Water Systems, Plumbing, and Drainage

Chapter Introduction

This chapter covers the essential knowledge related to potable water supply systems, drainage and venting networks, and the appliances connected to them. For the Red Seal exam, you must master basic hydraulic principles, Canadian plumbing standards, installation methods, and diagnostic procedures specific to water-using appliances (dishwashers, washing machines, refrigerators with water dispensers, etc.).

The content in this chapter is based on the National Plumbing Code of Canada (NPC) and applicable CSA standards. No provincial content is included; requirements specific to your province must be verified with the authority having jurisdiction.

Fundamental Principles of Applied Hydraulics

Pressure, Flow Rate, and Pressure Drop

Pressure in a water system is expressed in kilopascals (kPa) or pounds per square inch (psi). The relationship between these units is: 1 psi ≈ 6.895 kPa. Normal static pressure in a municipal system ranges between 350 and 550 kPa (50 to 80 psi).

Flow rate (Q) is the volume of water flowing per unit of time, expressed in litres per minute (L/min) or litres per second (L/s). The fundamental relationship is:

Q = A × V

where A is the cross-sectional area of the pipe (in m²) and V is the flow velocity (in m/s).

Pressure drop (ΔP) is the decrease in pressure due to friction in pipes, elbows, fittings, and valves. It increases with pipe length, internal wall roughness, and water velocity. For effective troubleshooting, remember that excessive pressure drop manifests as reduced flow at faucets and appliances.

Static Pressure, Dynamic Pressure, and Water Hammer

Static pressure is the pressure measured when water is at rest. Dynamic pressure (or service pressure) is measured during flow; it is always lower than static pressure due to pressure losses.

Water hammer is a transient overpressure caused by the sudden stoppage of flow (rapid closure of a solenoid valve). This pressure wave can reach several times the normal pressure and damage pipes, fittings, and solenoid valves. Modern appliances (dishwashers, washing machines) are equipped with anti-water-hammer devices or require the installation of dampeners (suppressors) on the piping.

Temperature and Thermal Expansion

Hot water expands. In a closed system (presence of a backflow preventer), thermal expansion can cause pressure to rise above static pressure. An expansion tank must be installed on the cold water side of the water heater to absorb this expansion. The pre-charge pressure of the tank must be set to the system static pressure (typically 350 kPa).

Potable Water Supply

Supply Piping: Materials and Sizing

The following table summarizes commonly encountered piping materials and their characteristics:

Material	Common Sizes	Typical Use	Characteristics
Copper Type M	12.7 mm (1/2 in) to 50.8 mm (2 in)	Hot and cold water	Lightweight, easy to bend; soldering required
Copper Type L	12.7 mm to 50.8 mm	Hot and cold water (thicker)	Better pressure resistance
PEX (cross-linked polyethylene)	12.7 mm to 31.8 mm	Hot and cold water	Flexible, freeze-resistant, compression or expansion fittings
CPVC (chlorinated polyvinyl chloride)	12.7 mm to 31.8 mm	Hot and cold water	Rigid, solvent-cemented
Galvanized steel	12.7 mm to 50.8 mm	Cold water (older installations)	Possible internal corrosion; reduced flow with age

Important Rule: PEX must not be exposed to direct UV rays. It must be protected when installed outdoors or near a window. Additionally, PEX fittings must not be used inside a wall without access (some jurisdictions require this; check the local code).

Sizing Supply Pipes

Sizing is based on the number of fixture units (fu) assigned to each appliance. The table below shows typical NPC values:

Fixture	Fixture Units (cold water)	Fixture Units (hot water)	Minimum Flow Rate (L/min)
Dishwasher	1.4	1.4	8.3
Washing machine	1.4	1.4	8.3
Refrigerator with dispenser	0.6	0	3.8
Kitchen sink	1.4	1.4	8.3
Bathtub	1.4	1.4	8.3
Shower	1.4	1.4	8.3
Toilet (tank)	2.2	0	5.7
Exterior hose bib	2.2	0	5.7

The total probable flow is calculated using the Hunter method (probability curves). For the exam, you must know that the probable flow is never the arithmetic sum of the flow rates of all fixtures; it is always lower, because not all fixtures operate simultaneously.

Shut-off Valves and Faucets

Each water-connected appliance must have an accessible individual shut-off valve. Ball valves provide complete and reliable shut-off. Seat valves (compression type) are common but can leak at the stem.

The backflow preventer is mandatory on potable water circuits to prevent contamination by backflow (reverse siphoning). Appliances such as dishwashers must be protected by an air gap or a backflow preventer conforming to CSA B64.

Drainage and Venting Systems

Gravity Drainage Principles

Drainage relies on the slope of pipes. The minimum slope for a drainage pipe is 2% (2 cm per metre) for diameters of 75 mm (3 in) and less, and 1% for larger diameters. Excessive slope (more than 4%) can allow water to flow too quickly and leave solids behind, causing blockages.

Drainage Pipes: Materials

Material	Sizes	Use	Characteristics
PVC (polyvinyl chloride)	38 mm to 152 mm	Drainage and venting	Lightweight, solvent-cemented; chemical resistant
ABS (acrylonitrile butadiene styrene)	38 mm to 152 mm	Drainage and venting	Similar to PVC, but more impact-resistant
Cast iron	50 mm to 152 mm	Drainage (commercial buildings)	Excellent acoustic insulation; heavy
Copper	38 mm to 76 mm	Drainage (rare)	Used in high-end renovations

Drainage System Venting

Venting has three functions: equalizing pressures in the system, venting decomposition gases, and allowing wastewater to flow. An unvented drainage system creates siphons that suck water out of floor drains (traps), allowing gases into the living space.

The following table summarizes vent types:

Vent Type	Description	Main Requirement
Primary vent	Extension of the soil stack above the roof	Diameter ≥ 1/2 of the stack diameter
Secondary vent	Connected to the soil stack above the highest fixture	Slope ≥ 1% towards the stack
Circuit vent	Connected to a group of fixtures (maximum 8)	Minimum diameter 38 mm
Individual vent	Each fixture has its own vent	Connected to the main stack

Key Rule: The floor drain (trap) must have a water seal of at least 50 mm and no more than 100 mm. An insufficient water seal allows gases to pass; an excessive seal slows flow and promotes debris buildup.

Soil Stack and Building Drain

The soil stack is the main vertical column that collects wastewater from upper floors. The building drain is the horizontal portion that carries wastewater to the municipal sewer or septic tank. The building drain must have a minimum diameter of 100 mm (4 in) for a residence.

Connecting Household Appliances

Dishwasher

Connecting a dishwasher involves three connections: hot water supply, drainage, and electricity.

Water Supply:

Connection to the hot water branch of the kitchen sink.

Supply line in flexible copper or PEX, with an accessible shut-off valve.

Supply pressure: 140 to 800 kPa (20 to 116 psi). Above 800 kPa, a pressure-reducing valve is required.

Water temperature: 49 °C to 60 °C (120 °F to 140 °F). A temperature above 60 °C can damage plastic components and cause burns.

Drainage:

The drain hose must form an anti-siphon loop (high loop) of at least 800 mm above the floor before connecting to the sink drain or garbage disposal.

Connection to the disposal must be made with a special adapter; the dishwasher drain hose must never be inserted directly into the drainage pipe without backflow protection.

The minimum diameter of the drain hose is 19 mm (3/4 in).

Troubleshooting Checks:

Water leak under the appliance: check the water supply connections, door gasket, drain pump, and inner tub.

Poor drainage: check the anti-siphon loop, hose blockage, disposal check valve, and pump.

Unusual noise: check pump bearings, debris in the wash chamber, and supply pressure.

Washing Machine

Water Supply:

Two shut-off valves (hot and cold water) with 19 mm (3/4 in) threaded connections.

Supply hoses in reinforced rubber or braided steel. Rubber hoses should be replaced every 5 years (manufacturer recommendation).

Minimum pressure: 140 kPa. Maximum pressure: 800 kPa.

Minimum flow rate: 8.3 L/min per valve.

Drainage:

The drain hose must be inserted into a wall standpipe with a minimum diameter of 38 mm (1.5 in) and a height of 600 to 900 mm above the floor.

The washing machine drain hose must be secured to prevent it from dislodging during drainage (discharge pressure).

The height of the upper bend of the drain hose must be higher than the maximum water level in the tub to prevent backflow.

Leak Diagnosis:

Leak at the valve: worn washers or gaskets.

Leak at the supply hose: cracks (aged rubber), loose connections.

Leak under the machine: drain pump gasket, tub gasket, punctured drain hose.

Refrigerator with Water and Ice Dispenser

Water Connection:

6.35 mm (1/4 in) copper or PEX tubing.

Dedicated shut-off valve, typically installed on the cold water branch.

Pressure: 280 to 550 kPa (40 to 80 psi). Pressure below 280 kPa results in insufficient flow and hollow ice cubes.

The tubing must not be installed near heat sources (oven, water heater).

Water Filter:

Modern refrigerators are equipped with a filter certified to NSF/ANSI 42 or 53.

The filter must be replaced according to manufacturer recommendations (typically every 6 months or after 2,000 L).

A clogged filter reduces flow and can cause leaks at the filter housing.

Diagnosing Common Problems:

Reduced flow: clogged filter, pinched tubing, partially closed valve, insufficient supply pressure.

Leak at the dispenser: worn dispenser door gasket, solenoid valve not closing completely.

Hollow or small ice cubes: insufficient pressure, clogged filter, freezer temperature too high.

Water Heaters and Hot Water Systems

Types of Water Heaters

Type	Typical Capacity	Efficiency	Characteristics
Gas storage tank	150 to 300 L	60 to 70%	Venting required (chimney or direct vent)
Electric storage tank	150 to 300 L	95 to 100%	Simple to install; higher operating cost
Tankless (instantaneous)	—	85 to 98%	Limited flow rate; critical sizing
Condensing	150 to 300 L	90 to 98%	Acidic condensate drainage required

Temperature and Pressure Relief Valve (T&P)

The T&P valve is a mandatory safety device on all storage tank water heaters. It opens if the temperature exceeds 99 °C or if the pressure exceeds the tank's rated pressure (typically 1,034 kPa or 150 psi).

Installation Requirements:

The valve must be installed on the top or side of the tank, within the top 150 mm.

The discharge tube must be copper or CPVC, have a diameter equal to or greater than the valve outlet, and terminate 150 to 300 mm above the floor, without threads at the end.

The discharge tube must not be connected to the drainage system; it must discharge freely.

Testing the Valve: Lift the lever manually to verify operation. If the valve does not reseat completely or leaks after testing, it must be replaced.

Thermal Expansion and Expansion Tank

When the system is equipped with a backflow preventer or pressure-reducing valve, thermal expansion of hot water cannot be absorbed by the system. Pressure can then exceed the tank's rated pressure, causing the T&P valve to open.

The expansion tank must be:

Installed on the cold water line, between the backflow preventer and the water heater.

Sized according to the water heater tank volume and the system static pressure.

Pre-charged to the system static pressure (verify with a pressure gauge).

Hot Water Temperature

The recommended temperature is 49 °C (120 °F) for residential use, to prevent burns while ensuring sufficient comfort. A temperature above 60 °C (140 °F) accelerates tank corrosion and increases the risk of serious burns.

Burn Time Calculation (know this for the exam):

Water Temperature	Time for 3rd Degree Burn (adult)
49 °C (120 °F)	More than 10 minutes
52 °C (125 °F)	2 to 5 minutes
55 °C (130 °F)	30 seconds
60 °C (140 °F)	5 seconds
65 °C (150 °F)	2 seconds

Applicable Codes and Standards

National Plumbing Code of Canada (NPC)

The NPC is the primary reference for plumbing system installation. The relevant sections for appliance servicing are:

Section 2: Definitions and interpretations.

Section 3: Characteristics of materials and appliances.

Section 6: Potable water supply.

Section 7: Drainage and venting systems.

Section 8: Hot water (water heaters, T&P valves, expansion tanks).

Relevant CSA Standards

Standard	Subject
CSA B45	Ceramic plumbing fixtures
CSA B64	Backflow prevention devices
CSA B125	Plumbing fittings
CSA C22.2 No. 120	Household appliances (electrical safety)
CSA C22.1	Canadian Electrical Code, Part I — for electrical connections

Canadian Electrical Code (CE Code)

The Canadian Electrical Code, Part I (C22.1) applies to the electrical connections of appliances. Relevant rules include:

Rule 26-700: Connection of household appliances.

Rule 26-704: Dishwashers — grounding and ground fault circuit interrupter (GFCI) protection requirements.

Rule 26-706: Washing machines — grounding requirements.

Key Requirement: Dishwashers and washing machines must be protected by a ground fault circuit interrupter (GFCI) rated at 5 mA, in accordance with Rule 26-704 of the CE Code.

Diagnostic and Repair Procedures

Checking Water Pressure

130.Close all fixtures in the installation.

131.Install a pressure gauge on a shut-off valve (for example, the washing machine valve).

132.Open the valve and read the static pressure.

133.Open another fixture (for example, the kitchen sink) and read the dynamic pressure.

134.The difference between the two readings indicates the system pressure drop.

Interpretation:

Static pressure < 140 kPa: municipal supply problem or obstructed piping.

Dynamic pressure < 140 kPa with normal static pressure: undersized piping, obstructions, partially closed valve.

Pressure > 800 kPa: install a pressure-reducing valve.

Flow Rate Test

Flow rate is measured with a flow meter or by the timed bucket method:

141.Open the faucet fully.

142.Fill a 10 L bucket while timing the duration.

143.Calculate the flow rate: Q (L/min) = 10 L ÷ time (min).

Example: if the bucket fills in 45 seconds (0.75 min), the flow rate is 10 ÷ 0.75 = 13.3 L/min.

Leak Detection

Visible leak: inspect fittings, joints, pipes, and hoses.

Hidden leak: use a moisture meter, thermal imaging camera, or pressure test.

Pressure test: close the shut-off valve, install a pressure gauge, pressurize the circuit to 700 kPa, and observe the pressure drop over 30 minutes. A drop of more than 10 kPa indicates a leak.

Replacing a Solenoid Valve

The solenoid valve is a critical component in dishwashers, washing machines, and refrigerators. Procedure:

151.Disconnect the power supply and close the water shut-off valve.

152.Disconnect the electrical connections (note the wire colours).

153.Remove the water supply lines.

154.Remove the solenoid valve from its bracket.

155.Install the new solenoid valve (verify compatibility: voltage, flow rate, thread type).

156.Restore the water supply and check for leaks.

157.Restore the power and test the cycle.

Solenoid Valve Verification:

Measure the coil resistance with a multimeter (typically 20 to 200 Ω depending on the model).

Check the continuity of the control circuit.

Check for debris in the valve seat (a common cause of residual leakage).

Pitfalls to Avoid

164.Confusing static and dynamic pressure: Dynamic pressure is always lower. A diagnosis based solely on static pressure can miss a pressure drop problem.

165.Forgetting the dishwasher anti-siphon loop: A drain hose without a high loop causes wastewater backflow into the appliance.

166.Neglecting the expansion tank pre-charge: A tank pre-charged to the wrong pressure does not perform its function, and the T&P valve opens.

167.Using PEX exposed to UV: PEX degrades quickly in direct light; it must be protected or replaced with copper.

168.Ignoring the 50 mm water seal rule: A trap with an insufficient water seal allows sewer gases to pass.

169.Over-tightening PEX fittings: PEX compression fittings have a specific torque; over-tightening damages the pipe and causes leaks.

170.Not checking the hot water temperature: Excessive temperature (> 60 °C) is a burn hazard and accelerates water heater corrosion.

171.Forgetting the GFCI for appliances near water: Rule 26-704 of the CE Code requires a 5 mA GFCI for dishwashers and washing machines.

172.Confusing nominal and actual diameters: The nominal diameter (DN) of a pipe does not always correspond to the actual inside diameter. Check the manufacturer's specifications.

173.Not checking the drainage pipe slope: Insufficient slope (< 1%) causes blockages; excessive slope (> 4%) leaves solids behind.

Summary

Pressure is measured in kPa; normal residential system pressure is 350 to 550 kPa.

Flow rate is calculated with Q = A × V; the probable flow of an installation is determined by the Hunter method, never by simple addition.

Water hammer is caused by the sudden stoppage of flow; dampeners are required on solenoid valve circuits.

Common piping materials are copper (Types M and L), PEX, CPVC, and galvanized steel (older).

Drainage operates by gravity with a slope of 1 to 2%; venting is essential to prevent siphoning.

The floor drain (trap) must have a water seal of 50 to 100 mm.

The dishwasher requires an 800 mm anti-siphon loop and backflow protection.

The washing machine connects to 19 mm valves with reinforced hoses; the drain hose must be inserted into a standpipe of 38 mm minimum.

The refrigerator with dispenser requires a pressure of 280 to 550 kPa and a filter certified to NSF/ANSI 42 or 53.

The T&P valve is mandatory on all storage tank water heaters; its discharge tube must discharge freely 150-300 mm above the floor.

The expansion tank is required in the presence of a backflow preventer; it must be pre-charged to the static pressure.

The National Plumbing Code of Canada and the Canadian Electrical Code, Part I are the primary regulatory references.

5 mA GFCIs are mandatory for dishwashers and washing machines (Rule 26-704).

Review Questions (Self-Assessment)

191.What is the normal static pressure of a residential municipal system?

192.A 75 mm drainage pipe must have a minimum slope of how much?

193.What is the minimum water seal of a floor drain (trap)?

194.What is the minimum height of the dishwasher anti-siphon loop?

195.What is the minimum pressure required for a refrigerator water dispenser?

196.At what temperature must the T&P valve open?

197.Which CE Code rule requires a GFCI for dishwashers?

198.How do you calculate flow rate using the timed bucket method?

199.What is the minimum diameter of a washing machine wall standpipe?

200.Why is an expansion tank necessary in the presence of a backflow preventer?

Regulatory References

National Plumbing Code of Canada (NPC) — Canadian Commission on Building and Fire Codes.

CSA B64 — Backflow prevention devices and vacuum breakers.

CSA B125 — Plumbing fittings.

CSA C22.1 — Canadian Electrical Code, Part I.

CSA C22.2 No. 120 — Household appliances.

NSF/ANSI 42 and 53 — Water filters (particulate and contaminant reduction).

Water Systems, Plumbing, and Drainage