Flooded basement in Ottawa?

The City of Ottawa's advice starts with safety. Do not enter the flooded area until a qualified professional has determined it is safe. Call Hydro Ottawa if the water has reached any plug, electrical outlet, extension cord or electrical appliance, such as a baseboard heater. Call Enbridge Gas if it is threatening gas-fired equipment such as a furnace, hot water heater or stove.

Then find out where the water is coming from, with a test the City publishes. Run a toilet or a sink and watch the floor drain. If water comes up through the drain, the likely problem is on the drain or sewer side. If nothing comes up, the City says the problem is likely ground water.

Stop using sinks, toilets and any appliance that uses water until it is sorted out. The City's reason is plain: any water sent down the drain may end up in your basement.

Find the sewer clean-out caps, but do not open them. The City says they are usually in the basement floor at the front of the house, near the water meter, and asks you to clear at least one metre on every side so its staff can reach them. Do not lift the round iron maintenance hole covers either.

Treat the water as dirty. The City warns that basement flood water may contain sewage, and says to wear rubber boots, gloves, safety glasses and a facemask, and to wash thoroughly after touching flood water or anything it reached. Where the water carried sewage, Health Canada adds, contact your local public health department.

The City's page on the causes of basement flooding lists five. The sewer main under the street can back up into the house when it is blocked, damaged or surcharged by heavy rain or nearby construction, if there is no backwater valve or the valve has not been maintained.

Your own lateral, the pipe from the house to the street, can block with grease, paper, tree roots or a clogged backwater valve.

Spring runoff and heavy rain can leak through cracks or joints in the foundation walls and floor. Overland water, most often from snowmelt and rainstorms, seeps in through windows, doors and cracks. Some areas flood from the river itself, and the City publishes an interactive map of the 1-in-100 year flood plain.

Older streets add a twist. In some older homes the foundation drains connect to the sanitary or combined sewer, or there are none, and in those partially separated and combined sewer areas the City says the basement flooding risk generally comes from that sewer. A newer infill house on the same street may have more modern connections.

The cause matters three ways. It decides who pays to clear a blockage, whether the City's grant applies, and which part of your insurance responds. So report it, even if the water is already gone: the City's report form asks whether the flooding is happening now or is a past event.

Call 3-1-1 or report it online. The City says requests are typically actioned within three hours to decide whether a site visit is needed, and that storms and request volumes change that. If staff come, someone 18 or older has to be home to meet them.

City staff inspect the sewer main near your home, and fix it as soon as possible if it is the problem. If the problem is in your home's own drain system, you will be advised to call a plumber.

If it is in the sanitary or storm lateral, the repair may fall to you, to the City or to both, and the City decides which after staff review all the information.

The property line splits the pipe. The City is responsible for the laterals from the property line to the street, and you are responsible from the property line to the house. A lateral blockage is generally yours, unless City-owned tree roots caused it or the damaged part is on City property.

For a blockage on the private side you can hire a contractor of your choice or use the City's, and a Building Permit may be required.

If the work shows the blockage was on City property, you are not charged, and anything you already paid is reimbursed up to what the City typically pays its own contractor for the same service. Reimbursement requests and damage claims go to the City's Claims Unit at 613-580-2655 or claims@ottawa.ca. The City notes that your insurance company will typically submit a claim to it on your behalf.

The City pays a $1,000 Compassionate Grant to a residential owner or tenant whose basement flooded because the City's sewer surcharged. It is not paid for flooding from an appliance failure, a blocked sewer lateral, or overland water through a foundation crack or a leaking window well.

To qualify, the flood has to have happened after March 1, 2025 and caused more than $1,000 in damage. You must have reported it to the City within one calendar month, online or through 3-1-1, and you apply within one year of the flood. A grant received in the previous five years normally rules you out. A grant application does not count as the flood report, so make both.

For the July 1, 2026 storm the City changed three rules. It extended the reporting period to October 1, 2026, it removed the five-year limit, and it dropped the proof of flood protection work it normally asks of a repeat applicant.

Proof is the part to get right. The City asks for two or more items showing more than $1,000 in damage or costs, and counts several photos as one item, which must come with something else, such as an insurance claim or an invoice. The items it accepts are dated photos of the flooding and the damaged goods, a copy of the insurance claim submission, and paid invoices.

The invoices it lists are for renting or buying a dehumidifier, a wet/dry vacuum, a portable blower or a storage container, and for professional cleaning, appliance repair or replacement, waste disposal or water removal. Keep every one. You also attach proof that you owned or rented the home when it flooded.

Apply online, at any Client Service Centre or the Permit Desk at 951 Clyde Avenue N, or by mail to Compassionate Grant, City of Ottawa, 951 Clyde Avenue N, Ottawa, ON K1Z 5A6. The City's urban flooding questions page lists the grant as under review, so read its page for the current terms before you count on it.

Health Canada's flood clean-up guidance says a house and its furnishings are less likely to grow mould if they are dried within 48 hours. It starts with the power: shut it off to the flooded area at the breaker box, asking the electrical utility for help if needed, and wear rubber boots while standing in water.

Then remove the standing water, everything soaked or dirty, and the debris and mud. Remove and discard water-soaked flooring. Take finished walls out completely if the water was several feet high, or if the walls stayed wet or humid for 48 hours or more. Dispose of furniture and household items that were in flood water and cannot be dried.

Health Canada's mould guide is blunter about soft goods. It says to throw away carpets, sofas, cushions, mattresses, pillows, stuffed toys and bedding that got wet, notes that mould can begin to grow within 48 hours, and says it is not possible to properly clean a mouldy mattress.

Health Canada says to ventilate and dehumidify until the house is dry, keep indoor humidity between 30 and 50 percent, use fans and open windows when the weather allows, and vacuum dried surfaces with a HEPA vacuum. Keep a working carbon monoxide alarm running while you dry, and never run equipment designed for outdoor use inside.

If the house is on a well, Health Canada says not to use the water for drinking, cooking, bathing or brushing teeth until your local health authority has advised on disinfection and testing, and not to switch the well pump on until a certified well contractor has inspected it and its wiring.

Drying is the step that is easy to cut short. The water you can see is the small part: drywall, framing and subfloor hold the rest and give it back slowly.

Our flood cleanup and water damage restoration crew takes out what will not dry, runs air movers and dehumidifiers, and reads the same points daily until they match an unaffected part of the house, then hauls the ruined material away.

Check the policy before you assume. The Insurance Bureau of Canada, the industry association for Canada's property and casualty insurers, says water damage in a basement due to a sewer backup is only covered if you bought specific, optional sewer backup coverage.

Flood coverage is optional too. IBC says it typically covers lakes, ponds or rivers overflowing, surface water from heavy rain or melting snow, and ground water rising so that water enters at ground level or seeps through windows, doors and walls. Groundwater and seepage coverage are not standard on all home policies, and some insurers sell them as optional endorsements.

If the house is unliveable after an insured loss, IBC says standard home policies cover additional living expenses, and that in a flood this applies to people who bought the optional sewer backup or overland flood coverage. Its Consumer Information Centre answers coverage questions at 1-844-227-5422.

The City's advice for the claim is to understand your coverage, photograph and document damaged items, and keep receipts for emergency work, repairs and replacements. If mould has already started, our guide on whether home insurance covers mould in Ontario goes through the claim steps and what to do if a claim is refused.

Mould is what slow drying costs. Health Canada's guide says mould will begin to grow in an area with excessive moisture within 48 hours. It lists two flood situations that need a qualified professional: flood water contaminated with sewage, and flooding that has got into wall, ceiling or floor cavities, where drying out by traditional methods is not possible.

In the weeks after, watch for stains, peeling paint, warped wood, a white powdery crust on the concrete, and a musty smell. Our page on mould removal in Ottawa covers Health Canada's size chart and how containment works. If a smell lingers with nothing to see, our guide to mould testing in Ottawa explains when a test is worth paying for.

The City's Residential Protective Plumbing program pays the lesser of the cost of the work or a maximum per device. The maximums are $1,000 for an indoor sanitary backwater valve, $1,000 for a storm backwater valve and $2,500 for an outdoor storm backwater valve.

A primary or secondary sump pump with battery backup earns $1,500 in an existing pit, or $3,000 if the pit has to be built. It also covers 100 percent of the current Building Permit fee for the plumbing work.

The home has to be in Ottawa and built before January 1, 2004 for a storm backwater valve rebate, or before January 1, 2012 for a sanitary one, and the City cannot have installed the device. You need a Building Permit before the work and a City inspection after it.

Since July 1, 2026, you have 18 months from the permit's issue date, up from 12, to finish the work and apply. Maintenance, repair and replacement of an existing device are not covered, and the City's urban flooding questions page lists this program as under review as well.

The City's prevention page lists them. Seal window wells and cracks, slope the ground away from the foundation, and redirect downspouts to permeable ground 3 metres from the foundation; the City's flooding questions page gives 1.2 metres as the minimum.

The sump pump should discharge to the storm sewer or to the ground at least 1.2 metres from the foundation. Clear snow away from the foundation, and keep grease and garbage out of the drains.

In priority areas, the City's Rain Ready Ottawa program may rebate up to $5,000 for projects like downspout redirection, rain gardens and soak-away pits.

And if you already have a backwater valve, maintain it: the City says to check it periodically or before forecast heavy rain, and warns that in older homes with cast iron pipes, rust can build up at the hinge and stop the valve closing during a surcharge.