Sewer Backup Toronto: What to Do Right Now if Sewage is Backing Up in the Basement
If you’re dealing with a sewer backup in Toronto, stop all water use in the house right away, keep people and pets out of the affected area, treat everything the water has touched as contaminated, and switch off power only if it’s safe to do so. For Toronto homeowners and property managers facing a plumbing emergency, 2plumbers can confirm what you’re seeing, help you document the damage, and connect you live to a licensed plumber from our network who can determine whether the blockage is on your side or the City’s sewer. This guide explains the immediate steps to take, how sewer backups are diagnosed, common causes of blockages, when professional repair is needed, what cleanup and insurance steps to expect, and why acting quickly matters to limit health risks, property damage, and delays in getting the right fix.
What to do, in order
Stop using water everywhere in the house
No flushing, no showers, no dishwasher or washing machine. Every litre you send down can send wastewater back up through toilets, sinks, or the lowest drain until the line is clear.
Keep everyone out of the water
Sewage carries bacteria, and grey-looking water from a floor drain should be treated as contaminated water. Keep children and pets upstairs, and do not wade through it in bare feet or ordinary shoes, since tracking it through the house can increase the risk of property damage.
Switch off power to the basement if you can do it dry
If water is near anything that uses electricity, including the furnace, water heater, freezer or any outlet, turn off those circuits at the breaker panel, but only if you can reach the panel without stepping in the water.
Take photos of water damage, then leave it
Your insurance company will want to see the extent before anything is cleaned. Do not start bailing or scrubbing until the plumber has been and the cause is known, since an early professional assessment helps prevent further damage before any cleanup starts.
Call us
Our assistant confirms what is backing up and your postal code and connects you live to a licensed plumber from our network for prompt service. Fast action can help limit costly repairs. Say whether it started during heavy rain, and whether neighbours have the same problem; both point toward the City's sewer.
Report it to Toronto 311 as well if rain is involved
If the backup began during a storm or periods of heavy rainfall, or more than one house on the street is affected, the City's sewer may be surcharging. The plumber's camera will confirm whether the fault is on private property or on the city side; 311 takes the report either way, and understanding city responsibility helps if repairs or claims are needed with the City of Toronto.
Call a professional immediately if…
- Sewage is rising and does not stop when everyone stops using water.
- Backups can occur anytime and should be treated as urgent, whether the City's sewer may be surcharging or there is a problem elsewhere in the wider sewer system.
- More than one drain or fixture is backing up at once, which can point to a sewer blockage.
- The water is near the furnace, water heater or electrical panel.
- Anyone in the house has been in contact with the water and has cuts or open skin.
- You smell natural gas as well as sewage. Leave the building and call Enbridge Gas at 1-866-763-5427 first.
- Once the immediate cause is diagnosed, a plumber can advise whether a backwater valve makes sense to help reduce reverse flow during heavy rainfall.
What happens once you call
The plumber will assess the plumbing system, clear the blockage from the main cleanout and, in most cases, run a camera down the line to identify a blocked sewer or damage along the sewer line, including the common causes and other common offenders behind a sewer blockage: tree roots, debris, grease from the kitchen sink and improper disposal of grease, cooking grease, paper products, or dental floss, and flushing non-biodegradable items can clog the line; damage in older homes with cast iron that may need replacement with plastic pipe; movement from dirt around the line; structural defects from freeze-thaw cycles and ground movement; or a collapsed section, a bellied pipe, or a clear pipe to the property line, where homeowners are typically responsible for issues on the sewer lateral up to that point, which means the fault is the City's if the line is clear beyond it. Depending on what the camera shows, the plumber may use a drain snake to clear a localized clog or wash the line to remove buildup and roots, and hydro-jetting may be used for severe blockages. You will see the footage and hear the options before anything more is done, including whether to install a backwater valve or sump pump for added protection, since sump pumps help redirect groundwater away from foundations.
Cleanup after a sewage backup is a professional cleaning service, not a mop-and-bucket one. Professional sewage cleanup reduces health risks from exposure because trained crews handle sewage safely. Porous materials that were soaked, such as carpet, drywall and cardboard, usually have to go. Your insurer will guide that part; the plumber's report on the cause supports the claim. In some cases, repairs are also needed after water damage.
Questions
Is it my sewer backup or the City's?
From inside you cannot tell. Your pipe is your responsibility to the property line; beyond that it is the City's. A plumber's camera shows whether your section is clear. If it is and water still backs up, or if neighbours flooded at the same time, the problem is on the public side and Toronto 311 handles it.
Why did it happen during heavy rain?
In parts of Toronto with combined or overloaded sewers, a downpour fills the City's pipe faster than it can drain, and water flows backwards into homes through the lowest connection. A backwater valve on your line closes against that flow; the City offers a subsidy program toward installing one.
Can I clean it up myself?
Small amounts, with gloves, boots and disinfectant, once the cause is fixed. A basement that has taken more than a few centimetres of sewage is a job for a restoration company, and most insurers expect you to use one. Take photos first, and do not throw anything out before the insurer has seen it.
How do I stop it happening again in my drain pipes?
If the cause was roots or a damaged pipe, a liner or replacement stops the recurrence. If it was the City's sewer surcharging, a backwater valve is the standard protection, and a plumber can tell you whether your home qualifies for the City's subsidy. Either way, keep wipes and grease out of the drains.