Piping and Fittings

Piping and Fittings

Chapter Introduction

This chapter covers all the essential knowledge about pipes, tubes, and fittings that every journeyman plumber must master for the Red Seal exam. You must know not only the physical characteristics of materials, but also their permitted applications, assembly methods, thermal expansion calculations, and the requirements of the Canadian Plumbing Code (CPC) . This chapter is structured to follow the logic of the exam: material identification, selection according to use, installation techniques, and calculations.

2.1 Classification of Pipes and Tubes

2.1.1 Pipe vs. Tube — Fundamental Distinction

The terminology is not interchangeable. A pipe is sized by its nominal inside diameter (ID) and wall thickness (schedule). A tube is sized by its actual outside diameter (OD) and wall thickness in inches or millimetres. This distinction is crucial for fittings: a fitting for a 1/2" pipe does not fit a 1/2" tube.

2.1.2 Piping Materials — Properties and Applications

Carbon Steel (Black) : Used for natural gas and propane (CSA B149.1), water risers, and fire protection systems. High pressure resistance, but susceptible to corrosion. Assembled by threading (up to 4"), welding, or mechanical fittings.

Galvanized Steel : Steel coated with zinc to resist corrosion. Used for potable water (although less and less), compressed air, and open systems. Never use for gas — zinc flakes detach and clog burner orifices. Threading destroys the zinc coating at joints; an approved sealing compound must be applied.

Copper : Available in Types K, L, M, and DWV. Type L is the most common for plumbing. Type K has the thickest wall (underground use). Type M is for moderate pressure applications. DWV is for drainage only (thin wall). Assembled by capillary soldering (soft soldering with tin-antimony 95/5 for potable water), brazing (high-silver alloy) for refrigerant gases, or mechanical fittings (compression, push-to-connect).

PVC (Polyvinyl Chloride) : For drainage, venting, and cold water piping (Type PVC 1120 or 1220, CSA B137.3 standard). Never use for hot water — maximum temperature is 60°C. Assembled by solvent welding (PVC cement).

CPVC (Chlorinated PVC) : For hot and cold water (CSA B137.6). Maximum temperature of 82°C. Assembled with CPVC-specific solvent (orange cement).

PEX (Cross-linked Polyethylene) : For hot and cold potable water (CSA B137.5). Flexible, resists freezing (to a certain extent), does not corrode. Assembled with compression, expansion (Uponor system), or insert-type fittings with a ring. Note : the maximum length of the expansion loop must be calculated.

ABS (Acrylonitrile-Butadiene-Styrene) : For drainage and venting (CSA B181.1). Assembled with solvent (ABS cement). Do not use for potable water.

Cast Iron : For sanitary drainage, soil stacks, and underground piping. Excellent acoustic insulation. Assembled by hub-and-spigot with rubber gasket (husband), or by flanges. CSA B70 standard.

Stainless Steel : For corrosive applications, ultrapure water, steam systems. Assembled by TIG welding or mechanical fittings.

2.2 Fittings — Types and Functions

2.2.1 Threaded Fittings

Threads must conform to ASME B1.20.1 (NPT — National Pipe Thread). NPT threads are tapered (3/4 inch per foot). Sealing is achieved by thread deformation, aided by a sealing product (joint compound, PTFE tape).

Common fittings : 90° and 45° elbows, tee, coupling, reducer, plug, nipple, union, cross (rare, prohibited for gas). A nipple is a short pipe threaded at both ends. A union allows disassembly of a line without cutting the pipe.

Rule of thumb : The number of visible threads after tightening should be 2 to 3 for a 1/2" to 3/4" pipe, and 1 to 2 for larger diameters. Overtightening cracks the fitting or the pipe.

2.2.2 Soldered Fittings (Copper)

Capillary soldering relies on the principle of capillary action: the space between the tube and the fitting (0.004" to 0.006") draws in the molten alloy. The steps are: cutting, reaming/deburring, cleaning (emery cloth), applying flux, assembling, heating, and applying the filler alloy.

Soldering alloys :

Trap : Flux must be applied sparingly. Excess flux can be drawn into the line and contaminate the system. For potable water, use lead-free flux conforming to NSF/ANSI 61.

2.2.3 Compression Fittings

Used for copper, PEX, and stainless steel tubing. A nut and ferrule are compressed onto the tube to create the seal. Do not overtighten — the ferrule deforms and the joint leaks. Two turns after initial contact is generally sufficient.

2.2.4 Push-to-Connect Fittings

Mechanical fittings with a grab ring and an O-ring. Conform to ASSE 1061. They allow rapid assembly without specialized tools. Note : the tube must be cut square and deburred, and inserted to the stop (marked on the fitting). Not suitable for buried applications without protection.

2.2.5 PEX Fittings

Three main systems:

CPC Rule : PEX fittings must conform to CSA B137.5. Fittings must be accessible for inspection, unless installed in accordance with the manufacturer's instructions.

2.3 Calculations and Sizing

2.3.1 Thermal Expansion

All materials expand with heat. The coefficient of linear expansion (α) is expressed in mm/(m·°C).

Calculation formula :

ΔL = α × L × ΔT

Where:

Example : A 12 m copper line is installed at 10°C. Hot water reaches 60°C. ΔT = 50°C. ΔL = 0.0168 × 12 × 50 = 10.08 mm. The line expands by approximately 10 mm. An expansion loop or compensator must be provided.

For PEX : Expansion is so significant that the CPC requires expansion loops every 6 to 8 m for long runs. The loop must have a diameter of at least 8 times the tube diameter.

2.3.2 Pressure Drop and Flow Velocity

Water velocity in piping must not exceed:

Pressure drop (ΔP) depends on diameter, roughness, flow rate, and length. For the exam, you must know how to use the CPC pressure drop tables (Appendix A) or the simplified Hazen-Williams formula:

ΔP (kPa/m) = 10.5 × (Q / C)¹·⁸⁵ / d⁴·⁸⁷

Where:

Trap : Do not confuse nominal diameter with actual inside diameter. A 1" PVC pipe has a different ID than a 1" steel pipe.

2.3.3 Service Pressure and Test Pressure

The maximum service pressure of a pipe depends on its material, temperature, and thickness. Barlow's formula for pressure pipes:

P = (2 × S × t) / D

Where:

CPC Requirement (Rule 2.6.3.1) : All piping must be subjected to a leak test at a pressure of at least 1.5 times the service pressure, but never less than 350 kPa (50 psi) for water, and 100 kPa (15 psi) for gas. The test must be maintained for at least 1 hour without pressure drop.

2.4 Canadian Plumbing Code Requirements

2.4.1 Key Rules for Piping

Rule 2.5.1.1 : Pipes and fittings must conform to applicable CSA standards (B137.x for plastics, B70 for cast iron, etc.). A product without a certification mark (CSA, cUL, etc.) is prohibited.

Rule 2.5.2.1 : Water piping must be supported at maximum intervals:

Rule 2.5.3.1 : Buried piping must be installed at a minimum depth of 1.2 m (to prevent freezing) or at a depth where the soil temperature remains above 0°C. Water lines must be installed at least 300 mm above sewer lines, or 600 mm if they are in the same trench.

Rule 2.5.4.1 : All piping must be accessible for inspection and maintenance. Pipes embedded in walls must be protected against corrosion (sleeve, sheath).

2.4.2 Specific Rules for Gas (CSA B149.1)

CSA B149.1 (Natural Gas and Propane Installation Code) applies to gas piping. Essential points:

Prohibition : PVC, CPVC, ABS, and PEX are prohibited for natural gas and propane. Only steel, copper (with restrictions), and PE (polyethylene) for underground installations are permitted.

2.4.3 Rules for Drainage and Venting

Rule 2.4.3.1 : Minimum slopes for drainage piping:

Rule 2.4.4.1 : Changes in direction must be made with 45° elbows or combinations of elbows, never with 90° elbows for horizontal drainage lines (risk of clogging).

Rule 2.4.6.1 : Each plumbing fixture must be protected by a trap. The distance between the trap and the vent must conform to the CPC tables (maximum length according to diameter).

2.5 Installation Techniques and Procedures

2.5.1 Cutting and Preparing Pipes

Steel : Cut with a hacksaw or pipe cutter. Deburr the inside and outside. For threading, use a die of the correct size with cutting oil. The thread must be clean and free of burrs.

Copper : Cut with a pipe cutter (best result) or a hacksaw. Deburr with a reamer. Clean the outside of the tube and the inside of the fitting with emery cloth. Apply flux immediately before heating.

PVC/CPVC : Cut with a fine-tooth saw or pipe cutter. Chamfer the end (15°) to facilitate insertion. Clean with a primer before applying cement. Cement must be applied to both the pipe and the fitting. Insert with a quarter turn.

PEX : Cut with a specific PEX cutter (shears). The tube must be cut perpendicular. Deburr the inside with the reaming tool. Insert the tube to the fitting stop.

2.5.2 Support and Anchoring

Supports must conform to Rule 2.5.2.1. Supports must:

Anchoring : Anchors (rigid fastenings) are used to control expansion and direct movement toward compensators. Do not confuse a support (carries the weight) with an anchor (restricts movement).

2.5.3 Leak Test — Procedure

For gas : The test is done with compressed air or nitrogen at 100 kPa for 15 minutes. The gauge must be graduated in kPa and have an accuracy of 0.5 kPa.

2.6 Corrosion and Protection

2.6.1 Galvanic Corrosion

When two different metals are in contact in an electrolyte (water), the more anodic metal corrodes. The galvanic series ranks metals from most anodic (sacrificial) to most cathodic (protected).

Rule of thumb : Never directly connect copper to galvanized steel (the zinc will corrode). Use a dielectric fitting (dielectric union or brass nipple with insulating gasket).

2.6.2 Corrosion Protection

2.7 Traps to Avoid

2.8 Exam Tips

2.9 Summary

2.10 Traps to Avoid (Exam Recap)

This chapter covers the essential knowledge for the "Piping and Fittings" section of the Red Seal exam. Review the tables, practice expansion and slope calculations, and memorize the CPC and CSA B149.1 rules. Good luck with your preparation.