.

An inflow and infiltration (I/I) study is typically the best way to determine sources of clean water entering the sanitary collection sewers. Historically what we call an I/I study today was known as a Sanitary Sewer Evaluation Study (SSES). There are similarities between them, and the terms are often used interchangeably.  


A typical I/I study may include some or all of the following:

  • CCTV using NASSCO assessment standards
  • Flow monitoring
  • Smoke testing
  • Dye testing the storm collection system
  • Dye testing private property downspouts, yard drains, other clean water sources
  • Computer modeling of the collection system

The data collected from the various study elements are used to develop repair and replacement recommendations for both the sanitary collection system and storm collection system and it may require private property improvements with the requirement of who pays for the improvements to be decided.

Inflow and Infiltration Services

  • Sanitary Collection Modeling – SWMM, PCSWMM, SewerCAD
  • Sanitary Sewer Evaluation Study (SSES)
  • Infiltration and Inflow (I/I) Investigations, including Smoke Testing, Dye Testing, and CCTV
  • Pipe Condition Assessments
  • Collection System Rehabilitation Study and Design
  • Collection System Capacity Analysis
  • Collection System Design
  • Pump Stations and Force Mains
  • Combined Sewer Overflow (CSO) Elimination Study and Design
  • Sanitary Sewer Overflow (SSO) Elimination Study and Design