Inflow and Infiltration

Inflow and infiltration happens when water from the environment enters the sewage system for treatment.

York Region has two sewer systems:

Sewage system (sanitary sewer)
Storm sewer

The sewage system is designed to carry sewage to treatment plants for processing before returning it to the environment. The storm sewer prevents streets from flooding by draining and carrying excess stormwater (water from rainfall and snowmelt) to lakes and streams.

Image of broken ground with water seeping through to sewer

What is Inflow and Infiltration and why is it a problem?

What is Inflow and Infiltration?

Inflow and Infiltration happens when water, groundwater and stormwater enters the sewage system through sump pumps, downspouts, and/or holes and cracks in the pipes.

House indicating sources of inflow and infilltration

View videos showing common sources of inflow and infiltration in:

Why is Inflow and Infiltration a problem?

Inflow and infiltration are problems because they:

Reduce the capacity of the sewage system leaving less for existing residents and future growth
Make sewage treatment less efficient as the sewage is diluted by water
Increase the cost of water to residents because sewage treatment plants are required to treat a higher volume of flow
May cause sewage backups in basements
May overwhelm wastewater treatment plants

Videos are courtesy of Capital Regional District (CRD).

What you can do to prevent inflow and infiltration?

There are a few simple things you can do to ensure your property doesn’t contribute to inflow and infiltration.

Ensure your home’s downspout is disconnected from the sanitary sewer system and flowing properly towards the storm sewer
Ensure sewer grates on your street are free from debris such as leaves and garbage to ensure storm water drains properly
Use a rain barrel
Participate in Regional and City/Town Inflow and Infiltration reduction projects happening in your neighbourhood

The infographic below explains the difference between an incorrect and properly connected downspout.

infographic showing the correct and not correct way to have a downspout on your home.

Current inspection and repair work projects

York Region in partnership with local cities and towns undertaking projects to reduce high amounts of rainwater, melted snow and groundwater entering the sewer system through inflow and infiltration. For questions, please contact Access York at 1-877-464-9675 or email [email protected]

What to expect when inflow and infiltration inspection or repair work is happening in your neighbourhood?

Once a source of inflow and infiltration has been found, York Region and/or local cities and towns begin repair projects which may include:

Repairing defects such as cracks or holes in pipes
Disconnecting known inflow sources, such as downspouts from the sewage system
Reviewing and updating construction design standards
Developing new standards and guidelines for inspecting and testing the sewage system

Trenchless technology is used to repair or replace pipes with minimal digging or disruption to property. Examples of trenchless technology include:

Pipe bursting - Replacing an older pipe by sending a new pipe through the old one and “bursting” (destroying) it from the inside
Relining - Creating an epoxy lining inside of an existing pipe
Cured-in-place pipe - Creating a pipe within an existing pipe

What York Region is doing about inflow and infiltration?

Finding and reducing inflow and infiltration is a high priority. It reduces the cost of treating stormwater water as sewage, helps to maintain and extend the life of costly infrastructure and helps to ensure there is enough capacity for wastewater to move through the system.

Finding Sources of Inflow and Infiltration

York Region monitors rainfall and the sewage system to find areas with higher-than-expected water flow.

York Region and/or local cities and towns further investigate on-site by using mobile video cameras to perform a closed-circuit television inspection.

We may further investigate sources by forcing vegetable-based, non-toxic, odourless smoke into sewer maintenance holes or adding a non-toxic dye to an upstream freshwater source believed to be contributing to inflow and infiltration.

Reducing Inflow and Infiltration

Once a source of inflow and infiltration has been found, York Region or local towns and cities inspect and repair issues in manholes and sewer lines, reducing inflow and infiltration in the community’s sewage system.

York Region also proactively applies inflow and infiltration reduction practices into the design and construction of new sewer systems and rehabilitation projects, ensuring new infrastructure is monitored right from the beginning. View full details on Inflow and Infiltration Reduction Standard for Sewers Servicing New Development.

What local cities and towns are doing about inflow and infiltration

Aurora