Storm Water

Rain and storm water enter the wastewater treatment system in two ways: inflow and infiltration.

  • Inflow is when rain gutter downspouts, weeping tiles and sump pumps are connected directly to sewers. During a heavy rainfall, all this water flowing directly into the sewer can be more than the sewer can handle, leading to basement flooding and discharge into the environment.
  • Infiltration is when groundwater enters the sewer system through broken or cracked sewer pipes and manholes.

Storm water infographic

What you should know about storm water

Cost to you

Storm water is not meant to be treated by our wastewater treatment facilities, but if it enters the sewer system it has to be treated because it is mixed with sewage.  Having unnecessary water being treated increases costs which, in turn, can lead to increased wastewater rates for you.

Human and environmental health

If too much water enters our wastewater treatment facilities it may cause an overflow of wastewater that has not been fully treated. Having untreated wastewater re-enter the environment can impact the health of humans and the environment. See our Wastewater Bypass and Overflow Reports.

Sewer backup on your property

Sewer backups happen when sewer systems receive more water than they can handle.  This results in property damage, loss of personal belongings and expensive clean-up.

Learn how to prevent basement flooding and what to do if you experience a sewer back up.

What you can do about storm water

You must disconnect your rain gutter downspouts, weeping tiles and sump pumps from emptying into the sewer system. This is part of our Sewer Use By-Law. Learn more about our preventative plumbing subsidy program.

  • Keep the area around downspouts free of blockages.
  • Put a rain barrel under your downspout for a free source of water for outdoor use.
  • Repair or replace broken sewer pipes between your home and the City’s main line.

Storm Water Study