NFPA 291 Step-by-Step Guide (Ontario)
Fire hydrant flow testing is not just about opening a hydrant and measuring water. In Ontario, hydrant flow testing must be conducted using a recognized, repeatable, and defensible procedure, most commonly NFPA 291 – Recommended Practice for Fire Flow Testing and Marking of Hydrants.
This guide explains the NFPA 291 hydrant flow testing procedure step by step, how it is applied in Ontario, and why following the correct method matters for fire protection system design, code compliance, and firefighter safety.
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What Is NFPA 291?
NFPA 291 – Recommended Practice for Fire Flow Testing and Marking of Hydrants is the North American standard that defines:
How to conduct a fire hydrant flow test
How to measure static and residual pressure
How to calculate available fire flow
How to safely discharge water
How to mark hydrants based on flow capacity
In Ontario, NFPA 291 is widely accepted by:
Fire departments
Engineers and designers
Municipalities
Insurance underwriters
It is typically used together with NFPA 25, which defines when hydrants must be tested.
When Is NFPA 291 Used in Ontario?
NFPA 291 procedures are commonly required for:
5-year hydrant flow testing
New construction and site development
Fire sprinkler and standpipe system design
Fire pump sizing
Insurance and risk assessments
Municipal fire flow evaluations
While the Ontario Fire Code does not prescribe test steps, it relies on recognized standards, making NFPA 291 the accepted method.
Overview of the NFPA 291 Flow Test Method
NFPA 291 uses a two-hydrant method whenever possible:
Test hydrant (flow hydrant) – fully opened to discharge water
Pressure hydrant (residual hydrant) – used to measure pressure changes
This method provides accurate and repeatable results.
Step-by-Step Fire Hydrant Flow Testing Procedure (NFPA 291)
Step 1: Pre-Test Planning and Coordination
Before any hydrant is opened, proper planning is required.
This includes:
Identifying hydrant locations
Confirming hydrant ownership (municipal vs private)
Coordinating with the municipality or water authority if required
Ensuring traffic control and public safety
Selecting appropriate discharge locations to avoid flooding or damage
In Ontario, municipalities may require authorization before operating public hydrants.
Step 2: Select the Test and Pressure Hydrants
The test hydrant is the hydrant that will be fully opened and flowed
The pressure hydrant is typically the closest hydrant on the same water main
This setup allows accurate measurement of pressure loss during flow.
Step 3: Measure Static Pressure
Static pressure is measured before any water is flowing.
Procedure:
Attach a calibrated pressure gauge to the pressure hydrant
Record the static pressure (psi or kPa)
Static pressure represents the system pressure at that location with no flow.
Step 4: Open the Test Hydrant and Establish Flow
The test hydrant is then:
Opened slowly and fully
Allowed to flow freely through an outlet or diffuser
Important considerations:
Use diffusers to reduce erosion and damage
Ensure water discharge does not undermine pavement or structures
Maintain safe distance from personnel
NFPA 291 emphasizes controlled, full-flow conditions.
Step 5: Measure Residual Pressure
While the test hydrant is flowing:
Record the residual pressure at the pressure hydrant
Residual pressure is the pressure in the system under flow conditions
This value is critical for determining:
Water supply adequacy
System performance under demand
Step 6: Measure Flow Rate
Flow rate can be measured using:
Pitot gauge (most common)
Flow meters
Diffuser devices with known discharge coefficients
NFPA 291 provides formulas and tables for calculating flow based on:
Pitot pressure
Outlet size
Coefficient of discharge
Flow is typically expressed in:
GPM (gallons per minute)
Or L/min (Canada)
Step 7: Calculate Available Fire Flow
Using NFPA 291 calculations, the tester determines:
Available fire flow at a residual pressure of 20 psi (138 kPa), unless otherwise specified
This calculated fire flow is used by:
Fire protection engineers
Sprinkler designers
Fire departments
Accurate calculations are essential for system design approval.
Step 8: Close Hydrants and Restore System
After testing:
Close hydrants slowly to prevent water hammer
Remove gauges and equipment
Verify that hydrants are fully closed
Check for leaks or drainage issues
Step 9: Document and Report Results
A compliant hydrant flow test report includes:
Test date and location
Hydrant identification numbers
Static pressure
Residual pressure
Flow rate
Calculated available fire flow
Notes on deficiencies or abnormalities
In Ontario, these reports are often required for:
Building permits
Fire protection system verification
Insurance documentation
Fire department records
Hydrant Color Coding Under NFPA 291
NFPA 291 also establishes hydrant marking based on flow capacity:
| Color | Flow Capacity |
|---|---|
| Blue | 1,500+ GPM |
| Green | 1,000–1,499 GPM |
| Orange | 500–999 GPM |
| Red | Below 500 GPM |
In Ontario, hydrant color coding is commonly used to assist firefighters during emergencies.
Common Mistakes During Hydrant Flow Testing
Improper testing can produce misleading results. Common errors include:
Using only one hydrant for static and residual pressure
Diffuser devices with unknown discharge coefficients
Failing to measure residual pressure
Not fully opening the test hydrant
Inaccurate pitot placement
Incomplete documentation
Following NFPA 291 prevents these issues.
NFPA 291 vs Field Reality in Ontario
While NFPA 291 provides the technical procedure, Ontario testing must also consider:
Municipal bylaws
Traffic and environmental controls
Seasonal conditions (freezing risk)
Public safety and property protection
Professional testing balances standard compliance with local conditions.
How NFPA 291 Supports Ontario Fire Code Compliance
The Ontario Fire Code requires:
Fire protection systems are to be maintained and reliable
Testing to follow recognized standards
NFPA 291 provides the defensible methodology used to demonstrate compliance and due diligence.
Who Should Perform NFPA 291 Hydrant Flow Tests?
Hydrant flow testing should be performed by:
Trained fire protection professionals
Qualified contractors with proper equipment
Authorized personnel approved by the municipality (for public hydrants)
Improper testing can damage infrastructure or produce unusable data.
Best Practice Summary for Ontario
To ensure accurate and compliant hydrant flow testing:
Follow NFPA 291 procedures exactly
Coordinate with authorities when required
Use calibrated equipment
Document results thoroughly
Repeat testing every 5 years or as required
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