Chapter VII
Fixtures and Appliances
Red Seal Practice study guide with diagrams.
Plumbing Fixtures and Accessories
Chapter Introduction
This chapter covers all the knowledge required for the Red Seal exam concerning the installation, connection, verification, and troubleshooting of plumbing fixtures and their accessories. You must master not only the operating principles but also the regulatory requirements of the National Plumbing Code of Canada (NPC) and relevant CSA standards. This chapter is structured to follow the exam logic: first classifications and definitions, then installation requirements, load calculations, and finally typical traps.
Classification of Plumbing Fixtures
Regulatory Definition
According to the NPC, a plumbing fixture is any receptacle or fixed device that receives potable water or wastewater and is connected to a drainage system. This definition excludes water treatment equipment and appliances not connected to drainage (e.g., portable dishwashers).
Main Categories
| Category | Examples | Installation Particularity |
|---|---|---|
| Gravity-drainage fixtures | Sinks, bathtubs, showers, lavatories | Minimum slope of 2% (¼ in/ft) on the drain |
| Pressure-flush fixtures | Pressure-assisted toilets, valve-type urinals | Require supply pressure ≥ 345 kPa (50 psi) |
| Fixtures with integral pump | Sump stations, garbage disposers | Electrical connection required, dedicated venting |
| Specialized fixtures | Fountains, therapeutic baths, laboratory sinks | Specific CSA standards (CSA B45.0, CSA B45.5) |
Applicable Manufacturing Standards
Every installed fixture must be certified to a recognized CSA standard:
CSA B45.0: General requirements for ceramic plumbing fixtures.
CSA B45.1: Ceramic sinks and basins.
CSA B45.2: Enamelled steel bathtubs.
CSA B45.5: Toilets and urinals (flush performance, water volume ≤ 6.0 L).
CSA B45.10: Fibreglass-reinforced plastic fixtures.
ASME A112.19.2: Vitreous china fixtures (CSA cross-reference).
> Exam Trap: A fixture without a CSA certification mark or equivalent (e.g., UPC, IAPMO) cannot be installed, even if it is functional. The NPC requires independent certification.
General Installation Requirements
Water Supply Connection
Each fixture must be connected to a potable water supply with an accessible individual shut-off valve. Notable exceptions:
Bathtubs (shut-off valve required within 1.5 m).
Showers with thermostatic mixing valves (shut-off valve required).
Toilets (shut-off valve mandatory, typically a ⅜ in angle valve).
The maximum allowable static pressure at the faucet is 550 kPa (80 psi). Beyond this, a pressure-reducing valve (regulator) must be installed on the main supply line.
Drainage Connection
Each fixture must have an individual or shared trap according to the following rules:
One trap may serve two adjacent fixtures if the horizontal distance between the two drains is ≤ 750 mm (30 in).
One trap may not serve more than two fixtures.
Bathtubs and showers must have a 2 in (50 mm) minimum trap.
Kitchen sinks must have a 1½ in (38 mm) minimum trap, but 2 in is recommended if a garbage disposer is installed.
Fixture Venting
Each fixture must be vented in accordance with the NPC, Chapter 2, Part 2.5. Essential rules:
The maximum distance between the trap and the vent (known as the "venting distance") is calculated according to Table 2.5.6.2. of the NPC. For a 1¼ in drain, the maximum distance is 1.2 m; for 1½ in, 1.5 m; for 2 in, 1.8 m; for 3 in, 2.7 m.
Wet venting is permitted for toilets and lavatories in a bathroom, provided the vent drain has a minimum diameter of 2 in.
Relief vents (circuit venting) are required for fixture batteries (≥ 2 fixtures) in commercial installations.
Specific Fixtures: Detailed Requirements
Toilets (WC)
Types and Flush Volumes
| Type | Flush Volume | Required Pressure | Typical Use |
|---|---|---|---|
| Gravity (tank) | 4.8 – 6.0 L | 345 kPa min. | Residential |
| Pressure-assisted | 3.5 – 4.8 L | 345 – 550 kPa | Commercial, institutional |
| Vacuum-assisted | 1.0 – 1.5 L | 550 kPa min. | Airports, hospitals |
| Composting | 0 L (waterless) | N/A | Cottages, remote sites |
Installation Rules
The clearance in front of the toilet must be ≥ 600 mm (24 in).
The side clearance between the centre of the toilet and a wall or another fixture must be ≥ 375 mm (15 in).
The flange must be secured to the finished floor, with the top of the flange level with the finish.
The wax seal or alternative (rubber ring) must be centred and compressed evenly.
The bowl must be secured with brass or stainless steel bolts, never carbon steel (corrosion).
Frequent Exam Errors
Confusing the 375 mm distance (centre to wall) with the 300 mm distance (centre to wall for a lavatory).
Forgetting that the toilet must be the last fixture connected to the drain (closest to the drainage stack) in a bathroom, to prevent backflow.
Bathtubs and Showers
Bathtubs
The bathtub must be installed with a support if the span exceeds 1.5 m without support.
The integral overflow must be connected to the trap, never directly to the drain.
The bathtub trap must be 2 in (50 mm) minimum, with a 2% slope.
The tub-shower valve assembly must comply with CSA B125.1 (faucets) and ASME A112.18.1.
Showers
The shower base must have a 2 in (50 mm) minimum drain.
The waterproof membrane (liner) must extend at least 50 mm (2 in) above the threshold of the base.
A thermostatic mixing valve is mandatory for showers in healthcare facilities (hospitals, residences) according to the NPC, Article 2.6.3.2. The maximum outlet temperature is 49 °C (120 °F).
The shower floor slope (if a site-built receptor) must be 1:50 toward the drain.
> Exam Trap: A thermostatic mixing valve is not mandatory in a single-family private residence, but it is strongly recommended. Do not confuse it with a mechanical mixing valve (without thermostat) which does not maintain temperature.
Sinks and Lavatories
Kitchen Sinks
The drain must be 1½ in (38 mm) minimum; 2 in if a garbage disposer is installed.
The garbage disposer must be connected to the drain with a 2 in trap and dedicated venting if the distance to the main trap exceeds 1.5 m.
The dishwasher must be connected to the sink drain with a vacuum breaker (backflow preventer) conforming to CSA B64.2, installed above the countertop.
The sink faucet must have a spout with an air gap of at least 25 mm above the rim of the highest receptacle.
Lavatories (Bathroom)
1¼ in (32 mm) minimum drain.
The overflow of the lavatory is integral and must be free of any obstruction.
Sensor faucets (infrared) must conform to CSA B125.1 and have a Class 2 electrical supply (24 V AC or 12 V DC).
Mounting height of the lavatory: top edge between 800 and 850 mm from the finished floor (residential use).
Urinals
1½ in (38 mm) minimum drain, with integral or individual trap.
The flush must be limited to 1.9 L per use (flush-type urinal) or 0 L (waterless urinal).
Waterless urinals use a sealant liquid cartridge; the cartridge must be replaced according to the manufacturer's instructions (typically every 5,000 to 7,000 uses).
The venting of the urinal must be individual or shared with another urinal in the same room.
Therapeutic Baths and Spas
Electrical connection in accordance with the Canadian Electrical Code, Part I (CE Code) (Rule 8-200 for branch circuits).
The drain must be 2 in minimum, with a trap with permanent seal.
The circulation pump must be accessible for maintenance.
A backflow preventer of type RP (reduced pressure) is required on the water supply if the bath is equipped with a recirculation pump.
Load Calculations and Sizing
Fixture Units
The NPC uses the fixture unit (F.U.) system for sizing pipes. Each fixture has a fixed value:
| Fixture | Fixture Units (Supply) | Fixture Units (Drainage) |
|---|---|---|
| Toilet (6 L tank) | 2.5 | 3 |
| Toilet (pressure-assisted) | 3.0 | 3 |
| Lavatory (bathroom) | 1.0 | 1 |
| Kitchen sink | 1.5 | 2 |
| Bathtub | 2.0 | 2 |
| Shower | 2.0 | 2 |
| Urinal (flush) | 2.0 | 2 |
| Waterless urinal | 0.5 | 1 |
| Dishwasher | 1.5 | 2 |
| Garbage disposer | 1.0 | 1 |
| Laundry (sink + machine) | 2.0 | 3 |
Sizing Supply Pipes
The sizing method uses Table 2.6.1.2. of the NPC. Steps:
92.Calculate the total fixture units (supply) for all fixtures.
93.Determine the probable flow rate (L/min) using the probability table (simplified Hunter's curve).
94.Choose the pipe diameter based on velocity (≤ 2.4 m/s) and pressure loss (≤ 1 m/100 m).
Calculation Example:
Single-family house: 2 full bathrooms (2 × [WC + lavatory + shower]) + kitchen (sink + dishwasher) + laundry.
Total F.U. = (2.5 + 1 + 2) × 2 + (1.5 + 1.5) + (2 + 1) = 11 + 3 + 3 = 17 F.U.
Probable flow ≈ 30 L/min (according to table).
Minimum main supply pipe diameter: ¾ in (19 mm) copper type M or ¾ in PEX.
Sizing Drains
Table 2.5.7.1. of the NPC gives minimum diameters:
| Drain Diameter (in) | Maximum Fixture Units | Minimum Slope |
|---|---|---|
| 1¼ | 1 | 2% |
| 1½ | 3 | 2% |
| 2 | 6 | 2% |
| 3 | 20 | 1% |
| 4 | 160 | 1% |
> Exam Trap: A 2 in drain can support 6 F.U. at a 2% slope, but only 4 F.U. if the slope is reduced to 1%. The slope affects hydraulic capacity.
Safety Rules and Backflow Protection
Backflow Preventers
According to the NPC, Article 2.6.3.1., any cross-connection between potable water and a source of contamination must be protected. Devices are classified by risk level:
| Device Type | CSA Standard | Typical Use | Protection Level |
|---|---|---|---|
| Air gap | — | Sink faucets, dishwashers | High (air space ≥ 25 mm) |
| Double check valve assembly (DCVA) | CSA B64.5 | Residential irrigation | Low to medium |
| Reduced pressure principle device (RP) | CSA B64.4 | Boiler supply, therapeutic baths | Very high |
| Double check valve (DC) | CSA B64.5 | Pollution protection (non-toxic) | Medium |
Specific Rules
A vacuum breaker must be installed on any exterior faucet (hose bib) with threads (CSA B64.2 standard).
Toilets with tanks have an integral backflow preventer (flush valve), but a pressure-assisted toilet requires an RP if the supply pressure exceeds 550 kPa.
Dishwashers must have a vacuum breaker or an air gap, never a simple check valve.
Installation and Commissioning Procedures
Toilet Installation (Typical Procedure)
116.Check the alignment of the flange: it must be level, at 90° to the finished wall.
117.Install the wax seal on the flange (or the rubber ring).
118.Set the toilet, pressing evenly to compress the seal.
119.Tighten the bolts alternately (cross-pattern), without over-tightening (torque of 5–7 N·m).
120.Connect the water supply with a stainless steel braided flexible hose (not rigid copper).
121.Open the shut-off valve, check for leaks at the seal and the tank.
122.Test the flush: the volume must be ≤ 6.0 L and complete emptying in ≤ 10 seconds.
Shower Commissioning
124.Purge air from the pipes (open the valve in hot position then cold).
125.Check the outlet temperature with a thermometer: ≤ 49 °C for thermostatic mixing valves.
126.Test the pressure: between 345 and 550 kPa.
127.Check the base for watertightness (fill with water to the threshold, observe for 10 minutes).
128.Check the flow rate: ≥ 9.5 L/min for a standard shower, ≥ 7.6 L/min for a low-flow shower.
Traps to Avoid
131.Confusing fixture units: Supply and drainage use different values for the same fixture. Example: a toilet = 2.5 F.U. (supply) but 3 F.U. (drainage).
132.Forgetting venting: A fixture without adequate venting causes siphoning of the water seal. The trap-to-vent distance is often miscalculated.
133.Neglecting the slope: A 1% slope (⅛ in/ft) is acceptable for a 3 in drain, but never for a 1½ in drain (minimum 2%).
134.Installing a vacuum breaker too low: The vacuum breaker must be above the highest overflow point of the fixture. If it is lower, it does not protect.
135.Using carbon steel bolts to secure a toilet: they rust and break.
136.Forgetting the individual shut-off valve: Every fixture must have one, except for very limited exceptions (e.g., bathtub with difficult access).
137.Confusing standards: CSA B45.5 is for toilets, not bathtubs. Always read the label.
138.Not checking pressure: A pressure > 550 kPa without a pressure-reducing valve is a violation of the NPC.
139.Connecting the bathtub overflow to the drain: The overflow must go to the trap, never directly to the main drain.
140.Installing a dishwasher without a vacuum breaker: Backflow of dirty water into the dishwasher is a major health risk.
Summary
Plumbing fixtures are classified by type (gravity, pressure, pump) and must be certified to CSA B45.x standards.
Each fixture requires an individual shut-off valve, a trap (except for exceptions), and venting in accordance with the NPC.
Venting distances and drain diameters are governed by specific tables (NPC 2.5.6.2 and 2.5.7.1).
Fixture units (F.U.) are the basis for sizing: supply (Table 2.6.1.2) and drainage (Table 2.5.7.1).
Backflow protection is mandatory: air gap, check valve, or RP depending on the risk level.
Thermostatic mixing valves are mandatory in healthcare facilities (temperature ≤ 49 °C).
Toilet flush volumes are limited to 6.0 L (residential) and 1.9 L (urinals).
Commissioning procedures include air purging, pressure tests, and temperature verification.
Self-Assessment Questions (Exam-Type)
153.What is the maximum distance between the trap of a lavatory (1¼ in drain) and its vent?
a) 1.2 m
b) 1.5 m
c) 1.8 m
d) 2.7 m
(Answer: a)
159.A garbage disposer is installed on a kitchen sink. What is the minimum drain diameter?
a) 1¼ in
b) 1½ in
c) 2 in
d) 3 in
(Answer: c)
165.What is the maximum allowable pressure at a faucet without a pressure-reducing valve?
a) 345 kPa
b) 450 kPa
c) 550 kPa
d) 700 kPa
(Answer: c)
171.How many fixture units does a waterless urinal have for drainage?
a) 0.5
b) 1
c) 2
d) 3
(Answer: b)
177.Which backflow prevention device is required for a therapeutic bath with a recirculation pump?
a) Air gap
b) Single check valve
c) Reduced pressure principle device (RP)
d) Double check valve
(Answer: c)
Key Normative References
National Plumbing Code of Canada (NPC) 2020: Chapters 2 (installations), 3 (materials), 4 (wastewater).
CSA B45.0 / B45.1 / B45.2 / B45.5 / B45.10: fixture standards.
CSA B125.1: faucets and accessories.
CSA B64.2 / B64.4 / B64.5: backflow prevention devices.
Canadian Electrical Code, Part I (CE Code): Rule 8-200 (branch circuits for fixed appliances).
> Final Advice: On the exam, read each question twice. The most common traps involve fixture units, minimum diameters, and venting distances. Memorize the NPC tables, not isolated values. Good luck with your preparation!
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