Find out why it's important to keep rainwater and groundwater out of the sanitary sewer system.

Rainwater and groundwater in the sanitary sewer system (also referred to as Inflow and Infiltration or I&I) reduces the sewer's ability to carry wastewater. This may cause sewer backups into homes or businesses, or overflows to roads, creeks or sensitive habitat areas. It also means groundwater and rainwater will be sent to the wastewater treatment plant for cleaning, which is unnecessary for this kind of water.

Metro Vancouver requires all local municipalities to limit the amount of rainwater and groundwater in the sanitary sewer system under the Integrated Liquid Waste and Resource Management Plan.

Keep Rainwater and Groundwater out of Your Sanitary Sewers

Studies have suggested that up to 70% of the rainwater and groundwater in a sanitary sewer system comes from private property.

Help us reduce rainwater and groundwater in the sanitary sewer system by doing the following:

  • Ensure your roof downspouts carry water to your lawn, and not underground to your sanitary service connection. This is a requirement in the City’s Stormwater Drainage Regulation and Charges Bylaw No. 16610 and Sanitary Sewer Regulation and Charges Bylaw No. 16611.
  • Hire a plumber to video your service connection to see if there are leaks, blockages or signs of rainwater or groundwater entering your service connection.
  • Fix or replace broken or missing lids or caps on your foundation (perimeter) drain cleanouts.
  • Report broken or missing sanitary lids, caps or manhole covers on City property.
  • Don’t plant trees, shrubs or other large plants over your service connection as the roots can damage the pipe.
  • If you have a swimming pool, do not empty pool water into the sanitary sewer when it is raining.

Monitoring Rainwater

The City measures the amount of rain that falls, as well as the amount of water in the sanitary sewer system. We use this information to estimate the amount of rainwater and groundwater in the sanitary sewer system at several locations in the City.

The monitoring results, along with our maintenance program results, help us to identify sanitary sewers with high levels of rainwater and groundwater. The City then decides what actions to take to reduce the amount of rainwater and groundwater in the system.

See our drainage section for more information.