Watch the City’s series of videos to learn more about basement flooding prevention. Part 1: how your plumbing system works, sewer cleanouts, overland flooding, cleaning blocked or plugged eavestroughs and disconnecting downspouts. Part 2: weeping tiles, sump pumps, sewer back-ups and backwater valves and the financial subsidies the City provides when you install flood prevention devices.

Basements Can Flood for Many Reasons

While the City of Toronto is working to improve its complex system of underground pipes, sewers and catchbasins, these improvements alone cannot completely protect a home from basement flooding.

During heavy rain, the sewers can become overloaded. It is essential that homeowners take steps to help protect their home from basement flooding.

Watch Part 2 to learn about weeping tiles, sump pumps, sewer back-ups and backwater valves and the financial subsidies the City provides when you install flood prevention devices.

Know exactly what you are looking for? Click through the playlist below to view specific topic areas on basement flooding prevention.

Every home is at risk of basement flooding, even if it has not happened before. Water in your basement is most likely to occur during heavy rainfall, or when snow and ice is melting. You can take steps to help reduce or prevent it from happening.

There are a number of reasons why basements flood, including:

  • When stormwater or ground water seeps into the home (drainage failure) due to:
    • A crack or leak in your home’s foundation, basement walls, or basement windows or door
    • Poor lot grading or drainage
    • Failure of the weeping tile system (foundation drains)
    • Failure of a sump pump (in some homes) used to pump weeping tile water
    • Overflowing eavestroughs
    • Leaking or plugged downspouts
  • A sewer back-up caused by a blocked or overwhelmed sewer line.
    • Blockages are typically caused by items that are incorrectly flushed or poured down the drain, by tree roots and/or broken or cracked sewer lines.
    • Overwhelmed City sanitary sewers under the road can occur during heavy rainfall. If the sanitary sewers fill beyond capacity, the water can travel backwards in the sewer line and into the property.
    • Overland flow during heavy rainfall, stormwater (rain or melted snow) or groundwater can seep into the property due to: a crack or leak in the property’s foundation or basement walls, windows or doors; poor lot grading and/or drainage; failure of the weeping tile system (foundation drains) or a sump pump; overflowing eavestroughs; leaking or plugged downspouts; or unmaintained privately-owned catchbasins (this can be common on privately developed groups or properties). Overland flooding is unrelated to sewer service lines and City sewer infrastructure. Water found in basements from overland flooding is often more clear than brown and/or muddy.

If you don’t know how the sewer or water plumbing systems function at your property, it is important to contact a licensed plumber or other professional. This can help eliminate the distress and expense of a serious plumbing problem that can occur suddenly, for example, knowing where your backwater valve is located and how to maintain it to prevent basement flooding.

Immediate Actions

  • Contact Toronto Hydro Opens in new window to have your power shut off to prevent shock or electrocution in the event that water has risen above outlets, near the electrical panel, etc.
  • If you suspect the flooding could be the result of a sewer back-up, do not use toilets and sinks unless it is absolutely necessary until the issue has been resolved. Any water sent down the drain may end up in your basement.
  • Contact the City of Toronto by calling 311 or visiting 311’s online service request web page to enter a self-service request.
    • City staff will inspect the problem, assess the flooding and attempt to determine the source(s) of the flooding.

Property Damage

  • Call your insurance company as soon as possible and report property damage caused by the flooding.
  • Take photos of damage caused by the flooding and keep receipts from emergency repair or clean-up work.
  • If the flooding is a result of a private blocked drain pipe, leaking foundation walls or poor lot drainage on your property, then you are responsible for repairs and any subsequent damage caused by flooding.
  • You may submit a claim to the City of Toronto.
    • As Toronto Water is not associated or involved in the claims process, your claim will be forwarded to and managed by the City’s insurance adjusters. A letter of acknowledgement will be sent to you.
    • City insurance adjusters will keep the property owner informed of actions and timelines.

Health and Safety Concerns

Be mindful of health and safety with a flooded basement. Homeowners may be exposed to waterborne diseases, corrosive cleaning agents and irritants found in leftover sludge from a flooded basement. Electrical accidents may occur because of contact with water and electricity. If possible, shut off electrical power.

  • Consider hiring a professional cleaning company familiar with cleaning sewage contaminated basements.
  • Keep children and pets out of the affected area until cleanup has been completed.
  • Dress appropriately – wear full-length clothing, gloves, protective eyeglasses, rubber boots and a mask.
  • Stay away from electrical equipment. Have a licensed electrical contractor assess the situation to determine if there are potential electrical hazards.
  • Water could extinguish a pilot light on a gas appliance. If you detect gas, leave the house immediately and contact the gas company.
  • Discard all contaminated items that cannot be washed and disinfected (i.e. textiles).
  • Wash all surfaces with hot water and liquid detergent, rinse and thoroughly dry and ventilate the area.
  • Sanitize walls and floors using a solution of household bleach (mix 1 cup bleach with 5 gallons of water).
  • Remove and discard drywall and insulation that has been contaminated with sewage or flood waters.
  • Wash all clothes worn during the cleanup in hot water and detergent.
  • Discard any packaged or non-packaged food items that may have come in contact with the flood waters.

When a resident experiences basement flooding, they should report the incident to 311. Reporting a call to 311 is important for several reasons:

  • Investigation: The City will dispatch staff to investigate and take steps to diagnose whether the reported basement flooding and/or blocked sewer service line was the result of an issue with the City’s infrastructure requiring the City to take steps to address it.
  • Sewer service line blockages: Multiple properties on the same street may have experienced basement flooding, which may be an indication that the sanitary sewer under the street has a blockage that needs to be cleared.
  • Inspection record: The City creates a record documenting calls to 311 reporting a basement flood and/or a blocked sewer service line, along with the results of the investigation staff have completed. The results of the investigation and the inspection record plays an important role in the City’s third-party claims investigation process.
  • Infrastructure upgrades: The City refers to the information compiled from the number of calls received in an area that may help identify the performance of City infrastructure and/or if an area has a history of flooding. This information will help determine if any future infrastructure upgrades are required in the area.
  • Improves customer service: Reporting basement flooding can assist the City in planning and deploying field staff efficiently, especially during heavy rainfall.

The City employs skilled water service technicians who follow approved municipal practices related to basement flooding and/or blocked sewer service lines. There are several water service technician’s working 24 hours a day; 7 days a week. Each 311 call results in generating a Customer Service Request that includes: the name of the customer, property address, contact phone number and a brief description of the reported issue. The generation of the Customer Service Request triggers the assignment of a water service technician to attend the area and visit the property to investigate the issue.  When the water service technician arrives, they will assess whether the flooding is related to the operation of the City’s infrastructure.

From the initial call to 311, the customer service response time is normally four hours. However, the response time may vary depending on the number of customer service requests being attended to at that time, especially during heavy rainfall. You will be advised if the response time is more than four hours.

Once the water service technician arrives on-site, the investigation of a reported issue and the work necessary to address any identified issue with the City’s infrastructure can take time. Diagnosing issues with below grade infrastructure could involve an assessment of complicated issues with how the drains and pipes on private property have been installed and connect with the City’s infrastructure.  It could also involve an investigation that may require the involvement of other public authorities that have infrastructure below the ground (for example, Enbridge Gas).

Step 1: Investigating the City sanitary sewer (located under the road)

  • The water service technician will first investigate the City maintenance holes on the road, both upstream and downstream, to determine if the sanitary sewer has surcharged. If the sanitary sewer is blocked and has surcharged, the water service technician may create a new work order for emergency flushing (which requires a special crew of City staff) and, if required, undertake closed circuit TV (CCTV). Flushing a blocked sanitary sewer is emergency work and it can take several hours to mobilize the necessary equipment and may include discussing these circumstances with City engineers.
  • If the surcharge has caused a spill of sewage into the environment, there are strict regulatory requirements the water service technician must follow including proper notification to regulatory agencies.
  • City staff will advise the property owner of all actions so they are informed of the process and timelines.

Step 2: Investigating basement flooding

  • If the blockage is not found on the City sanitary sewer under the road, the water service technician will then visit the property (by knocking on the door to speak with the property owner). If the basement has flooded, the water service technician will ask questions about the colour of the water in the basement (clear, muddy, has an odour, etc.), where the water may have entered the property, how long it took for the water recede and any other questions that can indicate the cause of basement flooding. Clearer water is normally a result of overland flow/drainage issues, while muddy water can be a result of a sewer service line and/or sanitary sewer blockage.
  • City staff, after some storms, may undertake a more detailed investigation of the property for the purposes of diagnosing the cause of the flooding. This information is not related to the third-party liability claims investigation process.
  • City staff will not enter flooded basements for health and safety reasons. City staff will only enter onto private property with the property owners permission and if the water service technician feels it is required and/or safe to do so.
  • The water service technician will provide the property owner with information on how to prevent basement flooding and the subsidies available for flood prevention devices.

Communication with the public should not be interpreted as a conflict of interest when filing a claim, or when the City is defending a claim. The City is only giving truthful information that they are aware of in general terms, and every property, or basement flooding incident is different.

Basement Flooding Protection Subsidy Program

The City offers owners of single-family, duplex and triplex residential homes a subsidy of up to $3,400 per property to install flood protection devices.

Basement Flooding Protection Program

The City is taking steps to stop the overloading of the sewer system and reduce basement flooding.

Mandatory Downspout Disconnection

Disconnecting downspouts from the sewer system is mandatory. It can reduce the risk of basement flooding and releasing polluted rainwater into our local waterways.

Preventative Maintenance

The City regularly inspects, cleans and maintains the sewer system to ensure it is in good working order.