How sewer backup insurance works & why you need it

This post was first published on February 8, 2021, and was updated on April 9, 2025.

Severe storms are becoming more and more frequent, and the costs are adding up for Canadians. According to the Insurance Bureau of Canada, severe weather broke a record in Canadian history last year, causing $8.5 billion in insured losses. Of the total, hailstorms and flash floods caused significant damage.

As aging sewer systems are asked to deal with increasingly severe storms, sewer backups are a growing concern. But you may be surprised to learn that your home insurance policy may not cover you for this nasty hazard.

With that in mind, let’s look at what causes a sewer backup, how to prevent it, early warning signs, and how home insurance will (or won’t) cover you.

What is a sewer backup?

Sewer backup is when wastewater flows back into your house from the city’s main sewer lines. The sewage typically seeps up into your basement through your floor drains.  A sewer backup can also occur when there is a blockage in your plumbing or sewage systems.

What causes a sewer backup?

There are many ways a sewer can back up into your home, including:  

• Heavy rains or melting snow overflowing the city’s main drains
• A failed sump pump (e.g. power outage, no backup battery)
• Aging sewer systems or lines that have broken or collapsed (e.g. clay pipes)
• Cracked or deteriorating city lines (e.g from tree roots)
• Blockages in city sanitary lines or plumbing inside your home

Are there signs that you may be at risk of a sewer backup?

Yes, when you know what to look for, there are signs a potential sewer backup could be on the way. You should call a licensed plumber if you see any of the following in your home:

• Basement toilet backing up
• Sewage backup in bathtub
• Sewage backing up in basement drain
• The toilet won’t flush after rain and plunging doesn’t help
• Foul smell from drains
• If your toilet or sink “bubbles” more than once
• Back to back toilets clogged
• Several plumbing fixtures drain slowly (or are clogged)
• The washing machine doesn’t drain or backs up into the toilet or bathtub

How do you prevent a sewer backup in your basement?

Homeowners can take several steps to reduce the risk of sewer backups in their basements. We recommend following our guide below to help prevent a sewer backup from occurring.

What not to flush down the drain line

Avoid putting certain items down your drains that could cause a clog. This includes regular household items like cooking oil. Here’s a comprehensive list of what to avoid:  

• • Coffee grinds: Instead, put them in a green bin or your garden.
  • Grease: Do not pour grease down the drain. For bacon grease, fats, or cooking oils, use a separate container until it congeals, then wipe it up with a paper towel and put it into the green bin or the garbage. 
  • Wipes: Don’t flush paper towels, wipes (even if it says they’re flushable), diapers, cigarette butts, or feminine products down the toilet. Use a garbage can or designated discard bin instead.
  • Improper garbage disposal use: To avoid a clogged disposal, run water before and after use to wash food waste away.

Direct water away from your house

Even if you follow proper disposal, a sewer backup is still possible. In this case, you want to ensure water doesn’t have an entryway into your home. Here’s a list of strategies to keep water away:

• Downspout location: Ensure downspouts are at least three feet away from your house (ideally six feet).
• Landscaping choices: Avoid non-porous landscaping (e.g. concrete, asphalt) and use grass or flower beds instead.
• Catching water: Consider using rain barrels or french pits.
• Disconnecting: Ensure your downspouts and weeping tiles are not connected to the city main drain.

Install a backwater valve

A sewer backup valve is like a toilet back-flow prevention device. It’s a plastic box that attaches to your main underground drain and goes to the city's main drains. Typically, this box operates just like an extension of your drain. If the city main drain backs up, you’ll be happy knowing you’re protected. When enough water flows into your house, the sewer backup valve lifts up, preventing water from flowing in or out.

A sewer backup valve should have an access point under your basement floor. If you’re in your basement, think about where all your bathrooms are – the back-flow preventer will be between the bathroom closest to the street and the street itself. 

Many Canadian cities offer subsidy programs to offset the cost of installing a backwater valve and/or sump pump in your home if you’ve had sewer backups in the past or live in a high-risk area. Here are a few of the programs offered by some of Canada’s largest cities.

Get a sump pump installed

A sump pump sucks in water into a sump pit and shoots it out into the soil below the basement. If you live in a low-lying area where you’re at high risk of flooding, it can be a lifesaver. Check them regularly, as they typically last 10-15 years. A sump pump is part of a larger system that includes weeping tile and often a french drain. 

Check your sewer drains

To get ahead of potential problems, you can have a professional plumber perform a sewer line video inspection to check for things like tree roots, cracked pipes, and obstructions. The plumber can also “snake” your drain to clear them out and look for holes or obstructions like tree roots. The cost of these services ranges from $100 to $500, not including the cost of repairs.

What do you do when your sewer backs up?

If sewage backs up into your basement, leave your home as soon as you can. The smell is awful and is toxic to your health. Here are a few things you should be aware of:

• Do not attempt to enter floodwater, especially if there are electrical outlets nearby.
• Don’t use any plumbing fixtures like sinks, bathtubs, or toilets until you’ve called a plumber. 
• If you can, turn off the main power via the electrical panel. 
• Contact your municipality to report the problem and to help determine its cause. 
• Once it’s safe to do so, call a plumber to install a sewer backup valve or back-flow preventer to prevent this problem from happening again. 
• Ask the plumber to “snake” the drain. Snaking a drain clears blockages and prevents items from getting lodged in the drain - either from being improperly flushed down the toilet, an inadequate slope on your pipe, or a crack in clay piping. 
• If your drains are clay, you should strongly consider replacing them with ABS pipe, as it can handle the extreme cold and is more resistant to shock. 
• If you have a sewer backup endorsement on your home insurance policy, you’ll also want to call your insurance company to submit a claim and get the mess cleaned up as soon as possible–including any repairs to your floor, carpets, furniture, baseboards, and drywall. 

Does home insurance cover sewer backup insurance?

Standard home insurance policies in Canada do not include coverage for sewer backup, but you can add it as an optional endorsement. Given the rise in flood insurance claims, many insurance brokers will quote sewer backup by default – ask for it if not – but most companies still charge extra. 

The cost of sewer backup insurance depends on your provider and the age and location of your house. However, it typically ranges from $150 to $300 per year.

Note that having sewer backup insurance doesn’t replace proper maintenance. Even with coverage, you still need to ensure your sewer drains are clear and in good condition for insurance to apply.

Is sewer backup insurance worth it? 

Yes, sewer backup insurance is well worth the cost. The reality is that sewer backups happen, and the cost of repairs and restoration can easily be in the tens of thousands of dollars.

Common expenses include:

• Removal of sewage and water from the home
• Removal and replacement of damaged furniture, appliances, flooring and drywall
• Cleaning and disinfection of the affected area
• Repairs to sewer lines 

In all, experts estimate the cost of a sewer backup to be between $7 and $14 per square foot of the affected area with most occurrences costing between $2,000 and $10,000 – although it’s not unheard of for the cost to reach $50,000 or more. It’s recommended to take out a minimum of $100,000 in coverage.

How much does sewer backup insurance cost?

The average cost of adding sewer backup coverage to your insurance policy is between $150 and $300 per year. But it depends on where you live. In an area with a high frequency of claims, the yearly cost can be as high as $700.

If you don’t have a sewer backup valve or back-flow preventer installed, adding sewer backup coverage to your home insurance policy will help cover potential damage costs.

Do you need sewer backup coverage in a condo?

If you live in a condo and have condo insurance, remember that your policy doesn’t automatically include a sewer backup endorsement. You may wonder why you’ll even need it–don’t your condo fees pay for the building’s insurance and maintenance?

While that’s true, if there’s a blockage because a neighbouring unit above flushed something down they shouldn’t have, and all the units continue flushing down to that blockage, the excess water will look for a place to escape. The escape will be your bathtub, sinks, toilets, or any unit just above the blockage. The damages to your unit and personal contents can be extensive, which can exceed the limits of coverage offered under your building’s policy.

This is why having a condo insurance policy with the right coverages, including contents insurance and sewer backup, is crucial. Just because the building has insurance doesn’t mean it covers damage to individually owned units and the replacement of contents. You are responsible for your designated square footage and belongings.

What about basement apartments?

If you’re renting, tenant's insurance protects your belongings and covers the cost of living elsewhere while the repairs are ongoing. However, your landlord’s insurance won’t protect your stuff. A landlord’s insurance policy will only repair the damage to the unit; your valuables and the cost of living elsewhere are on you, the renter. 

Also read: How tenant insurance helps landlords and tenants lower their risk

The bottom line

Sewer backup risks are real in Canada and can lead to costly repairs. To avoid paying out of pocket, call your home insurance company to see how much it would cost to add sewer backup insurance to your policy. The higher the quote, the more likely you’re in an area with high risk. If you still opt against adding sewer backup coverage, install a sewer backup valve and a sump pump as soon as possible to protect your home from flooding.

Also read

• Overland water coverage – an overview 
• Are you committing home insurance fraud?
• Do you need home insurance for a renovation?