Inflow & Infiltration Elimination Program

Inflow and Infiltration (I&I) occurs when groundwater and/or rainwater enters the sanitary sewer system, travels through pump Smoke Testing Illustrationstations and ends up at the wastewater treatment plant, necessitating its treatment just as if it were waste water.

This additional volume of water imposes an unnecessary burden on the city treatment facility. Elimination or reduction of this excess water in the collection system will help remove one of the causes for sewage overflows in the City and reduce the cost of sewage treatment. For instance, when excessive rainwater enters the system it may result in sewage overflows from manholes into the streets or even has the potential to backup into homes. The fix is to find and eliminate areas where I&I creates such problems, and one of those methods is smoke testing.

Smoke Testing

The city will begin smoke testing the entire system of sewer collection basins outside of the city in St. Johns County starting in November 2020.  View a sample project information flyer (PDF) and a map of the current testing area .

As simple as it seems, one of the most effective ways to find leaks or unintended pipe connections is to push smoke through specific sections of the sewer system and identify where it exits. In this case, where your see smoke is not a fire, it is a potential source of I&I.

Smoke Materials Used

Materials used to generate the smoke are non-toxic, harmless, virtually odorless, and do not create a fire hazard, nonetheless every effort is made to alert the public when there is smoke testing in their area. Public door hanger notification distributed to residents and commercial areas approximately one to three days in advance. The door hanger describes testing and what should be done in advance to minimize smoke from entering buildings. Residents do not need to be home during the testing, and contact information will be provided on the door hanger in the event smoke does enter a building.

Preparing for Smoke Testing

Smoke should not enter into buildings unless leaks or plumbing defects exist, including faulty wax ring seals at the base of toilets, or infrequently used drains. In the case of drains, the public is advised to pour approximately 24 ounces of water into each drain thus creating a barrier for the smoke. Drains can be prepared as soon as notification has been issued for testing in the area and need only be prepped once before testing in the area begins.

If Smoke Enters a Room

In the event smoke should enter a building, there is a chance smoke alarms may be activated. In such cases, rooms should be ventilated through an open window or door. Acute exposure can cause irritation of the respiratory system so occupants are urged to ventilate well to dissipate the smoke, leave the area if any irritation is experienced and use the contact information included on the door hanger to notify the authorities.


Email the Public Works Department if you have questions or concerns or call at 904-825-1040.