Inflow and Infiltration Reduction Program

What is inflow and infiltration?

Inflow happens when stormwater enters the sewage system through sump pumps or downspouts still connected to the sewage system instead of the storm sewer.


Infiltration happens when water or groundwater from beneath the earth’s surface enters the sewage system through damage or defects such as holes and cracks in manholes and sewer pipes.


The city of Vaughan has two sewer systems: sewage system (sanitary sewer) and stormwater sewer. The sewage system is designed to carry sewage (mostly water) to treatment plants for processing before returning it to the environment. The stormwater sewer prevents streets from flooding by draining and carrying excess stormwater (water from rainfall and snowmelt) to lakes and streams.


Why is inflow and Infiltration a problem?

Inflow and infiltration is an issue because it reduces the capacity of the sewage system, leaving less water for existing residents and future population growth. It can also make sewage treatment less efficient as the sewage is diluted by water. This may increase the cost of water to residents because sewage treatment plants will then be required to treat a higher volume of flow. Inflow and infiltration may also cause sewage overflows or overwhelm treatment plants leading to health risks and property damage.


Vaughan’s reduction strategy 2016–20

The City of Vaughan is developing an Inflow/Infiltration Reduction Program to improve the service of the sanitary sewer system by reducing and mitigating adverse impacts resulting from potential inflow/infiltration sources. The reduction of inflow and infiltration will allow for effective service delivery and enhanced operational performance of the sanitary sewer system. Improving functionality of the sanitary sewer will contribute to creating a city with sustainable built form. Vaughan’s reduction strategy will support York Region's Inflow and Infiltration Reduction Strategy and Initiatives.


Flow monitoring

The City of Vaughan is implementing a flow monitoring program that uses flow meters to be installed in mini basins to identify high priority areas.


These flow meters will be monitored and the data that is collected will help distinguish significant inflow/infiltration occurrences.


Identification of inflow and infiltration sources

Sanitary Sewer Condition Assessment - Closed-Circuit Televisions (CCTV) inspections of mainline and lateral pipes to investigate possible sources of inflow and infiltration.


Private Property Programs - Smoke and dye testing to be performed to identify possible downspout and sump pump connections to the sanitary sewer system. This process involves forcing a vegetable-based, non-toxic, odourless smoke into sewer maintenance holes. If the smoke through sources not connected to the sewage system, may indicate the presence of inflow and/or infiltration.


Cross Connection Identification - Any possible storm sewer connection to the sanitary sewer to be identified through dye testing.


Next steps

Data collected from the video inspection, manhole inspection and smoke and dye testing will be used to create a list of target inflow and infiltration areas across the city. These areas will be prioritized for repair.