What is I/I?

Infiltration/Inflow (I/I) is a term used to cover surface and groundwater that enters the system.


I/I reduces the capacity of sewers to carry wastewater, and can adversely affect the performance of the wastewater treatment plant. In addition, it is not uncommon for basement flooding or sanitary sewer overflows to occur because of I/I.

All sanitary sewer systems have I/I. The challenge is to reduce excessive I/I. The determination of what is excessive varies from community to community.

Identifying and removing I/I can be a time-consume and expensive task if not properly pursued. Jones & Henry can help a community address the I/I problems in a cost-effective manner.


Jones & Henry has assisted many communities in programs designed to minimize I/I. Our experience with I/I has resulted in several solutions to different I/I problems. Solutions are developed following a cost-effective analysis of the situation.

Some of the solutions that have been recommended by Jones & Henry and implemented to control I/I include:

  • Manhole Rehabilitation
  • Sewer Lining
  • In-line Storage
  • Sanitary Relief Sewers
  • Public Awareness Program
  • Internal Sewer Grouting
  • Sewer Replacement
  • Equalization at the WWTP
  • Foundation Drain Removal
  • Express Sewers


Jones & Henry provides full service to arrive at a comprehensive program to remove excessive I/I. We tailor our services to your needs. We offer:

Data Collection:

  • Continuous Flow Monitoring
  • Smoke Testing of Storm & Sanitary Sewers
  • Dye Testing of Storm Systems
  • Visual Inspection
  • Manhole Evaluations
  • Television

Preliminary Analysis:  Preliminary analyses completed by Jones & Henry include the following:

  • Statistical review of WWTP flows
  • Review ratio of potable water to wastewater flows
  • Analysis of past flooding problems

Project Report and Recommendations

The findings of the investigation, including financial capability analysis to select approach to the problem, are contained in a report. The report also includes recommendations as well as preliminary costs.


Jones & Henry has the resources and experience to help you develop a successful program. Realistically, a program that reduces I/I by 25 to 30 percent is considered successful. The results of such a program help to solve many problems and contribute to enhancing public health.


Jones & Henry
Engineers, Ltd.