Inflow & Infiltration

Help prevent Inflow and Infiltration from your property Infiltration and Inflow (I&I) are terms used to describe groundwater and stormwater entering the sanitary sewer system. Infiltration of groundwater can occur through leaky pipe joints or damaged pipe sections. Sources of Inflow include foundation drains (weeping tile), sump pumps and roof drains that are improperly connected to the sanitary sewer system.

Recent studies indicate that approximately 1/3 of all sanitary sewer flows are a result of Inflow and Infiltration (I&I) from private property. During a rain storm, some sewers are flowing completely full.

As a property owner you are responsible for maintaining the sewer lateral (pipe) that connects your house to the sanitary sewer system. You can help reduce I&I in a number of ways.

  • Avoid planting trees and shrubs over sewer laterals as roots may grow into the pipe and restrict the flow, damage pipes and allow I&I to take place.
  • Replace any known broken or leaking sewer laterals and plumbing fixtures within the building.
  • Check your gutters and drains to ensure they are not connected to the sanitary sewer.
  • Ensure sump pumps and foundation drains (weeping tile) are connected to the storm sewer or discharged to the surface at a swale or ditch.

Why rainwater should be kept out of the sanitary sewer system

In the province of Ontario regulations require the sanitary sewers be separate from the stormwater drainage system. By-laws are also in place to restrict the improper connection to the sanitary sewer. These laws help ensure the safety of residents and the health of the environment.

Sanitary Sewer System

Sanitary sewer pipes receive wastewater from fixtures within buildings, such as toilets, showers, sinks, dishwashers, washing machines and floor drains. These pipes move wastewater to the treatment plant at Memorial Drive. When treatment is complete it is then discharged to Lake Nipissing.

Stormwater Drainage System

The stormwater drainage system is designed to move rain water and groundwater. This system includes underground pipes, ditches, and rear lot drainage swales. Flow enters the system from a variety of points such as, roof drains, foundation drains (weeping tile), sump pumps, yard drains, and catch basins. All stormwater flows discharge into nearby lakes, rivers, creeks, and streams.

Effects of rainwater and groundwater in the sanitary sewer system

During a storm, rain and groundwater can end up in the sanitary sewer, affecting capacity and even causing problematic overflows and backups. When flows are too high they may bypass complete treatment and discharge directly into Lake Nipissing. Sewage Backup The amount of Inflow &Infiltration varies in the system. In some areas of the city the amount is substantially higher than others.

To ensure the safety of residents and of the environment, our stormwater drainage flows must be kept separate from the sanitary system.

How will we find sources of Inflow and Infiltration

There are a number of ways to locate problem areas and include the following:

  1. Flow Monitoring - Key sewer system locations are identified to place flow monitoring sensors within the pipes. This data is then analyzed, along with the rainfall data, to see if there are excessive flows within the targeted areas. Flow sensor within the pipe
  2. Camera Inspection - Closed circuit television inspections (CCTV) use a video camera to record the condition of a sewer pipe. The camera “tractor” is remote controlled from the surface; video footage is reviewed to identify any defects such as cracks, root intrusions or leaky joints. Certain techniques can be used to repair these defects from within the pipe. Before and after photos of ground water gushing in a leaking joint, then the joint repair and pressured tested.
  3. Dye Testing - Dye testing may be conducted to confirm connections to the sewer. The test involves adding a special non-toxic dye to the suspect connection and to monitor the downstream sewer manhole for the presence of the dye. Green Dye (left Side)
  4. Fog Testing - Fog testing involves injecting fog into a sewer manhole and noting where the fog comes to the surface. The goal of the test is to identify direct stormwater connections to the sewer system, also known as cross-connections. The fog is non-toxic, stainless, odorless and vegetable based. Proper Connection Improper Down Spout Connection Improper Foundation Connection 

If you have any questions about Inflow and Infiltration please contact the City engineering department, 705-474-0626 ext. 2320



Download the Inflow and Infiltration Program Guide