Commercial, industrial, institutional and larger multi-residential buildings connected to Toronto’s water supply must have a backflow preventer at the water service. The device must be tested by a certified Cross Connection Control Specialist at installation, within 72 hours of any repair or service, and at least once a year. Results are submitted to the City online, and records must be kept on site for seven years.
Most municipalities across the GTA run similar cross-connection control programs. For property managers responsible for several buildings, backflow compliance comes down to knowing which devices you have, when each one is due and who is qualified to test it.
This guide explains what the requirements mean for property managers and building owners in Toronto and the GTA: which buildings need testing, which devices are used, who is allowed to test, what happens during a test, what to do after a failed test and how to keep a portfolio compliant year after year.
What This Guide Covers
Toronto Backflow Requirements at a Glance
The following requirements come from the City of Toronto Backflow Prevention Program and the Water Supply By-law, Municipal Code Chapter 851.
| Requirement | Toronto rule |
|---|---|
| Who must comply | Industrial, commercial, institutional and Part 3 residential buildings, plus construction sites |
| Device location | Premise isolation, immediately after the water meter and bypass piping |
| Device type | Reduced pressure principle assembly (RP) for severe hazard; double check valve assembly (DCVA) for moderate hazard |
| Testing | At installation, within 72 hours of cleaning, repair, replacement, servicing or overhaul, and at least once a year |
| Tester | Certified Cross Connection Control Specialist, registered with the City before testing |
| Reporting | Submitted online by the tester; the owner and tester receive an email confirmation with the result |
| Records | Kept on site for at least seven years |
| Surveys | When requested by the City; updated at least every five years and within 30 days of any increase in hazard |
What Backflow Is and Why Buildings Need Protection
Backflow is the reversal of the normal flow of water, from a building’s plumbing back into the public water supply. It happens in two ways:
- Backpressure: pressure inside the building rises above the pressure in the city main. Boilers, booster pumps and pressurized process systems can all create it.
- Back-siphonage: pressure in the city main drops, for example during a water main break or heavy firefighting demand, and water is drawn back out of the building.
Either one becomes dangerous when there is a cross connection: a link between drinking water and something that should never reach it. Commercial buildings have many of them:
- Boilers and closed heating loops treated with corrosion inhibitors or glycol
- Cooling towers and chilled water make-up connections
- Fire sprinkler systems, especially those using antifreeze or other additives
- Irrigation systems, hose bibbs and chemical dispensers
- Commercial kitchens, laundries, car washes and process equipment
- Medical, dental and laboratory equipment
A backflow preventer is a mechanical assembly that stops water from flowing backwards past it. Municipalities require them because a single event can push contaminated water into the drinking water that serves every building on the street.
Which GTA Buildings Need Backflow Testing
In Toronto, the Water Supply By-law requires a backflow prevention device for premise isolation on:
- Industrial, commercial and institutional properties
- Part 3 residential buildings under the Ontario Building Code
- Construction sites
Part 3 buildings are generally buildings more than three storeys high or larger than 600 square metres in building area. In practice, that captures most condominium and rental apartment buildings, which is why condo boards and multi-residential property managers receive backflow notices as well as commercial owners.
Schedule 5 of the by-law lists industry sectors and the hazard level assigned to each, which determines the type of device required.
Outside Toronto, most GTA municipalities run their own cross-connection control programs with similar annual testing requirements. Forms, deadlines and submission methods differ, so confirm the current rules with the water provider for each property in your portfolio.
Premise Isolation and Internal Protection
Premise isolation protects the city’s water from the entire building, with one device where the water service enters, immediately after the meter. That is the focus of municipal backflow programs.
Zone and fixture protection protects people inside the building from hazards within it, for example a device on the boiler make-up line or a vacuum breaker on a hose connection. These are required under the plumbing provisions of the Ontario Building Code. A building usually needs both, and both should be in your maintenance records.
Backflow Preventer Types and Hazard Levels
CSA B64.10, the Canadian standard for selecting and installing backflow preventers, matches the device to the level of hazard. The Ontario Building Code requires backflow preventers to be selected, installed and tested in conformance with it.
| Device | How it works | Typical use |
|---|---|---|
| Reduced pressure principle assembly (RP) | Two internally loaded check valves separated by a reduced pressure zone. A relief valve discharges water from that zone if a check valve leaks or pressure starts to reverse. | Severe hazard. Required by Toronto for severe hazard premise isolation. |
| Double check valve assembly (DCVA) | Two independent check valves in series, with test cocks to check each one. | Moderate hazard. Required by Toronto for moderate hazard premise isolation. |
| Double check detector assembly (DCDA) | A DCVA with a metered bypass that detects unauthorized use or leaks. | Fire protection services |
| Pressure vacuum breaker (PVB) | A spring-loaded check and an air inlet that opens when pressure drops. | Zone protection against back-siphonage, such as irrigation |
| Atmospheric vacuum breaker (AVB) | An air inlet that prevents back-siphonage. Not testable. | Individual fixtures and outlets |
CSA B64.10 assigns a degree of hazard to each type of facility. Severe hazard applies where backflow could make the water dangerous to health, and includes facilities such as hospitals, laboratories and car washes. Moderate hazard includes facilities such as hotels, restaurants and schools. Minor hazard covers low-risk connections. In Toronto, Schedule 5 of the by-law sets the hazard level for each sector.
When a building’s use changes, its hazard level can change too, which may require a different device.
How Often Backflow Preventers Must Be Tested
| Requirement | When it applies in Toronto |
|---|---|
| Initial test | When the device is first installed |
| Retest after work | Within 72 hours after the device is cleaned, repaired, replaced, serviced or overhauled |
| Annual test | At least once a year, for the life of the device |
| Backflow survey | When requested by the City: submitted by the date in the letter or within 30 days, updated at least every five years and within 30 days of any increase in hazard |
| Record keeping | Copies of records submitted to the City kept on site for at least seven years |
The annual test is the one most often missed, particularly in portfolios where devices were installed at different times. Tracking every device by serial number and due date, rather than by building, is the simplest way to avoid gaps.
Who Is Allowed to Install and Test Backflow Preventers
Installation
In Toronto, premise isolation devices must be installed by a plumber licensed with the City, and new installations and replacements require a building permit, which is usually obtained by the plumber. The device must be installed immediately after the water meter and bypass piping, with no branch or hose connections in between. RP assemblies cannot be installed below grade in a pit, chamber or vault, and their discharge must go to a sanitary sewer.
Testing
Testing must be completed by a certified Cross Connection Control Specialist. Toronto accepts:
- Plumbers holding a Certificate of Qualification and, for contractors, a City plumbing business licence
- Fire sprinkler fitters holding a Certificate of Qualification
- Professional Engineers in good standing
- Certified Engineering Technologists working under a Professional Engineer, for domestic supply and fire protection systems only
Every tester also needs a current Cross Connection Control certificate (OWWA certificates are valid for five years, ASSE certificates for three) and a test gauge calibrated within the last year. Testers must register with the City before testing, so confirm your tester is registered before booking.
What Happens During a Backflow Test
- Schedule the shutdown. Water to the building, or to the part served by the device, is briefly shut off. Tenants or residents should be notified in advance.
- Inspect the installation. The tester confirms the device type, size, serial number, location and orientation, and checks for leaks or damage.
- Test each component. Using a calibrated differential pressure gauge, the tester checks that each check valve holds and, on an RP, that the relief valve opens at the correct pressure, following the CSA B64.10.1 field test procedures.
- Restore service. Valves are returned to their normal positions and water is restored.
- Tag the device. The test tag records the device history, test date, tester and company.
- Submit the report. The tester submits the result to the City online. The owner and tester receive an email confirmation.
A routine test usually takes less than an hour per device. Buildings with several devices, difficult access or fire protection systems that require coordination with the fire alarm monitoring company may need longer.
What to Do When a Device Fails
A failed test means the device is not reliably protecting the water supply. The usual sequence is:
- Identify the cause, often debris, a worn seal or spring, or a damaged check valve.
- Repair the device with manufacturer parts or, if repair is not practical, replace it. Replacements in Toronto require a building permit.
- Retest within 72 hours of the repair or replacement and submit the new result.
- Record the work in your maintenance history.
Older devices and discontinued models can be hard to source parts for. If a device fails repeatedly, plan its replacement through your capital budget rather than paying for the same repair each year. Our commercial building budget planning guide explains how to separate repairs from capital replacements.
Common Compliance Problems in Commercial Buildings
- Missed annual tests across a portfolio where every device has a different due date.
- Tenant changes that raise the hazard level, such as a restaurant, clinic or lab moving into a retail or office space. The City must be notified of any hazard level change.
- Fire protection devices left out of the testing schedule because they sit on a separate service.
- RP assemblies in pits or chambers, or without adequate drainage for relief valve discharge.
- Thermal expansion that was not addressed after installation. Once a backflow preventer is installed, expansion from water heating can no longer relieve back into the city main, so it must be managed inside the building under Part 7 of the Ontario Building Code.
- Missing tags or records that cannot be produced on inspection.
- Unregistered testers whose results cannot be submitted to the City.
What Affects the Cost of Backflow Testing
Backflow testing is usually priced per device. The main factors are:
- Device type and size: larger assemblies and RPs take longer to test than small DCVAs.
- Number of devices: buildings and portfolios with several devices are usually more efficient to test together.
- Access: devices in tight mechanical rooms or at height take longer.
- Timing: after-hours testing to avoid disrupting tenants or residents.
- Repairs: parts and labour if a device fails, plus the retest.
- Replacement: new devices, permits and any piping or drainage changes.
Combining backflow testing with planned commercial plumbing maintenance reduces separate visits and keeps all records in one place.
Backflow Compliance Checklist
Use this checklist to keep every building in your portfolio compliant:
- List every backflow preventer in each building, including fire protection services, with type, size, serial number and location.
- Record the last test date and the next due date for each device.
- Confirm your tester is a certified Cross Connection Control Specialist registered with the municipality.
- Schedule annual tests ahead of each due date and notify occupants of shutdowns.
- Confirm each result was submitted and keep the email confirmation.
- Keep test reports, tags and survey records on site for at least seven years.
- Review tenant changes for any increase in hazard and notify the City.
- Plan replacements for devices that fail repeatedly or are no longer supported.
- Check thermal expansion control and RP drainage at each test.
Frequently Asked Questions
Is Backflow Testing Mandatory for Commercial Buildings in Toronto?
Yes. Toronto’s Water Supply By-law requires industrial, commercial, institutional and Part 3 residential properties, as well as construction sites, to have a premise isolation backflow preventer and to have it tested at least once a year by a certified Cross Connection Control Specialist.
How Often Does a Backflow Preventer Need to Be Tested?
In Toronto, at initial installation, within 72 hours after it is cleaned, repaired, replaced, serviced or overhauled, and at least once a year after that.
Who Is Allowed to Test Backflow Preventers in Toronto?
A certified Cross Connection Control Specialist who is registered with the City. Eligible testers include licensed plumbers, fire sprinkler fitters, Professional Engineers and Certified Engineering Technologists working under a Professional Engineer. Testers need a current OWWA or ASSE certificate and a test gauge calibrated within the last year.
What Is the Difference Between an RP and a DCVA?
Both use two check valves. A reduced pressure principle assembly (RP) adds a relief valve that discharges water if a check valve leaks or pressure starts to reverse, so it is used for severe hazards. A double check valve assembly (DCVA) has no relief valve and is used for moderate hazards.
Do Condominium and Apartment Buildings Need Backflow Testing?
Most do. Toronto’s requirement applies to Part 3 residential buildings, which generally includes buildings more than three storeys high or larger than 600 square metres in building area.
How Long Does a Backflow Test Take?
A routine test usually takes less than an hour per device, with water shut off for part of that time. Larger devices, fire protection systems and buildings with several devices take longer.
What Happens If a Backflow Preventer Fails Its Test?
The device must be repaired or replaced, then retested within 72 hours of the work, with the new result submitted to the City. Replacements in Toronto require a building permit.
How Long Do We Need to Keep Backflow Records?
Toronto requires copies of records submitted to the City to be kept on site for at least seven years.
Do Fire Sprinkler Systems Need Backflow Protection?
Yes. Fire protection systems connected to the municipal water supply need backflow protection selected according to their degree of hazard under CSA B64.10. In Toronto, certified fire sprinkler fitters registered with the City can test these devices.
Do Other GTA Municipalities Have Backflow Programs?
Most do. Municipalities across the GTA run cross-connection control programs with annual testing, but forms, deadlines and submission methods vary. Confirm the requirements with the water provider for each property.
Book Backflow Testing With Kontrol Buildings
Kontrol Buildings provides backflow prevention and testing for commercial, industrial, institutional and multi-residential buildings across Toronto and the GTA. Our OWWA-certified testers are registered with major municipalities, and our licensed plumbers handle surveys, installation, annual testing, repairs and municipal submissions as one service, with digital test reports submitted the same day.
Repairs and replacements are completed by our commercial plumbing team, with 24/7 response for failed tests and red tag notices, and one point of contact for backflow, plumbing and HVAC maintenance.
Book a backflow test or ask about testing across your portfolio.
- Phone: 1-833-456-6876 — 24/7 emergency service
- Email: service@kontrolbuildings.ca
- Web: kontrolbuildings.ca/contact