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How sewer backup insurance works & why you need it

We make it easy to compare home insurance quotes with sewer backup coverage. See how affordable it is for you to get the best coverage today.

This post was first published on February 8, 2021, and was updated on November 12, 2023.

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 caused $3.1-billion in damage last year, making it the third-worst in the country’s history. In fact, seven of the 10 worst years for storm damage have occurred within the past decade.

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

Signs you may be at risk of a sewer backup

You should call a licensed plumber if you see any of the following: 

  • Basement toilet backing up
  • Sewage backup in bathtub
  • Sewage backing up in basement drain
  • 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 clogged)
  • The washing machine doesn’t drain or backs up into the toilet or bathtub

How to prevent a sewer backup in your basement?

There are a number of things homeowners can do to prevent a backup, and flooding in general to help prevent a sewer back-up from occurring. We recommend following the:

What not to flush down the drain line

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

Direct water away from your house

  • Ensure downspouts are at least three feet away from your house (ideally six feet)
  • Avoid non-porous landscaping (e.g. concrete, asphalt) and use grass or flower beds instead
  • Consider rain barrels or french pits
  • 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 out to the city main drains. Normally, this box operates just like an extension of your drain. If the city main drain backs up, though, you’ll be happy knowing you’re protected. When enough water flows into your house, the sewer backup valve lifts up preventing any 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 to 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's a few things you should be aware of:

  • Do not attempt to enter the floodwater, especially with 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 avoid this problem from happening in the future. 
  • Ask the plumber to “snake” the drain. Snaking a drain is the process of clearing a blockage from any drain from something getting lodged in the drain – either from something improperly being flushed down the toilet, an inadequate slope on your pipe, or a crack in clay piping. 
  • If your drains are made of clay, you should strongly consider having them replaced 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 insurance policy, you’ll also want to call your home 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 insurance cover sewer backup?

Standard home insurance policies do not include coverage for sewer backup, but you can choose to 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 for it. 

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

Note that having sewer backup insurance doesn’t take the place of proper maintenance. Even with coverage, you still need to make sure your sewer drains are kept clear and in good condition for insurance to apply.

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Is sewer backup insurance worth it? 

Sewer backup insurance is well worth the cost. Sewer backups do 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-$300 per year. But, it depends on where you live. In an area with a high frequency of claims (such as Black Creek and Eglinton in Toronto), the yearly cost can be as high as $700 annually for a Toronto home insurance policy.

If you don’t have a sewer backup valve, or back-flow preventer installed you should add sewer backup coverage to your home insurance policy to help cover the costs of a flooded basement.

Do you need sewer backup coverage in a condo?

If you live in a condo and have condo insurance, just be mindful that your policy doesn’t automatically have this endorsement on your policy. You may even be wondering why you need it, doesn’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 all day forever flushing down to that blockage, well, the excess will look for a place to escape. The escape will be your bathtub, sinks, and toilets or whatever unit is 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 it’s crucial to have a condo insurance policy with the right coverages, including contents insurance and sewer backup. So just because the building itself 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 contents.

What about basement apartments?

If you’re renting, tenant’s insurance protects your stuff and covers the cost for you to live elsewhere while the repairs are ongoing. Your landlord’s insurance doesn’t protect a renter’s belongings. A landlord’s insurance policy will repair the damage to the unit, but your valuables and the cost to live elsewhere is on the renter to replace. 

The bottom line

Call your home insurance company to see how much it would cost you to add sewer backup insurance to your policy and ask about contents limits. The higher the quote, the more likely you’re in an area with high risk. If you still opt against the addition of sewer backup coverage, be sure to get a sewer backup valve and a sump pump installed as soon as possible.

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