No substances other than rain and melted snow can be poured or allowed to flow into an outdoor catch basin (square grates on the street). This includes:

  • oils and grease
  • soaps and other cleaning products
  • water leaking from a waste/oil bin
  • any water used for cleaning (e.g. mop water)
  • solid materials (e.g. cigarette butts, tissues, wrappers, etc.)

Anything other than rain or melted snow that enters a catch basin is considered a spill and can cause damage to the sewer system, pollute the environment and harm aquatic habitat. If you suspect a spill, please contact 311 immediately.

Tips for Washing Wisely

Washing your car

Dirt on cars can contain toxic chemicals, heavy metals, oil and grease. To keep dirty water out of the sewer system, consider these options for washing your car:

  • Use a commercial car wash facility (automatic or coin). These facilities are required to follow a set of practices determined by the City, including treating wastewater and discharging it into the sanitary sewer system where it will receive further treatment.
  • Find a location where the wastewater won’t flow into the storm sewer. For example, washing cars on a permeable surface such as gravel allows the wastewater to be absorbed before it reaches the storm sewer.
  • Dispose of the wastewater into the sanitary sewer. By using a pail, washcloth and only a small amount of water, and then wiping the car dry, the wastewater can be contained in the bucket and disposed of into the sanitary sewer through a laundry sink or toilet. From there it will go to a City wastewater treatment plant.

General tips for outdoors

  • Keep chemicals out of sewers:
    • never pour anything down manholes or catch basins
    • clean up vehicle spills or leaks to prevent toxins from entering the sewer
    • see how to dispose of Household Hazardous Waste
  • Properly dispose of water from pools, hot tubs and spas.
  • Sweep sidewalks and driveways clean instead of using a running hose.

The Sewers By-law sets strict limits on what can go down a storm sewer to help protect public safety and the environment. See Table 2 in the Sewers By-law for a full list of limits by parameter.

Outdoor wastewater disposal

  • Wastewater from outdoor washing must not reach any catch basins as soaps, cleaning products and contaminants dislodged or dissolved from the surface being washed will violate storm sewer By-law limits.
  • This includes water used for graffiti removal, building restoration, as well as vehicle, sidewalk, alley or other outdoor washing.
  • Power washing with water alone will still dislodge or dissolve contaminants from the surface being cleaned.


  • Let the water evaporate.
  • Re-route it away from a catch basin and/or contain it.
  • Dispose of it in an indoor drain or haul it off-site.
    • Disposing in an indoor drain may require treatment to meet the sanitary sewers By-law limits.
    • Hauling off-site must be performed by a Ministry of the Environment, Conservation and Parks approved hauler.

Washing outdoor garbage areas

  • Outside garbage areas should not be cleaned using running water.
  • If wastewater reaches a catch basin, it will violate the limit for suspended solids and possibly food products.


  • Keep the outside area clean by disposing of garbage in a way that does not require washing and by continually sweeping the area.
  • Use containment berms around the perimeter of outdoor waste bins and garbage compactors to capture any leaks.
  • If washing is necessary, use the disposal method listed above to evaporate, re-route away from catch basins and/or contain the water.

Mobile wash business operations

  • Make sure to hire a company that follows the Sewers By-law as both the person hiring and the mobile wash business operation/company are responsible for wastewater discharging from the property.
  • Mobile wash businesses include companies that wash cars and buildings, landscapers washing windows, duct cleaning companies washing roof exhausts, etc.
  • Toronto Water is currently working on an Environmental Code of Practice for Mobile Wash Businesses to help operators comply with the By-law.