Best Flood Protection Tips for Montreal Homeowners – Backwater Valves & Beyond
- monsieurdrainwebsi
- Nov 21
- 7 min read
As record-breaking storms become the new normal and cities acknowledge their systems can’t keep pace, homeowners are left with no choice but to safeguard their homes themselves.
Scientists have been warning us since that Eurythmics song came out in the early ’80s that global warming would lead to more rain. In the ensuing decades, studies and reports increasingly predicted that global warming would intensify and increase the frequency of heavy rainfall events.
So when parts of Montreal were deluged with more than 100 millimetres of rain on July 10, and then another storm dumped about 150 mm only one month later, nobody in the climate science world was surprised. This is the wettest summer on record since 1942, and the trend is wetter.
But thousands of homeowners across the province, many of whom had never experienced flooding before, faced a nasty surprise when their basements and garages took in water during those events. A flooded basement can be a financial and logistical nightmare because everything must be removed, cleaned and dried, or discarded. Soaked floors and wall boards must be removed within 48 hours to keep dangerous mould from growing. It’s a colossal mess that costs money, saps time and takes a toll on the psyche.
Some homeowners are blaming their municipalities and demanding improvements to the storm sewer network. But as Dorval Mayor Marc Doret told The Gazette this week, no city is in a position to rebuild its waterworks infrastructure before the next big storm hits.
“We can’t redo all the sewer networks in the city in the next year. Financially, it’s impossible,” he said, “… And the question, when will the next big storm hit?” He notes Dorval has invested in storm retention basins and plans to do more for the hardest hit areas of his city, but it will take years.
Montreal has invested in 20 underground retention basins to hold massive amounts of water during heavy rains, but still, the city admits its sewer system can’t cope with these unprecedented storms. An additional $390 million will be spent over the next 10 years to update, repair and expand Montreal’s sewer system and the city is also exploring “green infrastructure” solutions, such as building parks and streets in ways designed to absorb runoff.
But flood experts say municipalities need to get the message out to homeowners they can and should take action themselves, and now, to reduce the risk of flooded basements and to lesson the damage if water does get in.
Joanna Eyquem is managing director of climate resilient infrastructure at the Intact Centre, a research arm of the University of Waterloo. She lives in Montreal and also acts as the centre’s director for the Quebec region. It was founded in 2015 with a donation from the Intact Financial Corporation, a property and casualty insurance company, to develop guidelines to mitigate the effects of climate change and extreme weather.
The Intact Centre published a report in 2019 called Water on the Rise: Protecting Canadian Homes from The Growing Threat of Flooding. It reported basement flooding is on the rise across the country because of intense rainfall events, aging municipal infrastructure, loss of natural spaces, and lack of flood protection measures on the household level.
The report outlined the top 10 actions homeowners can take to reduce the risk of basement flooding. Eyquem notes that several of these actions can be completed by residents themselves, in less than a day, and for less than $500. The recommended actions include:
Remove debris from the nearest storm drain to your home
Correct grading around your foundations so water runs away from the house, rather than toward it
Clean eavestroughs and extend downspouts so run-off lands at least two metres from the house
Install window wells and covers
Keep floor drains clear
Don’t store valuables in the basement or put them in watertight containers stored off the floor
Test the sump pump and install back-up power in case of a power outage
“One action that is completely free is to understand how the drainage in your own house works,” Eyquem said. “Do you have a sump pump, for example? Some people don’t even know they have one. Do you have a backwater valve? Some people don’t know where their floor drain is. It might be covered with carpet.”
The centre launched a residential flood risk reduction education program in 2016. They assessed 500 homes in Ontario and Saskatoon from 2017 to 2018 and identified the most common causes for flooding in private homes. They found:
85 per cent of the homes assessed had no backup sump pump or power source
71 per cent had furniture and electronics at risk of water damage
53 per cent of homeowners do not maintain their backwater valve
40 per cent of homeowners never maintain their sump pump
82 per cent had window wells with sides that were less than 10 cm above the ground
78 per cent had downspouts that deposited water less than two meters from the foundation
69 per cent had grading around their home that did not direct water away from the foundation
63 per cent had cracks or gaps in basement windows and frames
Eyquem commended Montreal’s new plan for flood resilience during heavy rains, but noted a big part of every city’s plan needs to be educating homeowners about what they can do to reduce their flood risk.
Expanded Flood-Protection Action List for Montreal Homeowners
Action | Why It Matters | Approx. Cost / Effort |
Clear storm drains & gutters | Prevent clogs that lead to runoff pooling | Low-cost, DIY |
Ensure proper grading | Water flows away from home, not toward it | < $500, simple landscaping |
Extend downspouts ≥ 2 m | Keep roof runoff far from the foundation | ~ $50–100 materials |
Install window wells & covers | Keep stormwater out of the basement windows | DIY or contractor, modest cost |
Maintain floor drains | Avoid blockages and backups | Free, visual check |
Test sump pump, add backup power | Keeps water out even during power outages | <$200 for generator or battery |
Install backwater valve (clapet anti‑retour) | Prevent sewer backup into the basement | $2,000–$3,500 typical retrofits |
Educate yourself on your drainage system | Know what you have and how it works | Free; ask a plumber to assess |
Use tile or vinyl flooring in basement apartments | Easier cleanup after minor flooding | Moderate; part of the renovation budget |
Apply for RénoPlex funding | Financial aid for mitigation upgrades | Up to $20K–$40K per dwelling |
“I am quite happy to see the new strategy, (but there is a big need for public education about) what the risk is and b) what they can do to reduce the risk. Until something happens, a lot of people think it will never happen to them.”
Source:
Frequently Ask Questions
1. How do I know if my home is at risk of flooding in Montreal?
Flood risk depends on location, elevation, drainage, and local infrastructure. Homes in low-lying areas, former creek beds, or near overburdened sewers are at higher risk. You can:
Check if your borough provides floodplain or risk maps
Contact the City of Montreal’s water department
Look for signs like frequent puddles, poor yard drainage, or water stains in your basement
Talk to neighbors or consult a drainage specialist
2. What’s the difference between a backwater valve and a sump pump?
A backwater valve prevents sewage from backing up into your home through floor drains during storms. A sump pump removes groundwater that collects around your foundation and pushes it safely away from your basement. Think of it like this:
Backwater valve = protects from the city’s sewer system
Sump pump = protects from water under or around your home
3. Does the City of Montreal require backwater valve installation?
While not mandatory in all areas, backwater valve installation is strongly encouraged—especially in flood-prone zones. Some boroughs, like Ville-Marie, are introducing stricter rules for basement dwellings. The city also offers financial assistance through programs like RénoPlex, which provides up to $20,000–$40,000 to install flood protection equipment, including backwater valves.
4. How much does it cost to install a sump pump or backwater valve in Montreal?
Costs can vary based on your home and plumbing setup:
Backwater valve: $2,000–$3,500 (including excavation, valve, concrete repair)
Sump pump system: $500–$1,500 (basic), or more with battery backups or dual pumps
You may qualify for subsidies like RénoPlex to offset these costs.
5. Can I install a backflow prevention valve myself, or should I hire a professional?
Installing a backwater valve typically involves cutting into your main sewer line, which requires plumbing expertise and city permits. It’s not recommended as a DIY project. Always hire a certified plumber who can:
Inspect your system
Obtain required permits
Ensure compliance with Montreal’s building codes
6. What’s the best type of backup system for a sump pump—battery or water-powered?
Both have pros and cons:
Battery-powered backup: Reliable, works even during power outages, and easy to install. Needs occasional battery replacement.
Water-powered backup: Runs on your home’s water pressure—no battery needed. However, less effective in low-pressure areas and uses drinking water.
For most Montreal homes, a battery backup is recommended due to reliable performance during blackouts.
7. Should I get a camera inspection of my main drain before flood season?
Yes. A camera inspection can detect:
Blockages
Tree root intrusions
Pipe cracks or misalignments
Doing this before flood season allows you to fix hidden issues and ensures your drainage system is functioning properly—especially if you’ve had slow drains or past flooding.
8. Why is my basement flooding even if I have a sump pump installed?
Common reasons include:
The sump pump isn’t powerful enough or has failed
No battery backup (it stops working during power outages)
Clogged discharge pipe
Water is entering from elsewhere (e.g. sewer backup—needs a backwater valve)
Poor grading, leaky window wells, or unsealed cracks in basement walls/floor
Regular maintenance and combining sump pumps with a backwater valve provides better protection.
9. How often should I clean my garage pit or check outdoor drains?
Check and clean:
Garage pits: At least twice a year (spring and fall), or after major storms
Outdoor drains/storm grates: Monthly, or immediately before/after heavy rain
Remove leaves, dirt, and debris to ensure smooth drainage and prevent water pooling near your foundation.
10. Will my home insurance cover water damage from basement flooding?
Not always. Standard home insurance policies often exclude sewer backup or overland flooding unless you add optional riders. You should:
Check if you have sewer backup coverage
Ask about overland water protection (for surface water entering through walls or windows)
Understand your deductible and limits
Document your home upgrades (e.g. installing a backwater valve) to possibly reduce your premiums.
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