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Basement flooding and sewer backup in Greater Montréal

Plumbers for backwater valves, sump pumps and drains.

93 pros in Greater Montréal

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These plumbing and drainage contractors serve Greater Montréal and say on their own websites that they install backwater valves, sump pits or pumps. Two local points before you hire: Montréal requires a backwater valve on basement plumbing fixtures and advises a CMMTQ-member plumber who gives you a certificate of conformity, and Pointe-Claire's PC-3002 grant pays only for work the city approved before it started.

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Not yet verified. We checked each one’s own website for this work, and the licence in the public register where one applies, but we haven’t contacted them yet. How a business gets listed

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What to know in Greater Montréal

  • Montréal's RénoPlex programme (Bloc 3, flood protection) pays $90 per normally closed backwater valve, $600 per valve under an existing slab and $1,600 per building for a new sump pit and pump system, for owners of 1 to 5 dwellings.

    Ville de Montréal (source, opens in a new tab) (in French)

  • By-law PC-3002, in force since 14 July 2026, pays owners of one- and two-unit homes 50% of eligible stormwater work, evaluation included, up to $5,000 per property. Backwater valves, sumps and foundation drains are listed; work starts only after the city's written approval, by an RBQ-licensed contractor or, where the law allows, the owner.

    Ville de Pointe-Claire (source, opens in a new tab) (in French)

  • Laval's By-law L-11870 requires a sealed sump for foundation drains with a permanent pump of at least 2.6 L/s at 3 m of total head, discharging at least 1 m above the street crown, plus a backup pump with its own power supply where pumping is constant (art. 5.05.01 c). Pumps driven by the water main's pressure or flow are banned, which rules out water-powered backup sump pumps (art. 5.05.01 d).

    Ville de Laval (source, opens in a new tab) (in French)

  • On 9 August 2024 radar estimates put 125 to 200 mm of rain on Laval; runoff, sewer backups and overflowing streams hit most built-up areas, 14 pumping stations stopped, and within 15 days the City logged 2,979 claims from residents plus 6,092 more in four grouped insurer notices.

    Ville de Laval, Bureau de la résilience municipale (source, opens in a new tab) (in French)

Before you hire

  1. Hire a plumber licensed by the RBQ for plumbing work, and check the licence number in the RBQ register before you sign.

    Source: rbq.gouv.qc.ca (source, opens in a new tab)

  2. Get at least three written quotes and put the agreement in writing: the work, materials, price and timing.

    Source: rbq.gouv.qc.ca (source, opens in a new tab)

  3. For a backwater valve, ask for a certificate of conformity with the invoice, as Montréal advises.

    Source: Ville de Montréal (source, opens in a new tab)

Questions about hiring in Greater Montréal

What licence should a plumber have for a backwater valve or sump pit?

In Québec, plumbing work needs an RBQ contractor's licence that includes subclass 15.5, Contractor – plumbing. The CMMTQ issues these licences on the RBQ's behalf, so a plumber showing the CMMTQ logo holds the right one. Ask for the licence number anyway and look it up in the RBQ's licence register before you sign: the listing shows the subclasses and the company providing the financial guarantee. rbq.gouv.qc.ca (source, opens in a new tab)

What should a written quote include?

The Office de la protection du consommateur says the estimate should describe the work and the materials, give the total cost with detailed items, set out the payment terms and give start and end dates. The contract should add the licence number and any permit numbers, the contractor's liability insurer and policy number, and a commitment to follow municipal rules and the building code, with the estimate attached. opc.gouv.qc.ca (source, opens in a new tab)

How do I compare quotes?

The RBQ suggests asking at least three contractors for quotes, and asking each for customer references. Then compare like with like: the same number and type of valves, the same pump and pit work, and the same repair of the floor slab afterwards. Check each licence in the register, and put any verbal promise in writing, as the RBQ advises for every agreement with a contractor. rbq.gouv.qc.ca (source, opens in a new tab)

Is a backwater valve required around Montréal, and is there help with the cost?

In Montréal, yes: the City requires a valve on basement plumbing fixtures, has required them in all new buildings since 2011, and advises keeping the plumber's certificate of conformity with the invoice. Other municipalities, such as Laval with By-law L-11870, set their own rules. Montréal's RénoPlex and Pointe-Claire's PC-3002 help pay for valves and sump work; apply before any work starts. Ville de Montréal (source, opens in a new tab)

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