My Basement Is Flooding Right Now: What to Do Step by Step
A calm, priority-ordered emergency guide for Toronto homeowners dealing with active basement water
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Introduction
If water is actively entering your basement, you need to act in the right order: protect people first, then stop or slow the water, then protect belongings, then call for help. This guide walks you through each step. Do not rush into standing water without reading the safety section first. If the water is above a few inches and you have electrical outlets, a panel, or appliances at floor level, there is a real electrocution risk. For emergency plumbing help right now, call 647-784-8448 or book online. Tornado Plumbing and Drains dispatches across Toronto and the GTA.
Step 1: Stay safe (do this before anything else)
Do not walk into standing water if it is near electrical outlets, your breaker panel, a water heater, or any other plugged-in appliance. Water conducts electricity, and the shock risk is real. If water is above the level of any outlet or is near your electrical panel, do not enter the basement. Go to your main breaker panel (usually on the ground floor or outside) and turn off the breaker for the basement circuit. If the main panel is in the flooded basement and the water is near it, do not attempt to reach it. Call your electricity provider (Toronto Hydro: 416-542-8000) and ask them to disconnect power remotely. Once power to the basement is confirmed off, it is safe to enter with rubber-soled boots or shoes. Do not go barefoot. If you smell gas, leave the house immediately and call Enbridge Gas: 1-866-763-5427. Keep children and pets out of the area.
Step 2: Identify where the water is coming from
The source determines what you can do right now: Floor drain backup (water or sewage coming up through the floor drain): this usually means the city sewer is overwhelmed or your main line is blocked. You cannot stop this from the inside. Do not flush toilets, run sinks, or use any water. Close the backwater valve manually if you have one and it did not close automatically. If you do not have a backwater valve, there is no immediate way to stop the inflow. Call an emergency plumber. Wall seepage or window well flooding (water coming through foundation cracks, walls, or window wells): try to divert water away from the house outside if it is safe to go out. Clear debris from window well drains. Place towels or sandbags at the entry points. If you have a sump pump, check that it is running. If it is not running, check the plug, the breaker, and whether the float switch is stuck. Burst pipe or supply line failure (clean water spraying or flowing): find the nearest shut-off valve and close it. If you cannot find the specific valve, shut off the main water valve for the whole house. This is usually near your water meter (often in the basement near the front wall). Turn it clockwise to close. Sump pump failure (water rising in the sump pit and overflowing): check the plug and breaker first. If the pump has power and is not running, the float switch may be stuck. Try lifting the float manually. If the pump is running but water is still rising, the pump may be overwhelmed or the check valve has failed. If you have a battery backup pump, confirm it has activated.
Step 3: Protect belongings (only if it is safe to enter)
Once power is off and you have identified the source, move what you can: Move electronics, documents, photos, and irreplaceable items to the ground floor. Prioritize things that cannot be replaced over things that can. Lift furniture legs onto blocks, bricks, or plastic bins if you cannot move the furniture out entirely. Do not try to save large appliances like washers, dryers, or freezers. They are too heavy, and the contents are likely already damaged if water has reached them. Take photos and video of the water level and damage before you start moving anything. Time-stamped documentation is critical for insurance claims. Photograph the floor drain, the sump pit, window wells, and any visible entry points.
Step 4: Call for help
Emergency plumber: call 647-784-8448 or book online. Tornado Plumbing and Drains provides emergency plumbing service across Toronto and the GTA. We can clear blocked main lines, diagnose sump pump failures, and restore drainage. City of Toronto: if the flooding is caused by a city sewer backup affecting your street, report it to 311 (toronto.ca/311). The city is responsible for the main sewer; you are responsible for the private lateral from your property to the city connection. Insurance: call your home insurance provider as soon as possible. Many policies require prompt notification. Ask specifically whether your policy covers sewer backup (this is usually a separate rider, not included in standard policies). Take photos before and during cleanup. Restoration company: if sewage has entered the basement, professional cleanup is recommended. Sewage water contains bacteria and pathogens that require proper disinfection. A plumber fixes the cause; a restoration company handles cleanup, drying, and mould prevention.
What not to do during active basement flooding
Do not use any plumbing fixtures (toilets, sinks, dishwasher, washing machine) if water is backing up through the floor drain. Everything you flush will end up in your basement. Do not use a regular household vacuum to remove water. Standard vacuums are not designed for water and pose an electrocution risk. Use a wet/dry shop vacuum only if the area is de-energized. Do not pump the basement empty too quickly during a storm. If groundwater pressure outside is high and you remove all the water inside, the pressure difference can crack your foundation or push the floor slab upward. Wait until the rain stops or subsides before pumping the last few inches. Do not ignore the smell. If you smell sewage, the backup is from the sanitary sewer, not just rainwater. This requires professional cleanup and disinfection. Do not delay calling your insurance company. Many policies have a 24 to 72 hour notification window for water damage claims.
After the water stops rising
Once the rain subsides and the water stops entering, the priority shifts to removal and drying: Pump or bail the water out. A submersible utility pump ($100 to $200 at hardware stores) can remove standing water. Discharge it outside, at least 3 metres from the foundation, and away from your neighbours. Run fans and dehumidifiers as soon as the area is dry enough to re-energize safely. Mould can begin growing within 24 to 48 hours in warm, damp conditions. The goal is to get humidity below 50% as fast as possible. Remove wet drywall, insulation, and carpet that was soaked by sewage water. These materials cannot be adequately disinfected and will grow mould if left in place. Cut drywall at least 300 mm (12 inches) above the water line. Disinfect hard surfaces (concrete, vinyl, tile) with a solution of 250 ml (1 cup) bleach per 20 litres (5 gallons) of water. For a complete guide to what comes next, see our post After the Flood: Basement Cleanup, Insurance, and Preventing It from Happening Again.
How to prevent this from happening again
Most basement flooding is preventable with the right combination of devices and maintenance: Backwater valve: prevents city sewer backup from entering your home. Cost: $1,440 to $2,600 installed. City of Toronto rebate covers up to $1,250. Sump pump with battery backup: collects groundwater and pumps it away from your foundation, even during power outages. Cost: $720 to $2,200 installed. City rebate covers up to $1,750. Weeping tile disconnection: if your foundation drains are connected to the sanitary sewer (common in older Toronto homes), disconnecting them and routing to a sump pump prevents the sewer from overwhelming your foundation drainage during storms. The City of Toronto covers up to $3,400 per property for these installations through the Basement Flooding Protection Subsidy Program. See our Toronto Basement Flooding Rebate Guide for the full process. For a preventive assessment, book online or call 647-784-8448.
Basement flooding emergency FAQs
Is it safe to go into a flooded basement?
Only if the power to the basement is turned off at the breaker panel. Water near electrical outlets, panels, or plugged-in appliances creates a serious electrocution risk. If your breaker panel is in the flooded basement and water is near it, do not enter. Call Toronto Hydro (416-542-8000) to disconnect power remotely.
Why is sewage coming up through my floor drain?
During heavy rain, the city's combined or sanitary sewers can become overwhelmed. When the sewer system cannot handle the volume, water backs up through the lowest opening in your home, which is usually the basement floor drain. A backwater valve prevents this by closing the sewer line when backflow occurs.
Should I flush the toilet if my basement is flooding?
No. If water is backing up through the floor drain, do not use any plumbing fixtures. Everything you send down a drain (toilet, sink, dishwasher, washing machine) will end up in your basement because the main line cannot drain to the city sewer.
Will my insurance cover basement flooding?
Standard home insurance in Ontario typically does not cover sewer backup or overland water damage. These are usually separate riders that must be added to your policy. Call your insurer as soon as possible during or after a flood. Document everything with photos and video before cleanup.
How fast can a plumber get here during a storm?
During major storms, all plumbing companies experience high call volume. Call 647-784-8448 as early as possible. We prioritize active sewage backups and situations with electrical risk. While waiting, follow the safety and water-stopping steps in this guide.
Can I pump my basement empty during the storm?
Pump most of the water out, but leave the last few inches until the rain subsides. If the ground outside is saturated and you remove all water inside, the pressure difference can crack your foundation slab or push it upward. Once the storm passes and groundwater levels drop, pump the rest.