How sewer backups happen and tips for preventing them

When your sewer backs up, sending wastewater into your home, the water damage it causes can be sudden, messy, and costly to clean up. Learning what a sewer backup is (and isn't), what you can do to lower your risk, and what your insurance covers, can help you know what to expect and how to avoid confusion and rushed decisions if you find yourself having to deal with a backup.

A sewer backup occurs when wastewater in your home can't move through the sewer system the way it's supposed to, causing pressure to build up and forcing wastewater  back into your home through floor drains, toilets, sinks or bathtubs. This water is often brown or black due to sewage, but even if it looks clear, if it's coming into your home through an exit pipe, it's still wastewater. 

Sewer backups tend to happen in basements, but that doesn't mean all basement water damage is caused by sewer backups. For example, groundwater seeping in through foundation cracks, surface flooding from heavy rains , and water from a burst pipe are among other types of water damage that are distinct from a sewer backup—and the type of water damage you've experienced can make a difference when it comes to your home insurance coverage.

Sewer backups can be caused by a variety of things, including aging sewer systems, household plumbing issues, and weather-related conditions that overwhelm the system. While some of these causes may be within your control, others are not.

Common causes of sewer backups include:

• Blockages in the main sewer line
• Old or cracked sewer pipes
• Tree root growth
• Sump pump failures
• Power outages
• Heavy rainfall or rapidly melting snow
• Municipal sewer system issues

Older neighbourhoods with a combined sewage and stormwater system can be particularly vulnerable to extreme weather conditions—but even newer, non-combined systems can struggle during severe weather. And with climate change causing more extreme weather events, this means you may be dealing with a sewer system that's pushed harder and more frequently—something which, unfortunately, you can't control as a homeowner. 

While you won't be able to eliminate the risk of a sewer backup completely (especially since there are some risk factors that are beyond your control), there are several practical steps you can take to lower the chances of a sewer backup happening in your home. For example:

• Install a backwater valve: Water takes the path of least resistance. If the local sewer system becomes overwhelmed, a backwater valve helps prevent wastewater from taking that path back through the main sewer line and into your home
• Install a sump pump: A sump pump is a good idea, especially if you've had floods in your basement in the past or if you're using your basement as a living or storage space. Be sure to check your sump pump regularly, and add a battery backup if you don't have one already, so it can keep working even if the power goes out.
• Be careful what goes down your drains: Things to avoid include paper towels, hygiene products, grease, food scraps, and wipes (even if they're labeled "flushable"). 
• Keep tree roots away from sewer lines: If trees are planted too close to sewer lines, there's a risk of their roots infiltrating the line and causing a blockage over time. 
• Direct downspouts away from your foundation: This helps reduce the risk of water pooling near your foundation and adding extra strain on the sewer line, increasing the risk of a sewer backup if the local system becomes stressed or overwhelmed.
• Recognize warning signs: Whether it's slow drains, gurgling sounds coming from your toilet, or frequent clogs, monitoring for early warning signs can help prevent a blockage before it becomes serious enough to cause a backup.

Yes, homes with septic systems can also experience backups, especially during periods of heavy rains or flooding. 

Signs to watch out for include slow drains, gurgling sounds, sewage smells coming out of drains or in your yard, and wet patches near the tank and drain field. 

Regular maintenance is key to preventing your septic system from backing up: 

• Have your system regularly inspected and pumped by professionals
• Be careful what you pour or flush into your drains, including any harsh chemicals that might kill off the beneficial bacteria that helps break down waste in your tank
• Keep the area around the tank and drain field protected and undisturbed (for example, don't drive over the area or park vehicles there)
• Reduce your overall water usage
• Run your washing machine throughout the week rather than several times in one day
• Space out laundry, dishwashing, and showers during rainstorms to help reduce strain on the system 

Most standard home policies don't cover damage caused by a sewer backup, so you'll likely need to add on optional water damage coverage to be protected. 

At TD Insurance, for example, our Extended Water Damage Coverage add-on provides coverage for flooding caused by sewer backups and sump overflow. 

Remember, not all water damage is treated the same by insurance policies, so it's important to review your policy details carefully to know what types of water damage you have coverage for, and whether there are any coverage limits. If you're unsure what your policy covers, talk to your insurance provider. They can help clarify the coverage you have and whether you'll need any additional coverage. 

TD Insurance home insurance customers:
Be sure to download the TD Insurance app and register for MyInsurance, so you can easily review your policy details, add optional coverage, or chat with one of our advisors.

Sewage water contains harmful bacteria and other contaminants, so if you experience a sewer backup, safety should be your top priority. 

Steps to take include:

• Keep people and pets away from affected areas
• Avoid any contact with the water
• Do not touch any fixtures that have been exposed to the water
• If it's safe to do so (for example, if you can reach the breaker panel without walking in water), turn off the electricity to flooded areas 
• Open windows and doors to increase ventilation in the area
• Avoid using water in other parts of your home so you don't add to the backup
• Contact a licenced professional experienced in sewer backups to identify and fix the cause of the backup
• Check with your municipality to see if you need to report the backup (for example, the City of Toronto asks residents to call 311 to report blocked sewer service lines). 

Depending on the severity of the sewer backup, you may need to find alternate accommodations while the damage it has caused is being fixed. 

Sewer backups are disruptive, difficult to clean up, and sometimes caused by factors that are beyond your control. Checking your coverage and talking with your insurer can help you understand whether you have the right coverage and what limits or conditions might apply.