Buyer's Guide
Sale Without Legal Warranty in Quebec
On a Centris listing, the mention fits on one line: sold without legal warranty of quality, at the buyer’s …
The basement smells of sewer when it rains hard. The downstairs toilet gurgles while the washing machine empties. On a Montreal plex whose original line has never been touched, those two details often point to the same thing: a sunken section of the main drain, what plumbers here call a ventre de boeuf, literally an ox belly. Here is how it gets confirmed, who pays for what, and what a buyer should demand before signing a promise to purchase.
What a ventre de boeuf is, and what the City recognizes
A ventre de boeuf is a stretch of the drain line that has lost its slope and formed a dip. The water no longer runs, it sits. Solids and grease settle in the dip, the usable diameter shrinks, and the blockage comes back no matter how many times the line is snaked.
No municipal or provincial source publishes a statistic on how common this defect is, or an official definition of the expression, which belongs to the trade’s vocabulary. What is official is that the Ville de Montreal names the collapse of the sewer line among the problems affecting a connection, in its own repair process, and that it requires owners to keep their line in good condition.
The visible signs, and the camera inspection of the drain
What shows up on a visit. The lowest fixture complains first: the floor drain, the basement toilet, the laundry tub. Slow draining, a gurgle in another fixture when a bathtub empties, rings around the floor drain, a smell that returns in wet weather, and above all a seller who mentions a plumber “who comes through once a year.”
What the pre-purchase inspection does not do. It is a visual, non destructive examination: anything buried escapes it, the drain included. What it does cover is set out in our home inspection checklist, item by item. The camera is a separate mandate, and nobody will add it on your behalf.
The right camera, per the City’s own specification. To process a repair request, Montreal requires a video recording made by a plumber who is a member of the Corporation des maitres mecaniciens en tuyauterie du Quebec and holds a licence from the Regie du batiment du Quebec. The report must carry the firm’s RBQ licence number, the date, the observations, a sketch of the drain’s position, the dimensions and the materials, and a signature. The video must show the line all the way to the public portion, with the chainage, the footage reading that tracks the camera’s progress, legible on screen. The drain must have been cleaned before filming. Demand that specification even if you are asking the City for nothing.
How far your responsibility goes, and where the City’s begins
Many buyers assume their responsibility stops at the property line, the way it does for drinking water. For the sewer, in Montreal, that is wrong.
| Portion of the line | Who answers for it |
|---|---|
| Drinking water piping, up to the property line | The owner |
| Sewer connection, beyond the property line, up to the municipal sewer under the street | The owner |
| Municipal sewer under the street, structural defect | The City, under conditions |
The City puts it in black and white: the owner is responsible for the maintenance, the replacement and the repair of the building’s entire sewer connection, beyond the limits of the property, up to the point where it joins the municipal sewer under the street.
When the City does step in at its own expense, it is on cumulative conditions: the work is on public property, the diameter of the line is at most 225 mm for a storm or combined sewer and at most 150 mm for a sanitary sewer, and the defect is structural, a break or a hole. An obstruction, or a problem caused by misuse of the system, is excluded. The work is done from May to November, emergencies aside.
One last point, often discovered too late: a claim to the City for property damage must be filed within 15 days of the event, and the City is not liable for a sewer backup if you did not have a backwater valve in good working order.
Repairing a ventre de boeuf: what actually drives the bill
I am not going to give you a price range. No official source publishes one, and an invented figure would not help you negotiate. What is documented is the items that set the amount.
The permit. It is mandatory for work on water and sewer connections, on public property and on private land alike, and its cost varies from one borough to another.
Public property. A contractor excavating in the street must hold a valid RBQ licence and provide an insurance endorsement naming the Ville de Montreal as a co-insured. The permit amount is paid as a deposit, based on an estimate, then adjusted according to the actual area of public property repaired and according to the season. The difference is refunded or billed within 60 days of the end of the work. Two quotes therefore differ above all by the length to be opened up in the street.
The method. Put the question to the plumber in writing: does the proposed solution correct the slope of the line, or only its watertightness? The two do not cost the same and do not solve the same problem.
If you are building an acquisition budget, add this item to the rest with the closing costs calculator, before the offer and not after.
Backwater valve and grant: what exists in Montreal and in Laval
A ventre de boeuf slows the flow. A backwater valve does something else: it stops water from the municipal sewer from coming back up into your home. Same basement, two separate jobs.
The framework. The Construction Code of Quebec, chapter III, Plumbing, governs protection against backups at its article 2.4.6.4, which sets out the methods, the location and the types of valve permitted. In Montreal, by-law 11-010 on the protection of buildings against sewer backups has required a valve in all new buildings since 2011, on the drainage piping of every basement fixture or group of fixtures: toilets, sinks, showers, washing machine, floor drains. The valve must stay accessible, and the City recommends checking twice a year that it works and is not obstructed.
In Laval. By-law L-5057, at its article 3.03.02, requires valves on every drainage connection receiving water from fixtures located below the crown of the street. It prohibits installing a valve, of any type, on the main collector, and provides that the City is not liable for damage if the owner failed to install or maintain their valves. A floor drain with a built in valve does not excuse installing a separate valve on the connection.
The Montreal grant. It still exists, under a different name: the flood protection component of the RénoPlex program, for buildings of 1 to 5 units whose assessed value is at or below $3,860 per square metre.
| Work | Amount granted |
|---|---|
| Installing a normally closed backwater valve | $90 |
| Installing that valve under an existing slab | $600 per valve |
These are the amounts published by the City as of August 18, 2026, and the flood component requires a grant application of at least $500. The rule that makes people lose the money is elsewhere: you have to wait for written confirmation that your application is approved before starting the work, and you should allow 3 to 4 months to get it.
Montreal also offers a free home inspection to prevent backups, first to people who have suffered one or filed a claim, and to vulnerable sectors. The inspector hands over a report of the corrective work to be done, but the City does not pay for it.
The sewer backup endorsement, and why the base policy is not enough
The basic coverage of a home insurance policy generally covers water damage that starts inside the building. Sewer backup is not part of it: you have to add an endorsement to the contract, often called the ground water and sewer damage coverage. According to the Insurance Bureau of Canada’s information site, the average cost of a sewer backup claim in Quebec exceeded $18,000 in 2023.
Two moves before you buy. Ask your insurer, before the inspection period ends, whether the endorsement is available for this address and on what conditions. Then ask the seller, in writing, whether there has already been a backup and a claim: the answer belongs in the Declarations du vendeur sur l’immeuble, the seller’s declarations form.
What a buyer demands before making an offer on an older plex
- A camera inspection of the drain, separate from the pre-purchase inspection, with visible chainage and a signed report carrying the RBQ licence number.
- The video itself, not just the verbal verdict.
- Is there a backwater valve, on which fixtures, and is it accessible?
- The history: backups, claims, repeated unclogging, work already done on the connection and the permits obtained.
- Your insurer’s position on the endorsement, before conditions are lifted.
If the seller refuses the camera on a building with a finished basement, treat that refusal as information. Reread the red flags that justify walking away before you get attached to the building.
Frequently asked questions
Can a ventre de boeuf be fixed for good? It depends on the cause and the length affected. Have it stated in writing whether the method corrects the slope or only the watertightness, and demand a control camera run after the work.
The seller tells me the drain was unclogged last year. Is that reassuring? Unclogging treats a symptom. If it comes back every year in the same spot, the camera will tell you why. Ask for the invoice: it often states the distance at which the blockage was found.
Can the City pay for my repair? Only if the defect is structural, located on public property, in diameters of at most 225 mm for storm or combined and 150 mm for sanitary, and is not an obstruction. The rest of the connection, even under the sidewalk, belongs to you.
I have a valve. Am I covered by my insurance? Those are two different things. The valve reduces the risk and conditions the City’s liability in a backup. Coverage depends on the endorsement written into your policy.
To round it out, read the home inspection checklist, item by item and the hidden costs of homeownership. If you are aiming at an income property, start with the honest beginner’s guide to plexes.
Unsure whether to order a camera before making an offer on an older plex? Write to me and I will tell you what to put in the promise to purchase to keep the door open.
Georges Matar
Residential Real Estate Broker · RE/MAX DU CARTIER INC.
Contact Georges
