Chapter VI
Plumbing, Water Systems, and Waste Management (CSA B45 / National Plumbing Code)
Red Seal Practice study guide with diagrams.
Plumbing, Water Systems, and Wastewater Management (CSA B45 / National Plumbing Code)
This chapter covers all the knowledge required for the Red Seal exam concerning potable water systems, domestic hot water, and wastewater management in recreational vehicles (RVs). You must master the CSA B45 standards (plumbing fixtures) and the requirements of the National Plumbing Code of Canada 2020 (NPC), applied to the mobile context of RVs. The focus is on safety, prevention of cross-contamination, and regulatory compliance.
1. Regulatory Framework and Essential Definitions
1.1 Standards Applicable to RVs
RVs are subject to specific standards that complement the NPC. The main references are:
CSA B45: Standard for plumbing fixtures and fittings (toilets, lavatories, sinks, bathtubs). It defines performance, durability, and finish requirements.
CSA Z240: Series of standards for recreational vehicles (RV series). Part CSA Z240.2 specifically addresses construction requirements, including plumbing systems.
National Plumbing Code of Canada (NPC): Applies to the installation, extension, alteration, and repair of plumbing systems. For RVs, the general principles of the NPC are applied, adapted to the mobile context.
1.2 Key Terminology (to Know for the Exam)
| Term | Definition (per the NPC) |
|---|---|
| **Potable water** | Water that meets the requirements of the authorities having jurisdiction and is safe for human consumption. |
| **Non-potable water** | Water not intended for human consumption (e.g., toilet flush water, rinse water). |
| **Cross-contamination** | Accidental mixing of potable water with non-potable water or a hazardous liquid. |
| **Backflow prevention device** | Mechanism preventing the return of water (backflow) into the potable water system. |
| **Drainage vent** | A pipe that allows air to enter the drainage system to prevent trap siphonage. |
| **Trap** | A device that retains a water seal to prevent the passage of sewer gas. |
| **Slope** | The incline of a drainage pipe, expressed as a percentage or in inches per foot. |
| **Pressure system** | A water supply system using a pump to pressurize the pipes. |
| **Gravity system** | A wastewater drainage system that relies on the natural slope of the pipes. |
1.3 Roles and Responsibilities of the Technician
As a Red Seal technician, you must:
Install, repair, and maintain RV plumbing systems.
Verify compliance with CSA B45 standards and the NPC.
Diagnose faults (leaks, blockages, pump failures).
Perform pressure and leak tests.
Advise clients on the safe use of systems (winterization, disinfection).
2. Potable Water Supply Systems
2.1 Components of a Typical System
A modern RV has two distinct water circuits: the potable water circuit (under pressure) and the grey/black water circuit (by gravity). The potable water circuit includes:
21.Fresh water tank: Typical capacity of 40 to 150 litres. Made of high-density polyethylene (HDPE) for strength and food-grade safety.
22.Water pump: A diaphragm or vane pump, typically 12 V DC. Typical flow rate: 10 to 20 L/min. It is self-priming and operates with a pressure switch.
23.City water connection: A pressurized inlet (40 to 60 psi) that bypasses the pump and tank.
24.Pressure regulator: Often integrated into the city water connection. It reduces municipal supply pressure (up to 80 psi) to a safe pressure for the RV (generally 40-50 psi).
25.Check valve: Mandatory on the pump outlet to prevent water from flowing back into the tank.
26.Low point drain: Allows the system to be completely drained for winterization.
27.Pipe network: Made of PEX (cross-linked polyethylene) or CPVC (chlorinated polyvinyl chloride). PEX is preferred for its flexibility and freeze resistance.
2.2 Pressure and Flow: Fundamental Principles
Pressure: Measured in pounds per square inch (psi) or kilopascals (kPa). 1 psi ≈ 6.895 kPa. The ideal pressure for an RV is 40 to 50 psi.
Flow rate: Measured in litres per minute (L/min). It depends on the pipe diameter and pressure.
Pressure loss: The friction of water in pipes reduces pressure. Elbows, fittings, and filters increase this loss.
Static vs. dynamic pressure: Static pressure is measured when water is not flowing. Dynamic pressure is measured when water is flowing. Dynamic pressure is always lower than static pressure.
Hydrostatic pressure calculation: P = ρ × g × h, where:
P = pressure in pascals (Pa)
ρ (rho) = density of water (≈ 1000 kg/m³)
g = gravitational acceleration (≈ 9.81 m/s²)
h = height of the water column in metres (m)
Example: For a water tank located 3 metres above a faucet, the hydrostatic pressure is: P = 1000 × 9.81 × 3 = 29,430 Pa ≈ 29.4 kPa ≈ 4.3 psi. This pressure is low, hence the need for a pump.
2.3 NPC Rules for Potable Water Protection
The NPC is very strict on preventing contamination. Here are the key rules (numbering per the 2020 NPC):
Rule 2.6.1.1.: No cross-connection between a potable water system and a non-potable water system is permitted, unless an approved backflow prevention device is installed.
Rule 2.6.2.1.: A backflow prevention device must be installed on all connections where a backflow risk exists (e.g., city water connection, pump outlet).
Rule 2.6.3.1.: Backflow prevention devices must be accessible for inspection and maintenance.
Types of backflow prevention devices:
Check valve: Simple, but does not protect against backflow caused by downstream pressure.
Backflow preventer: Two check valves with a reduced pressure zone between them. This is the safest device. It is mandatory on city water connections.
Air gap: A physical separation between the water outlet and the flood level rim of the receiving vessel. This is the most reliable protection.
2.4 Water Tank Disinfection Procedure
After servicing or before the season, the tank must be disinfected. Standard procedure:
50.Completely drain the tank.
51.Prepare a bleach solution (sodium hypochlorite) at 50 ppm (parts per million). For a 100 L tank, use approximately 10 mL of 5.25% bleach.
52.Fill the tank with the solution.
53.Open all faucets until the chlorine odour is detected.
54.Let it sit for at least 4 hours (or per manufacturer's instructions).
55.Drain the tank and rinse thoroughly with potable water.
Caution: Never use RV antifreeze in the potable water circuit. Use only products certified for food contact.
3. Hot Water Systems
3.1 Types of Water Heaters
Gas water heater (propane): Uses a propane burner. Efficient and fast (heats in 15-20 minutes). Requires venting to the outside.
Electric water heater: Uses an electric heating element (120 V or 240 V). Slower (30-45 minutes) but does not consume propane.
Combination water heater (gas/electric): Operates on gas when the RV is mobile or off-grid, and on electricity when plugged into a campsite.
Tankless water heater: Heats water on demand. More compact and energy-efficient, but limited flow rate.
3.2 Components and Safety
Temperature and Pressure Relief Valve (T&P valve): Mandatory on all water heaters. It opens if the temperature exceeds 99 °C (210 °F) or if the pressure exceeds 150 psi (1034 kPa). It must be connected to a drain pipe leading to the outside.
Sacrificial anode: A magnesium or aluminum rod that corrodes instead of the steel tank. It should be inspected annually and replaced if more than 60% consumed.
Bypass: A set of valves allows the water heater to be isolated from the water circuit for winterization (do not fill the water heater with antifreeze).
Safety relief valve: Do not confuse with the T&P valve. The safety relief valve protects only against overpressure, not overheating.
3.3 NPC Rules for Water Heaters
Rule 2.7.1.1.: Every water heater must be equipped with a temperature and pressure relief valve conforming to ASME A112.4.1 or CSA B125.3.
Rule 2.7.1.2.: The valve must be installed on the tank, at the top, with its discharge orifice directed downward.
Rule 2.7.1.3.: A discharge pipe must be connected to the valve and terminate at a maximum distance of 300 mm from the floor, without obstruction.
4. Drainage and Venting Systems
4.1 Principles of Gravity Drainage
The wastewater drainage system (grey water and black water) operates by gravity. Water flows from fixtures to a holding tank.
Grey water: Water from sinks, shower, and lavatory. Contains soap, hair, food residue.
Black water: Water from the toilet. Contains fecal matter and urine. Requires specific treatment (chemicals or composting).
4.2 Pipe Slopes and Diameters
The NPC requires minimum slopes to ensure adequate flow:
| Pipe Diameter (inches) | Minimum Slope (inches/foot) | Minimum Slope (%) |
|---|---|---|
| 1 ¼" | 1/4" per foot | 2.08% |
| 1 ½" | 1/4" per foot | 2.08% |
| 2" | 1/4" per foot | 2.08% |
| 3" | 1/8" per foot | 1.04% |
| 4" | 1/8" per foot | 1.04% |
Rule 2.4.5.1.: Drainage pipes must be installed with a uniform slope, without back slope or deformation.
Slope calculation: Slope (%) = (Vertical drop / Length) × 100. For a 2" pipe over a length of 10 feet, the vertical drop must be: 10 × 0.25 = 2.5 inches.
4.3 Traps and Venting
Trap: Each fixture must have a trap to prevent sewer gas from entering the living space. The water seal must be at least 50 mm (2 inches) and at most 100 mm (4 inches) (Rule 2.5.1.1.).
Venting: Traps must be vented to prevent siphonage. In an RV, venting is often provided by a vent pipe running to the roof or by an Air Admittance Valve (AAV) . An AAV is a mechanical device that opens to let air in when a negative pressure is created, but closes tightly to prevent gas from escaping.
Rule 2.5.4.1.: Each trap must be vented by a vent pipe or an AAV conforming to ASSE 1051.
4.4 Holding Tanks
Grey water tank: Typical capacity of 60 to 150 litres.
Black water tank: Typical capacity of 40 to 100 litres. It is equipped with a drain valve (usually a 3-inch T-handle valve).
Level sensor: An LED or gauge indicator that measures the fill level. Probe sensors are often fouled by deposits.
Black water treatment: Use of chemicals (formaldehyde, enzymes, bacteria) to break down solids and control odours. Enzyme-based products are preferred as they are less harmful to the environment.
4.5 Specific Rules for RVs (CSA Z240.2)
Tanks must be vented to the outside of the vehicle.
Drain valves must be accessible and located at a minimum height of 150 mm from the ground to allow hose connection.
Drainage pipes must be supported at maximum intervals of 1.2 metres to prevent sagging.
5. Propane Gas and Interaction with Plumbing
The gas water heater and stove use propane. The plumbing technician must know the basic safety rules, even though gas installation falls under CSA B149.1 (Natural Gas and Propane Installation Code).
Rule 5.16.1. (CSA B149.1): Gas appliances must be installed with adequate clearance from combustible materials.
Rule 5.20.1.: Gas piping must be supported and protected against mechanical damage.
Prohibition: A gas line must never pass through a water tank or an unvented crawl space.
Exam Point: The RV plumbing technician must know that the gas shut-off valve must be closed before any work on the water heater.
6. Winterization and De-winterization
6.1 Winterization Procedure
The goal is to protect the system from freezing. Standard procedure:
104.Drain the fresh water tank: Open the drain valve.
105.Drain the grey and black water tanks: Drain completely.
106.Bypass the water heater: Close the inlet and outlet valves on the water heater, then open the bypass valve.
107.Open all faucets: To let the water drain out.
108.Purge with compressed air: Use a compressor (30-40 psi) to blow residual water out of the pipes. Connect the compressor to the city water connection or a pump outlet.
109.Inject antifreeze: Use an antifreeze pump (or the RV's own pump) to circulate non-toxic antifreeze (propylene glycol) through all the lines. Open each faucet (hot and cold) until antifreeze comes out.
110.Pour antifreeze into the traps: To protect the P-traps.
111.Don't forget: The outdoor shower, the toilet, the drain valve.
6.2 De-winterization Procedure (Returning to Service)
113.Close the drain valves.
114.Fill the fresh water tank with clean water.
115.Open the faucets to purge air and flush out the antifreeze.
116.Fill the water heater: Close the bypass, open the water inlet, then open a hot water faucet to let the air escape.
117.Check for leaks: Inspect all connections.
118.Disinfect the fresh water tank (see section 2.4).
119.Test the pump and the pressure switch.
7. Mandatory Tests and Inspections
7.1 Water Supply System Leak Test
Air test: Pressurize the system to 50 psi (345 kPa) with compressed air. The pressure must not drop more than 2 psi in 15 minutes (Rule 2.8.1.1.).
Water test: Fill the system with water and pressurize it to the service pressure. Visually inspect all connections for leaks.
7.2 Drainage System Leak Test
Water test: Fill the drainage pipes with water to the overflow point. No leaks should be visible.
Smoke test: Introduce smoke into the system to detect gas leaks. This test is rarely used in RVs.
7.3 Verification of Backflow Prevention Devices
Visually inspect the check valve to ensure it is not obstructed.
Test the backflow preventer by closing the isolation valves and checking the pressure in the intermediate zone.
8. Practical Calculations for the Exam
8.1 Calculating Tank Capacity
Capacity (litres) = Length (m) × Width (m) × Height (m) × 1000.
Example: A rectangular tank measuring 0.6 m × 0.4 m × 0.3 m has a capacity of 0.6 × 0.4 × 0.3 × 1000 = 72 litres.
8.2 Calculating Pump Flow Rate
Flow rate (L/min) = Volume (L) / Time (min).
Example: A pump fills an 80 L tank in 6 minutes. Flow rate = 80 / 6 ≈ 13.3 L/min.
8.3 Unit Conversions
1 inch = 25.4 mm
1 foot = 0.3048 m
1 imperial gallon = 4.546 L
1 US gallon = 3.785 L
1 psi = 6.895 kPa
1 bar = 100 kPa ≈ 14.5 psi
8.4 Calculating Pump Discharge Pressure
The maximum pressure of a pump is often given in feet of water head. Pressure (psi) = Head (feet) / 2.31.
Example: A pump with a head of 30 feet can produce a pressure of 30 / 2.31 ≈ 13 psi. This is insufficient for an RV; you need a pump with a head of at least 80 feet (≈ 35 psi).
9. Preventive Maintenance and Troubleshooting
9.1 Common Problems and Solutions
| Problem | Probable Cause | Solution |
|---|---|---|
| Low water pressure | Clogged filter, faulty pump, leak | Clean the filter, test the pump, inspect the pipes |
| Pump cycling (starts and stops) | Leak in the system, pressure switch misadjusted | Find and fix leaks, adjust the pressure switch |
| Hammering noise (water hammer) | Pressure too high, missing shock arrestor | Install a water hammer arrestor, reduce pressure |
| Sewer odour in the RV | Dried-out trap, blocked vent, tank too full | Fill the traps, clean the vent, drain the tank |
| Black water tank won't empty | Blocked valve, pipe obstruction | Open the valve manually, use a drain hose |
| Water heater leaking | Consumed anode, perforated tank | Replace the anode, replace the water heater |
| Insufficient hot water | Faulty heating element, thermostat misadjusted | Test the element, adjust the thermostat |
9.2 Recommended Maintenance Schedule
Each use: Empty the wastewater tanks, check for visible leaks.
Monthly: Test the pump, check pressure, clean filters.
Annually: Inspect the water heater anode, disinfect the water tank, check backflow prevention devices, lubricate valves.
Before winterization: Perform the complete winterization procedure.
10. Pitfalls to Avoid (Red Seal Exams)
156.Confusing grey water and black water: Black water requires chemical treatment and separate draining.
157.Forgetting the water heater bypass during winterization: Antifreeze must never enter the water heater.
158.Using toxic antifreeze (ethylene glycol): Only propylene glycol is safe for food contact.
159.Neglecting the slope of drainage pipes: A slope that is too shallow causes blockages; a slope that is too steep causes trap siphonage.
160.Installing a check valve instead of a backflow preventer: A check valve does not protect against backflow caused by downstream pressure. A backflow preventer is required on the city water connection.
161.Confusing the temperature and pressure relief valve (T&P) with a simple pressure relief valve: The T&P protects against both.
162.Ignoring the trap water seal rule: It must be between 50 mm and 100 mm.
163.Using PVC pipes for hot water: Standard PVC does not withstand temperature; you need CPVC or PEX.
164.Not venting holding tanks: Without venting, negative pressure prevents complete draining.
165.Forgetting to close the gas valve before working on the water heater: Risk of fire or explosion.
11. Summary
An RV's plumbing system includes a pressurized potable water circuit and a gravity drainage circuit.
The key standards are CSA B45 (plumbing fixtures), CSA Z240.2 (RV construction), and the National Plumbing Code (NPC).
Potable water protection is paramount: use backflow prevention devices (backflow preventer) on the city connection and a check valve on the pump.
The water heater must be equipped with a T&P valve and a sacrificial anode.
Drainage slopes must be at least 1/4" per foot for pipes 2" and smaller.
Each fixture must have a trap with a water seal of 50 to 100 mm, vented by a pipe or an AAV.
Winterization involves draining, purging with compressed air, and injecting propylene glycol antifreeze.
Air leak tests (50 psi, max drop of 2 psi in 15 min) and water tests are mandatory.
Master unit conversions and calculations for capacity, flow rate, and pressure.
12. Self-Assessment Questions (Exam-Type)
177.What is the minimum slope for a 1 ½" drainage pipe?
a) 1/8" per foot
b) 1/4" per foot
c) 1/2" per foot
d) 3/4" per foot
(Answer: b)
183.Which device is mandatory on an RV's city water connection?
a) A check valve
b) A backflow preventer
c) A T&P valve
d) A pressure regulator
(Answer: b)
189.During winterization, what should be done with the water heater?
a) Fill it with antifreeze
b) Drain it and bypass it
c) Leave it connected
d) Heat it while empty
(Answer: b)
195.The water seal of a trap must be at least:
a) 25 mm
b) 50 mm
c) 75 mm
d) 100 mm
(Answer: b)
201.A rectangular tank measures 0.8 m × 0.5 m × 0.4 m. What is its capacity in litres?
a) 100 L
b) 120 L
c) 160 L
d) 200 L
(Answer: c)
207.What is the maximum recommended pressure for an RV plumbing system?
a) 30 psi
b) 50 psi
c) 80 psi
d) 100 psi
(Answer: b)
213.The air leak test for a water supply system should be performed at:
a) 30 psi
b) 50 psi
c) 80 psi
d) 100 psi
(Answer: b)
219.What type of antifreeze is safe for the potable water circuit?
a) Ethylene glycol
b) Methanol
c) Propylene glycol
d) Calcium chloride
(Answer: c)
225.The T&P valve on a water heater opens at a maximum temperature of:
a) 60 °C
b) 80 °C
c) 99 °C
d) 120 °C
(Answer: c)
231.A 3" drainage pipe must have a minimum slope of:
a) 1/8" per foot
b) 1/4" per foot
c) 1/2" per foot
d) 3/4" per foot
(Answer: a)
This chapter provides you with the essential knowledge to succeed in the plumbing section of the Red Seal exam. Carefully review the cited NPC rules and practice with the calculations. Good luck with your preparation!
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