Backwater valve in St. Catharines: the FLAP rules, permit, and code.

A backwater valve alone does not qualify

This is the rule a homeowner searching for backwater valve rules in St. Catharines most needs to know and least expects. Installing a backwater valve on its own is not enough to receive the FLAP rebate. The City's own Emergency FLAP FAQ addresses this directly:

The City's Emergency FLAP Homeowner Information document states the requirement more generally: to receive a rebate, the homeowner must demonstrate that weeping tiles or other stormwater connections, such as downspouts, are not connected to the sanitary sewer system.

Three ways to meet the weeping-tile requirement

Per the City's Emergency FLAP Homeowner Information document, a homeowner can demonstrate the weeping tile and stormwater connection requirement in one of three ways:

• Disconnecting weeping tiles from the sanitary sewer and reconnecting them to a sump pump system. This is itself an eligible expense under the Emergency FLAP.
• Providing documentation that the weeping tiles were previously disconnected.
• Providing documentation that there are no weeping tiles or stormwater connections connected to the sanitary lateral, such as a CCTV or camera inspection.

The City's FAQ explains why the gate exists at all: a backwater valve on its own only helps with basement flooding caused by a sewer surcharging event. It does nothing for overland or infiltration flooding, and it does nothing to fix a weeping tile still tied into the sanitary sewer. Source: City of St. Catharines Emergency FLAP Homeowner Information and FAQs (both PDF, revised 2026-08-26).

What the FLAP pays, and its funding status

The Emergency FLAP reimburses up to 90% of eligible costs, to a maximum of $5,000 per property, the same cap and coverage rate as the standard FLAP described on the main St. Catharines FLAP guide. The program is open and, as of late August 2026, funded. Per the City's own Emergency FLAP page: "At its August 26, 2026 meeting, St. Catharines City Council approved $20 million in funding for the Emergency Flood Alleviation Program." The City's own Council Report EFES/FMS-125-2026 lists its meeting date as August 24, 2026, so there is a two-day gap between the report's own front matter and the City's current live page. This guide follows the City's live page as the current statement, since it is what a homeowner reads today.

Funding approval does not guarantee any individual application. The City states plainly that "completing eligible work does not guarantee reimbursement" and that "early application does not guarantee funding," because reimbursement depends on funding available at the time an application is reviewed. Applications are reviewed in the order they are received; there is no stated deadline or waitlist.

The eligible valve, and why the exclusions exist

The Emergency FLAP's eligible-works list names the valve type precisely: "Mainline backwater valves (normally open)." The City's Emergency FLAP Homeowner Information document excludes two valve types by name: exterior backwater valves, such as an Adapt-a-valve, and normally closed backwater valves.

That is not an arbitrary program choice. It tracks the Ontario Building Code directly: a backwater valve installed in a building drain must be a normally open design, and it may not serve more than one dwelling unit. An exterior device sits outside the building drain rather than in it, and a normally closed design is not the permitted type. Both are excluded because the Code does not permit them in that location, not because the City picked favourites.

The Ontario Building Code rule behind it

The current Ontario Building Code is the National Building Code of Canada 2020, as amended by the Ontario Amendments to the National Building Code of Canada 2020, dated July 17, 2026 and issued by the Ministry of Municipal Affairs and Housing (MMAH), together adopted as the building code by O. Reg. 163/24. The backwater valve rule is Division B, Article 7.4.6.4, "Protection from Backflow." Quoted directly:

• (1) Except as permitted in Sentence (2), a backwater valve that would prevent free circulation of air shall not be installed in a building drain or in a building sewer.
• (2) A backwater valve may be installed in a building drain provided that (a) it is a "normally open" design conforming to CAN/CSA-B70, CAN/CSA-B181.1, CAN/CSA-B181.2, or CAN/CSA-B182.1, and (b) it does not serve more than one dwelling unit.
• (3) Except as provided in Sentences (4) and (5), where a building drain or a branch may be subject to backflow, (a) a backwater valve shall be installed on every fixture drain connected to it when the fixture is located below the level of the adjoining street, or (b) a backwater valve shall be installed to protect fixtures which are below the upstream sanitary manhole cover when a residential building is served by a public sanitary sewer.
• (4) Where more than one fixture is located on a storey and all are connected to the same branch, the backwater valve may be installed on the branch.
• (5) A subsoil drainage pipe that drains into a sanitary drainage system that is subject to surcharge shall be connected in such a manner that sewage cannot back up into the subsoil drainage pipe.

Source: O. Reg. 163/24, s. 1, and the MMAH-issued "Ontario Amendments to the National Building Code of Canada 2020," dated July 17, 2026, cross-checked word for word against the same article in O. Reg. 332/12 (retrieved directly from the Ontario e-Laws API). See the regulation at ontario.ca/laws/regulation/240163. The amendments document itself is not hosted at a stable ontario.ca link and is cited here from a third-party mirror, codenews.ca, dated to match the regulation.

New construction, retrofits, and semi-detached homes

For new construction, Article 7.4.6.4(3) is the trigger: a backwater valve is required wherever a fixture sits below street level, or, for a home on a public sanitary sewer, below the upstream sanitary manhole cover. In practice that covers nearly every basement fixture in a sewered St. Catharines neighbourhood, which is why, per the City's own Council Report: "Backwater valves have been installed on new construction since 2012."

For an existing home, nothing in the Building Code compels a retrofit. The Code governs construction; the requirement attaches when plumbing work happens under a permit, not to a house standing untouched. That is the honest reason a pre-2012 St. Catharines home installs a backwater valve: the FLAP rebate is the reason, not the Building Code. Pre-2012 homes are exactly the group the program targets, and exactly the group the Code never reached.

Semi-detached homes have their own rule. Per the City's own Council Report: "For semi-detached properties, the Building Code requires both properties to have backwater valves; otherwise, there is risk one side could flood the other." This follows directly from 7.4.6.4(2)(b): a normally open valve may not serve more than one dwelling unit, so each side of a semi needs its own.

Pre-approval, and what happens if you start early

The Emergency FLAP process runs in a fixed sequence, per the City's own Council Report and Emergency FLAP page:

• Apply online.
• The City forwards the program's terms and conditions.
• A contractor completes an assessment and provides a quote.
• The homeowner applies for the Plumbing-Only permit.
• The City issues the permit.
• The work is completed.
• A final plumbing inspection is completed.
• The paid invoice is submitted, after the permit is closed.
• The City reviews the claim and issues the rebate.

Starting the work before the permit is in place has a real consequence, stated by the City in its own words rather than as a blanket disqualification: the property owner is required to obtain the permit retroactively, a process that "may involve additional fees, inspections, excavation, camera assessments, or the exposure or removal of completed work to verify compliance with applicable codes, standards, and general permit requirements." All of those costs, the corrective work, and any delay are the property owner's own responsibility. Per the City's FAQ: failure to obtain the required permit "will affect the eligibility of the work and associated costs for Emergency FLAP funding."

Permit and the 2026 fee

A Plumbing-Only permit is required for the work, and the City's online permit portal has a dedicated line for it: "Plumbing only permits (including Emergency FLAP)." Per the City's Rates and Fees By-law 2023-137, the 2026 Minimum Plumbing Permit Fee is $284.10, with additional charges of $31.65 per fixture, $1.42 per linear foot for drain, sewer, or water pipe 4 inches or less, and $2.01 per linear foot for pipe larger than 4 inches, depending on the scope of the job. Which exact line items apply to a given backwater valve job is the City's call to make, not a fixed number this guide can state with certainty. The City's own rates schedule also lists a separate "Backflow Prevention Device" fee that carries the identical $284.10 figure for 2026, so the practical floor is the same either way.

The permit cost is itself an eligible, reimbursable expense under the Emergency FLAP, alongside the contractor's initial assessment. The owner or contractor pays the permit fee up front; it comes back as part of the rebate once the claim is approved.

What this actually costs

The City does not publish a typical or average installed cost for a backwater valve, and this guide will not invent one. What the City does publish is the reimbursement math: 90% of the actual invoiced eligible cost, up to $5,000. Worked forward, that means a job needs roughly $5,556 in eligible costs to reach the full $5,000 cap; below that, the homeowner receives 90% of whatever the eligible work actually costs. That is arithmetic on the City's own published figures, not a cost estimate for this market. The City's own advice: "Homeowners may choose any qualified plumber and are encouraged to obtain competitive quotes."

No extra rebate from the Region or the Province

Niagara Region does not run its own backwater valve subsidy. The Region's own inflow and infiltration page directs homeowners to check with their local municipality, and lists St. Catharines' FLAP alongside three other municipal programs as the actual funded options. The Region's own cost-sharing is with municipalities, not homeowners directly.

There is a live provincial thread worth naming honestly, not as a benefit to stack. Per the City's Council Report, St. Catharines has "commenced discussions" with the Ministry of Municipal Affairs and Housing about having the Emergency FLAP included as an eligible cost under the province's Municipal Disaster Recovery Assistance program, which would reimburse up to 95% of eligible costs. That program, if it proceeds, would reimburse the City, not the homeowner directly, and it is at the discussion stage, not approved. Neither the Region nor the Province adds a separate rebate on top of the City's program today; the $5,000 at 90% is the whole of it.

The rest of the St. Catharines FLAP rules

This page covers the backwater-valve-specific rules: the weeping-tile gate, the eligible valve type, the Building Code behind it, and the permit fee. For the full eligibility gate, the funding backlog, and the rejection-proof document checklist, see the main St. Catharines FLAP guide. If your property is in Niagara Falls, the backwater valve rebate works differently there too; see the Niagara Falls WRAP guide. For every city this guide covers, start at the Ontario Basement Flood Rebate Guide hub.