Testing, Commissioning, and Troubleshooting
This chapter covers all the testing, commissioning, and troubleshooting procedures that every journeyperson plumber must master for the Red Seal exam. These skills represent a significant portion of daily tasks and are systematically evaluated on the exam, both theoretically and practically.
Learning Objectives
By the end of this chapter, you will be able to:
Plan and execute static and dynamic pressure tests on potable water supply systems
Perform leak tests on drainage, waste, and venting (DWV) systems
Commission sanitary fixtures and heating systems
Diagnose common faults using appropriate measuring tools
Interpret test results according to the requirements of the National Plumbing Code (NPC) and the Canadian Electrical Code, Part I
1. Fundamental Principles of Testing
1.1 Why Test?
Testing serves to verify three essential qualities of an installation:
14.Leak-tightness — absence of leaks in pressure and gravity systems
15.Functionality — fixtures and systems operate according to their specifications
16.Safety — the installation presents no danger to occupants (sewer backflow, cross-contamination, electrical hazards)
1.2 Types of Tests
| Type of Test | System Targeted | Fluid Used | Typical Pressure |
|---|
| Static pressure | Water supply | Water | 1.0 to 1.5 times the service pressure (min. 700 kPa) |
| Air pressure | DWV | Compressed air | 35 kPa (5 psi) |
| Water pressure | DWV | Water | Up to overflow level |
| Smoke | DWV | Artificial smoke | Low pressure |
| Dye (colourant) | DWV | Water + dye | Gravity |
| Pressure drop | Gas (if applicable) | Air or inert gas | Per CSA B149.1 |
1.3 Service Pressure vs. Test Pressure
Service pressure is the normal operating pressure of the system. Test pressure must always be higher than the service pressure to reveal potential defects. The NPC requires that tests be performed at a pressure of at least 700 kPa (100 psi) for water supply systems, or at 1.5 times the service pressure if it exceeds 700 kPa.
> Key NPC Rule: No water supply system may be covered or concealed before having successfully passed the required tests.
2. Testing Water Supply Systems
2.1 Static Pressure Test
Principle: Fill the system with water, purge the air, then apply test pressure for a specified duration. The pressure must not drop by more than 35 kPa (5 psi) in 30 minutes.
Detailed Procedure:
27.Connect the test pump (hand pump or electric) to the lowest point of the system
28.Slowly fill the system from the low point to allow air to escape through the high points
29.Purge all air completely — the presence of air falsifies readings (air compresses, water does not)
30.Close all faucets and valves
31.Raise the pressure to the test value (700 kPa minimum)
32.Maintain the pressure for 30 minutes
33.Observe any pressure drop — a drop of more than 35 kPa indicates a leak
Points of Caution:
Threaded fittings and soldered joints are the most common leak points
A poorly calibrated pressure gauge gives erroneous readings — check its zero before testing
Thermal expansion can raise the pressure beyond the test value — monitor during the test
2.2 Dynamic Pressure Test
The dynamic test verifies the system's behaviour under real flow conditions. You measure:
Standing pressure (static)
Flowing pressure (dynamic) — it must remain above 150 kPa (22 psi) at points of use
Flow rate at fixtures — verify it matches manufacturer specifications
Head Loss Calculation: The head loss ΔP in piping depends on the flow rate Q, inside diameter d, length L, and friction coefficient f:
ΔP = f × (L/d) × (ρv²/2)
Where ρ is the fluid density and v is the flow velocity. For the exam, remember that:
Head loss increases with the square of the velocity
A smaller diameter significantly increases head loss
90° elbows and sudden reductions create significant local losses
2.3 Hot Water Recirculation Test
For hot water recirculation systems:
51.Verify the operation of the recirculation pump
52.Measure the temperature at different points in the system — the difference must not exceed 5 °C between the starting point and the farthest point
53.Verify the operation of the check valve (prevents backflow into the cold water line)
54.Test the thermostat and control timers
3. Testing Drainage, Waste, and Venting (DWV) Systems
3.1 Water Test (Hydrostatic Test)
Principle: Fill the drainage system with water up to the overflow of the highest point, or to a height of at least 3 m (10 ft) in the highest vent stack.
Procedure:
60.Temporarily plug all low openings (outlets to the sewer, fixture connections)
61.Fill the system with water from the top
62.Leave the water in place for 15 minutes minimum
63.Visually inspect all accessible joints and connections
64.No leaks are tolerated
Advantages and Limitations:
Water is easier to detect visually than air
The water test does not test gas-tightness — a joint can allow gas to pass without allowing water to pass
The weight of the water can damage poorly supported pipes
3.2 Air Test
Principle: Introduce compressed air into the DWV system and verify pressure stability.
Procedure:
72.Plug all openings with airtight test plugs
73.Introduce air at a pressure of 35 kPa (5 psi) for pipes with a diameter ≤ 100 mm (4 in)
74.For larger diameters, the test pressure is 21 kPa (3 psi)
75.Maintain the pressure for 15 minutes
76.A pressure drop indicates a leak — locate it with a soapy solution (bubbles)
Caution: Never exceed 105 kPa (15 psi) for air tests on DWV systems — risk of joint blowout and serious injury.
3.3 Smoke Test
Principle: Introduce artificial smoke (usually paraffin smoke or non-toxic coloured smoke) into the system to detect leaks visually.
Procedure:
81.Plug all openings except one
82.Introduce the smoke using a generator
83.Observe the appearance of smoke at defective joints, cracks, or connections
84.Mark leak points for repair
Limitations: Smoke does not travel well through wet or partially obstructed systems. It is not suitable for systems containing water-filled traps.
3.4 Dye Test
Used to verify the tightness of connection joints and the absence of leaks in buried or inaccessible systems:
88.Pour a dye (fluorescein) into the system
89.Wait the prescribed time (usually 30 minutes)
90.Inspect suspect areas with a UV lamp if the dye is fluorescent
91.The presence of dye indicates a leak
3.5 Testing Traps and Vents
Verify that each fixture has an adequate water seal (50 mm to 75 mm depending on the fixture)
Test the hydraulic seal by pouring water into the fixture and observing the level in the trap
Verify that vents are open and unobstructed — a simple test consists of running water into a fixture and observing the drainage speed; slow drainage with gurgling indicates insufficient venting
4. System Commissioning
4.1 Commissioning a Water Supply System
Complete Procedure:
100.Flushing: Open all faucets to purge air and remove solder residue, filings, and other debris
101.Disinfection: According to NPC requirements, the system must be disinfected before commissioning — typically by chlorination (chlorine solution at 50 mg/L for 24 hours, or per local specifications)
102.Pressure verification: Measure static and dynamic pressure at points of use
103.Temperature verification: Measure the hot water temperature at the farthest faucet — it must reach at least 50 °C (per codes) within a reasonable time
104.Leak check: Visually inspect all accessible connections after pressurization
4.2 Commissioning a Water Heater
Procedure:
107.Verify that the tank is completely filled with water before energizing or lighting the burner
108.Open a hot water faucet to purge air from the tank
109.Verify the operation of the temperature and pressure relief valve (T&P valve) — it must be manually operated to verify its function (caution: hot water)
110.Set the thermostat to the desired temperature (usually 60 °C to prevent legionella, with mixing valves at points of use)
111.Check for leaks at connections and at the safety group
4.3 Commissioning Sanitary Fixtures
| Fixture | Essential Checks |
|---|
| Toilet | Stability, base seal, flush mechanism operation, no tank leaks |
| Lavatory | Connection tightness, water flow and temperature, proper drainage, overflow function |
| Bathtub | Tightness, proper drainage, overflow and drain function |
| Shower | Pressure and temperature, receptor tightness, showerhead function |
| Kitchen sink | Tightness, flow rate, disposer operation (if installed), proper drainage |
| Dishwasher | Connection to DWV system with **backflow prevention loop** (air gap), tightness, operating cycle |
4.4 Commissioning Backflow Prevention Systems
Backflow prevention devices must be tested after installation and periodically:
116.Check valve: Verify tightness in the reverse flow direction
117.Reduced pressure zone (RPZ) assembly: Test both check valves and the differential relief valve
118.Air gap: Verify the vertical distance between the discharge point and the overflow level of the receptacle — this distance must be at least 2 times the pipe diameter (minimum 25 mm)
5. Troubleshooting — Methodology and Tools
5.1 Systematic Troubleshooting Approach
The five-step method:
123.Identify the symptom — gather information from the occupant (when, how, since when)
124.Analyze possible causes — establish a list of probable causes, from simplest to most complex
125.Isolate the cause — perform targeted tests to eliminate hypotheses
126.Correct the problem — perform the appropriate repair
127.Verify the solution — test the system to confirm the problem is resolved and no new problems have appeared
5.2 Essential Diagnostic Tools
| Tool | Use |
|---|
| Pressure gauge | Measuring static and dynamic pressure |
| Differential pressure gauge | Measuring head loss across a filter or valve |
| Infrared thermometer | Remote temperature measurement, detecting thermal leaks |
| Inspection camera | Visual inspection of piping (DWV, ducts) |
| Acoustic leak detector | Locating leaks by sound amplification |
| Continuity tester / multimeter | Checking electrical circuits (water heaters, pumps) |
| Ultrasonic thickness gauge | Measuring residual thickness of corroded pipes |
| Fluorescent dye + UV lamp | Detecting leaks in pressure systems |
5.3 Common Problems and Solutions
5.3.1 Insufficient Water Pressure
Possible Causes:
Partially closed valve — check all shut-off valves
Clogged filter or aerator — disassemble and clean
Undersized piping — verify sizing calculations
Corrosion or scaling — reduces the effective inside diameter
Leak in the system — a significant leak reduces available pressure
Defective booster pump (if installed) — verify operation
Diagnosis: Measure the pressure at the meter (static pressure), then at points of use. If the pressure is good at the meter but low at the faucets, the problem is in the internal system. If it is low at the meter, the problem is upstream (municipal supply or well).
5.3.2 Water Hammer
Cause: Sudden change in flow velocity when a valve or faucet closes quickly. The kinetic energy of the water is transformed into a pressure wave.
Approximate Surge Pressure Calculation: ΔP = ρ × c × Δv
Where c is the wave velocity (approximately 1200 m/s in water in steel pipe) and Δv is the velocity change. For a velocity change of 1 m/s, the surge pressure is approximately 1200 kPa — more than 12 times atmospheric pressure!
Solutions:
Install water hammer arrestors at fixtures with quick-closing valves (washing machines, dishwashers)
Verify that air chambers (closed vertical pipes) are not filled with water
Reduce the supply pressure if it is excessive (> 550 kPa)
Close faucets gradually (for manual valves)
5.3.3 Slow Drainage in DWV Systems
Possible Causes:
Partial blockage — grease, hair, debris
Insufficient slope — the minimum slope is 1/4 in per foot (20 mm/m) for pipes 3 in and smaller
Inadequate venting — traps are siphoned, creating air locks
Sagged pipe — creating pockets of standing water
Diagnosis: Observe the flow in one fixture while other fixtures are being used. If drainage slows when a toilet is flushed, the problem is likely inadequate venting.
5.3.4 Noises in Piping
| Type of Noise | Probable Cause | Solution |
|---|
| Banging | Thermal expansion | Pipe supports with elastic clamps |
| Whistling | Excessive pressure or partially closed valve | Reduce pressure, fully open the valve |
| Gurgling | Inadequate venting | Correct the venting |
| Squeaking | Friction on supports | Lubricate or reposition supports |
| Clattering on closure | Water hammer | Install water hammer arrestors |
5.3.5 Water Leaks
Locating Leaks:
160.Visible leak: Inspect visually — most leaks are found at connections, joints, and points of connection
161.Hidden leak: Use an acoustic detector or thermal camera
162.Leak in a slab: Measure pressure, close sectional valves to isolate the area, use an acoustic correlation leak detector
Repair: Shut off the supply, drain the affected section, repair or replace the defective section, then perform a pressure test to confirm tightness.
6. Regulatory Requirements and Standards
6.1 National Plumbing Code (NPC)
The NPC is the primary reference for testing and commissioning. Key articles concern:
Mandatory tests: All water supply and drainage systems must be tested before being covered or concealed
Test pressure: 700 kPa minimum for water supply
Test duration: 30 minutes for water supply, 15 minutes for DWV
Disinfection: The water supply system must be disinfected after installation
6.2 Canadian Electrical Code, Part I
This code applies to electrical installations in buildings, including electrical plumbing equipment (water heaters, pumps, boosters). Relevant points:
Grounding: Metallic piping must be grounded per Rule 10-400
Bonding: Metallic piping must be bonded together (Rule 10-402)
Circuit protection: Circuits supplying plumbing equipment must be protected according to their amperage (Rule 14-100)
> Important for the exam: The plumber does not perform electrical work but must be able to recognize hazards and coordinate their work with the electrician.
6.3 CSA B149.1 — Natural Gas and Propane Code
For gas installations serving water heaters and hot water generators:
Leak test: The gas system must be tested with air or inert gas at a pressure of 35 kPa (5 psi) for 15 minutes minimum
Purging: The system must be purged before commissioning to remove air
Flame verification: Combustion must be verified (stable blue flame, no yellow)
7. Useful Calculations and Conversions
7.1 Pressure Conversions
| Unit | Equivalent |
|---|
| 1 kPa | 0.145 psi |
| 1 psi | 6.895 kPa |
| 1 bar | 100 kPa |
| 1 atmosphere | 101.325 kPa |
| 1 m of water column | 9.81 kPa |
7.2 Hydrostatic Pressure
P = ρ × g × h
Where ρ = 1000 kg/m³ for water, g = 9.81 m/s², h = height in metres.
For each metre of water height, the pressure increases by 9.81 kPa. A 10 m water column produces approximately 98 kPa (14 psi).
7.3 Flow Rate and Velocity
Q = A × v
Where Q is the flow rate (m³/s), A is the pipe cross-section (m²), and v is the velocity (m/s).
Recommended Velocities:
Water supply: 1.5 to 3 m/s (maximum 4 m/s to avoid noise and erosion)
DWV: 0.6 to 3 m/s (minimum self-cleaning velocity of 0.6 m/s)
7.4 Head Loss in Piping
For the exam, remember the following orders of magnitude (Type L copper piping):
| Diameter (in) | Flow Rate (L/min) | Head Loss (kPa/m) |
|---|
| 1/2 | 8 | 2.5 |
| 3/4 | 15 | 2.0 |
| 1 | 25 | 1.5 |
| 1-1/4 | 40 | 1.2 |
| 1-1/2 | 60 | 1.0 |
These values are approximate and depend on roughness, temperature, and the number of fittings.
8. Safety During Testing
8.1 Risks Associated with Testing
Excessive pressure: An air test on a DWV system can eject plugs with force — always use test plugs designed for this purpose
Hot water: During tests on hot water systems, water can reach 80 °C — wear insulating gloves
Chlorine: Disinfection uses chlorine solutions — wear respiratory and eye protection
Electricity: Electric water heaters and pumps present a shock hazard — disconnect the power before any intervention
Gas: Gas testing requires adequate ventilation and no smoking
8.2 Personal Protective Equipment (PPE)
Safety glasses (mandatory during pressure tests)
Work gloves (mechanical and thermal protection)
Steel-toe safety boots
Hearing protection if using noisy tools
Respirator mask when using chemical products
9. Documentation and Test Reports
9.1 Contents of a Test Report
A complete test report must include:
219.Date and time of the test
220.Project identification and location
221.Type of test performed (pressure, leak-tightness, smoke, etc.)
222.Test pressure applied and duration
223.Results (passed/failed)
224.Observations (leaks detected, corrections made)
225.Name and signature of the responsible journeyperson plumber
226.Licence or certification number
9.2 Importance of Documentation
Documentation proves compliance with codes and standards
It serves as a reference for future inspections
It protects the plumber in case of disputes
It is required by authorities for issuing occupancy certificates
10. Pitfalls to Avoid
Here are the most frequent errors made by Red Seal exam candidates on this subject:
235.Confusing service pressure and test pressure — Test pressure is always higher than service pressure (700 kPa minimum for water)
236.Forgetting to purge air before a pressure test — Compressed air falsifies readings and can give a false positive result
237.Using air for pressure tests on water systems — Air testing is reserved for DWV systems; for water, use water
238.Neglecting disinfection — The NPC requires disinfection of the potable water system after installation
239.Ignoring venting requirements — A poorly vented DWV system fails functional tests even if leak-tightness is good
240.Not checking the T&P valve — This is a systematic check point when commissioning a water heater
241.Confusing pressure units — Know how to quickly convert kPa to psi (1 psi ≈ 7 kPa)
242.Forgetting that tests must be performed before concealment — Once pipes are covered, testing becomes much more difficult
243.Not documenting tests — The absence of a written report can result in rejection of the installation
244.Underestimating water hammer — Surge pressure calculations show that velocity changes create enormous pressures
11. Exam Tips
Memorize key values: 700 kPa (water test pressure), 35 kPa (DWV air test), 30 minutes (water test duration), 15 minutes (DWV test duration)
Understand the physical principles: The pressure-height relationship (9.81 kPa/m), the flow-velocity-area relationship
Know how to identify tools: You will be shown photos of tools — recognize the pressure gauge, test pump, test plug, and leak detector
Review the standards: NPC, CSA B149.1, Canadian Electrical Code, Part I — know their respective areas of application
Practice conversions: kPa ↔ psi, metres ↔ feet, litres ↔ gallons
Summary
Testing, commissioning, and troubleshooting constitute an essential part of the plumber's trade. The essential points to remember:
255.Water supply testing: Test pressure of 700 kPa minimum, duration of 30 minutes, maximum drop of 35 kPa
256.DWV testing: Water test (fill to overflow) or air test (35 kPa for ≤ 100 mm), duration of 15 minutes
257.Disinfection: Mandatory before commissioning the potable water system
258.Commissioning: Systematic verification of all fixtures, including the T&P valve and backflow prevention devices
259.Troubleshooting: Methodical five-step approach, use of appropriate diagnostic tools
260.Safety: Mandatory PPE, precautions during pressure tests and chlorine handling
261.Documentation: Complete and signed test reports for each installation
262.Standards: Compliance with the NPC, CSA B149.1, and the Canadian Electrical Code, Part I
Mastery of these skills distinguishes the qualified journeyperson plumber and ensures the safety and reliability of sanitary installations. For the Red Seal exam, focus on numerical values, standard procedures, and underlying physical principles — these are the most frequently evaluated elements.
