Extra groundwater and rainwater in the sewer system – known as “inflow and infiltration” — takes up sewer capacity that is needed to handle wastewater. This can lead to sewer overflows and uses sewer space that is needed to service our rapidly growing region.
Both local government and private property owners have a role to play in reducing inflow and infiltration. Metro Vancouver is using various approaches to help manage the impacts of I&I, including wet weather sewer pricing.
What is inflow and infiltration?
Inflow and infiltration (I&I) happens when extra groundwater and rainwater flows into sanitary sewers. Sanitary sewers are designed to carry wastewater from sinks and toilets. There is often some extra rainwater and groundwater in sanitary sewers, but aren’t made to handle large amounts of it.
This extra water enters sewers through:
- Holes or cracks in pipes caused by damage, age or tree roots
- Leaky pipe joints and maintenance covers
- Roof and foundation drains that are improperly connected to a property’s sanitary sewer line
Some of this extra water gets in through municipal and regional sewers, but a lot of it also comes from pipes on private properties.
|Inflow and Infiltration Fact Sheet
|https://metrovancouver.org/services/liquid-waste/Documents/inflow-and-infiltration-fact-sheet.pdf, Inflow and Infiltration Fact Sheet
|Inflow and Infiltration Fact Sheet
Extra water can overload sewers
A little extra water from individual properties may not seem like a big deal, but it can quickly add up to become more than the wastewater system was designed to handle. This can lead to sewer overflows into homes, businesses and the environment. This extra water is a particular challenge in the wet fall and winter months, especially as we start to see more atmospheric rivers due to climate change.
Learn more about sewer overflows
What property owners can do
Property owners play a key role in reducing I&I: about half of our region’s sewer system is made up of pipes on private properties. Property owners have a responsibility to maintain the sewer lines on their property and make sure that nothing is improperly connected to those lines.
To stop large amounts of extra water from getting into your pipes:
- Have your pipes inspected with a camera by a plumber or drainage specialist at least once a decade
- Fix or replace old or damaged pipes, especially if they are “combined” sewer lines that carry both sanitary wastewater and stormwater
- Ensure downspouts and foundation drains are not connected to your sanitary sewer pipe
- Avoid planting water-loving trees or shrubs on top of your sewer line or drain pipes, as their roots can pry open joints between pipes
What Metro Vancouver is doing:
Metro Vancouver is working with its member municipalities to reduce I&I by:
- Incorporating reduction targets and strategies into regional wastewater planning, including wet weather pricing to better allocate costs to those contributing to the problem (see information below)
- Helping identify neighbourhoods with high levels of I&I and working towards solutions for those areas
- Upgrading infrastructure and planning for future growth, and conducting regular maintenance, to reduce the risk of future sewer overflows
- Exploring ways to encourage fixing problems on private properties
Wet weather sewer pricing
Metro Vancouver introduced wet weather sewer pricing in 2024. Member municipalities pay fees that reflect the sewer capacity they use during wet weather. This user-pay approach means that communities with higher I&I contribute more toward the regional sewer system.
The goal of wet weather sewer pricing is to have every community pay for the amount of water they send through the sewer system. It also aims to make sure that we are investing in expanding sewer and treatment capacity only when it is needed to accommodate population growth, and not to address gaps in infrastructure maintenance. Wet weather pricing will be phased in over ten years. Pricing is established in the GVS&DD Cost Apportionment Bylaw, 362, 2023.