In the city of Montréal, yes. The RénoPlex programme (Bloc 3) pays set amounts for flood-protection work in buildings of 1 to 5 dwellings, including $90 per normally closed backwater valve, but only if your application is approved before the work starts. Pointe-Claire pays half of eligible work up to $5,000 under By-law PC-3002. Laval and Longueuil both require valves, and we found no subsidy on either city’s site.
Greater Montréal is several separate cities, and each writes its own sewer rules. This guide covers four of them: the Ville de Montréal (its boroughs), Laval, Longueuil and Pointe-Claire. It sets out what each one requires and what help with the cost each one offers, as their own pages and by-laws described it when we read them in November 2026. Amounts and conditions change, so check the official page linked in each section before you apply. For the pumps that go in the pit, see every sump pump we compare and our flood protection guides.
For the rest of a basement’s flood protection, see the flooding page.
What a backwater valve does
A backwater valve (in French, clapet antiretour) sits on a drain pipe and lets water flow one way only: out of the house to the sewer. When a heavy storm fills the municipal sewer and it starts to push back up the pipes, the valve’s flap closes and keeps that water out of your basement fixtures.
The kind the cities ask for is the normally closed valve: the flap stays shut and opens only to let your own drain water out. Laval’s by-law allows only this type, and it is the type RénoPlex pays for. Montréal’s guidance puts a valve on the basement drain of each fixture or group of fixtures (toilet, sink, shower, washing machine, garage floor drain), kept easy to reach, and suggests checking about twice a year that it moves freely and is not blocked. The City also warns about valves fitted in the wrong place, worn out, or hidden behind a new floor, and suggests having a professional confirm you are protected.
A valve stops sewer backup. It does nothing for groundwater rising around the foundation; that is the job of the foundation drain, the sump pit and its pump, which the same rules also cover (see where the sump pump fits below).
The rules, city by city
Ville de Montréal
Montréal says backwater valves on basement plumbing fixtures are required by its municipal by-law, and it stresses them for homes that have already flooded or had a sewer backup. Since 2011 they have been required in all new buildings in the city. The City advises hiring a plumbing contractor who is a member of the CMMTQ (the Québec master pipe-mechanics’ corporation) and asking for a certificate of conformity with the invoice. (Ville de Montréal, backwater valves, updated 15 July 2025.)
Laval: By-law L-11870
- Backwater valves go upstream of the main collector on every drain branch that sits below the crown of the street. Only normally closed valves are allowed, and no valve of any kind may go on the building’s main collector.
- A floor drain with a built-in safety device, or a threaded plug in the drain, does not replace the separate valve on the branch.
- Valves and cleanouts must stay easy to reach and be cleaned at least once a year.
- The owner must install the by-law’s safety devices, valves and a backup pump among them, and the City is not responsible for damage to a building or its contents when an owner fails to install or maintain them (article 5.05.03).
Sources: By-law L-11870, administrative consolidation (updated 22 April 2025; the City notes that only the adopted text is official) and Laval’s backwater valve maintenance guide.
Longueuil: By-law CO-2021-1141
- Owners must fit a backwater valve on every secondary branch that takes water from plumbing fixtures, floor drains, sump pits and other drains in a basement or cellar or below the crown of the street (article 101), and on branches taking water from low outdoor areas next to the house such as sunken driveways, outside stairwells and French drains (article 102).
- Insert-type (“squeeze-in”) valves are not allowed (article 105). Valves must be PVC, ABS or corrosion-resistant metal, kept accessible and in working order.
- A normally open valve on the sanitary branch is accepted only in narrow cases: a single-family house with a sloped roof, built and plumbed before 28 September 2005, among other conditions (article 104).
- If an owner has not installed compliant valves or kept them working, the City is not responsible for the damage (article 109).
CO-2021-1141 replaced Longueuil’s older valve by-law, CM-2005-382. Source: By-law CO-2021-1141 (the copy on the City’s site; it has since been amended, so check the current version with the City).
Pointe-Claire
Pointe-Claire’s regulations require owners to fit a backwater valve on the service connection to the sewer. The City also suggests checking that the valve is not blocked and cutting back water use during heavy rain or fast snowmelt. (Pointe-Claire, backflow prevention valve.) Pointe-Claire is its own city, so Montréal’s RénoPlex does not apply there; it has its own programme, below.
Montréal’s RénoPlex: what it pays
RénoPlex is the Ville de Montréal’s renovation grant for buildings of 1 to 5 dwellings. Its Bloc 3 funds flood-protection work only. These are the Bloc 3 amounts as the City’s amounts page published them (updated 18 August 2026):
| Work (Bloc 3) | Amount published |
|---|---|
| Normally closed backwater valve | $90 |
| Normally closed backwater valve under an existing slab | $600 per valve |
| New sump pit and pump system | $1,600 per building |
| Roof drain diversion | $3,750 per building |
| Watertight door | $3,500 per door |
| Watertight garage door | $9,750 per door |
| Metal flood barrier at an entry door | $725 |
| Metal flood barrier at a garage door | $1,700 |
Who qualifies and how it works, from the RénoPlex programme page (updated 19 June 2026):
- Building: 1 to 5 dwellings, with a property value at or below $3,860 per square metre. The request must be for at least $500 of grant.
- Approval first: allow 3 to 4 months for confirmation, and wait for it. Work started before approval can cost you the grant.
- Deadline: the work must be done within 18 months of the conditional approval.
- Permits: you still need any permits your borough requires.
- Applying: by the City’s online form, with the documents listed in the programme guide.
Re-read the City’s pages before you apply. Neither RénoPlex page gives an end date for the programme or its amounts. Montréal’s own July 2025 backwater-valve article still shows older, lower figures (and a lower property-value limit), so go by the two programme pages linked above, and check them again on the day you apply.
Tenants: the City tells tenants when a grant is given for their building, and the grant has to be deducted from the cost of the work when rents are calculated.
Pointe-Claire’s By-law PC-3002
Pointe-Claire’s stormwater grant came into force on 14 July 2026. It works differently from RénoPlex: a percentage of the cost, not fixed amounts.
- How much: 50% of the value of eligible work, including the evaluation by the City’s appointed assessor, up to $5,000 per property. Council can change the rate and amounts by resolution and publish them on the City’s site.
- Who: owners of one- and two-dwelling homes. Buildings of three or more units, and non-residential buildings, are excluded. Taxes must be up to date, and the same type of work on the same property must not have been funded in the previous five years.
- What: the by-law’s list includes backwater valves, sumps and foundation drains, internal plumbing from the main drain to the City’s sewer, roof drains, disconnecting downspouts, flood barriers, watertight doors and window wells, among others. Like-for-like replacement and routine repairs do not qualify.
- Before work: apply in writing on the City’s form before anything starts, with a site sketch, a description of the work and at least one quote. Work may begin only after the City’s written approval, which stays valid for 12 months (an extension of up to 6 months can be requested).
- Who does it: a contractor with a valid RBQ licence, or the owner where the law allows.
- Getting paid: claim within 60 days of finishing, with invoices, proof of payment and before-and-after photos. The City pays within 30 working days of a complete claim. When the year’s budget runs out, later requests wait for the next year in the order received.
Source: By-law PC-3002, stormwater financial assistance programme (Ville de Pointe-Claire, adopted 7 July 2026).
Laval and Longueuil: required, but no subsidy found
We looked for a backwater-valve or sump-pump grant on Laval’s and Longueuil’s own sites in November 2026 and did not find one. That is not proof that none exists: programmes open and close, so ask your city’s citizen services before you plan the work. Both by-laws make the owner responsible for having the devices and keeping them working, and both say the City is not responsible for backup damage when they are missing or neglected, so the valve matters even without a grant. Check your home insurance policy’s sewer-backup wording as well.
Where the sump pump fits
The products we compare are only the pump part of this job. The valve, the pit, the drain connections and the paperwork for a grant are a plumber’s work. What the cities say about the pump:
- Montréal recommends an indoor sump pit of at least 600 × 450 × 450 mm (24 × 18 × 18 in) with a pump, and suggests a battery system for the pump, because storms often bring power cuts.
- Laval requires a pump permanently installed in a watertight pit, able to move at least 2.6 litres a second at 3 m of total head, with its discharge line (fitted with a check valve) rising at least 1 m above the crown of the street. Where the foundation drains need pumping all the time, a backup pump with its own independent power supply is required. Laval also forbids using the water main’s pressure or flow as a power source, which rules out water-powered (ejector) backup pumps there (By-law L-11870, art. 5.05.01 c and d).
- Longueuil requires a pump in any pit the by-law calls for (article 89) and makes the owner responsible for one of adequate capacity, in good working order.
Laval’s flow figure is worth checking against a pump’s chart, because 2.6 litres a second is about 41 US gallons a minute. Zoeller’s own chart gives the Zoeller M98 61 gallons a minute at 10 ft (about 3 m), which clears it. The smaller Zoeller M53 is listed at 34 gallons a minute at 10 ft, below Laval’s minimum, though it is a common choice elsewhere. Your plumber should size the pump for your pit, your lift and your city’s rule.
For the battery system Montréal suggests, the Zoeller Aquanot Spin 508 is a 12 V battery backup that sits in the pit beside the main pump and alarms on pump, float, battery and power faults; Zoeller says its wiring and controls should be installed by a qualified licensed electrician. Our battery backup sump pump picks compare it with the alternatives, and battery vs water-powered backup pumps explains why the water-powered kind is not an option in Laval.
Before you call a plumber
- Check your city first. Find out which by-law applies to your address and whether a grant is open.
- Apply before any work. Both RénoPlex and PC-3002 refuse work that started before approval.
- Hire the right trade. A CMMTQ-member plumbing contractor, as Montréal advises; PC-3002 asks for an RBQ-licensed contractor. Ask for a certificate of conformity with the invoice.
- Keep everything. Quotes, invoices, proof of payment and before-and-after photos are what a grant claim needs.
If water is already in the basement, start with what to do first when the basement floods.
Backwater valve questions
How much does Montréal pay for a backwater valve?
RénoPlex Bloc 3 lists $90 per normally closed backwater valve and $600 per valve fitted under an existing slab, according to the City’s amounts page updated 18 August 2026. A new sump pit and pump system is $1,600 per building. The request must total at least $500, and approval must come before the work. Check the page again before applying.
Can I get the grant if the valve is already installed?
Not under the rules as published. Montréal says work started before approval can lose the grant, and Pointe-Claire’s PC-3002 excludes properties where work began before the application was filed. Apply, wait for the written approval, then book the plumber.
Does RénoPlex cover Laval, Longueuil or Pointe-Claire?
No. RénoPlex is a Ville de Montréal programme. Pointe-Claire runs its own grant under By-law PC-3002, and we found no grant on Laval’s or Longueuil’s sites in November 2026. Ask your city directly, since programmes can open after we check.
Is a backwater valve mandatory in Laval and Longueuil?
Yes. Laval’s L-11870 requires normally closed valves on every drain branch below the street crown, and Longueuil’s CO-2021-1141 requires them on basement branches, floor drains and sump pits. Both say the City is not responsible for backup damage when the required devices are missing or not maintained.
Can I install a backwater valve myself?
Montréal advises a CMMTQ-member plumbing contractor and a certificate of conformity, and RénoPlex grants depend on approved, permitted work. PC-3002 allows the owner to do the work only where the law permits; otherwise it must be an RBQ-licensed contractor. Ask your city before you plan to do it yourself.
