Piping, Tubing, and Fittings Installation

Installation of Pipes, Tubes, and Fittings

Chapter Introduction

This chapter covers the installation of pipes, tubes, and fittings for natural gas and propane systems, in accordance with the Canadian Natural Gas and Propane Installation Code (CSA B149.1). As a gasfitter Class B, you must master the principles of sizing, assembly methods, support requirements, and testing procedures. This chapter specifically prepares you for Red Seal exam questions on these topics.

Authorized Piping Materials

Steel Pipes

Carbon steel is the most common material for gas installations. The applicable standards are:

ASTM A53: black steel pipes, welded or seamless

ASTM A106: seamless steel pipes for high-temperature service

ASTM A135: electrically welded steel pipes

Steel pipe must be seamless or electrically welded, and must be designated by its nominal diameter (DN) and wall thickness (gauge or "schedule"). For gas installations, the minimum schedule is generally Schedule 40.

Nominal Diameter (DN)	Outside Diameter (mm)	Schedule 40 Thickness (mm)
15 mm (1/2 in)	21.3	2.77
20 mm (3/4 in)	26.7	2.87
25 mm (1 in)	33.4	3.38
32 mm (1 1/4 in)	42.2	3.56
40 mm (1 1/2 in)	48.3	3.68
50 mm (2 in)	60.3	3.91

Copper Tubing

Copper is permitted for natural gas and propane installations under certain conditions. Types K and L are acceptable; Type M is prohibited for gas. Copper must be marked in accordance with ASTM B88.

Important Restriction: copper may only be used if the gas contains no more than 0.3 grains of hydrogen sulfide (H₂S) per 100 cubic feet (0.7 mg/100 L). This condition is generally met for commercial natural gas but must be verified for propane.

Polyethylene (PE) Tubing

Polyethylene is used for underground piping. It must comply with CSA B137.4. PE is marked by its standard dimension ratio (SDR) , typically SDR 11 or SDR 15.5.

SDR	Maximum Service Pressure (kPa)
11	700
15.5	400

Fittings and Threads

Malleable steel (malleable iron) fittings are the most common. Threads must conform to ASME B1.20.1 (NPT — National Pipe Thread). NPT thread is a tapered thread (1°47' inclination) that achieves sealing through thread deformation.

Pipe Sizing Rules

Fundamental Principles

Gas pipe sizing is based on three parameters:

25.Available supply pressure

26.Allowable pressure drop (pressure loss)

27.Required flow rate in m³/h or ft³/h

The basic formula for flow in a pipe is:

Q = 0.040 × D² × √(ΔP / (L × G))

Where:

Q = flow rate in m³/h

D = inside diameter in mm

ΔP = pressure drop in Pa

L = equivalent length in m

G = relative density of the gas (0.60 for natural gas, 1.50 for propane)

Equivalent Length

Equivalent length accounts for pressure losses caused by fittings. Each fitting adds a fictitious length of straight pipe.

Fitting Type	Equivalent Length (m) for DN 25 mm
90° Elbow	0.9
45° Elbow	0.5
Tee (straight through)	0.6
Tee (branch)	1.5
Valve (gate)	0.3

Sizing Procedure

40.Determine the total load by adding the ratings of all appliances (in kW or BTU/h).

41.Convert the load to flow rate: 1 kW ≈ 0.095 m³/h of natural gas (HHV of 37.5 MJ/m³).

42.Calculate the total equivalent length of the longest run.

43.Use the sizing tables in CSA B149.1 (Annex A) or calculate using the formula above.

44.Check the pressure drop: it must not exceed 0.5 in of water column (125 Pa) for low-pressure installations (less than 7 kPa).

Calculation Example

Given: A residence requires 120,000 BTU/h (35 kW). The total run length is 20 m, with 4 — 90° elbows and 1 branch tee. Supply pressure: 7 kPa (2 in water column).

Step 1: Required flow rate = 35 kW × 0.095 = 3.3 m³/h

Step 2: Equivalent length = 20 + (4 × 0.9) + (1 × 1.5) = 25.1 m

Step 3: With ΔP = 125 Pa, G = 0.60, L = 25.1 m, Q = 3.3 m³/h:

D² = Q / (0.040 × √(ΔP / (L × G))) = 3.3 / (0.040 × √(125 / (25.1 × 0.60)))

D² = 3.3 / (0.040 × √(8.31)) = 3.3 / (0.040 × 2.88) = 3.3 / 0.115 = 28.7

D = √28.7 = 5.36 mm

This result indicates a very small diameter, which shows that the 125 Pa pressure drop is very generous for this flow rate. In practice, you would use the code tables. For 3.3 m³/h over 25 m, a DN 15 mm (1/2 in) pipe would generally be sufficient, but you would choose DN 20 mm (3/4 in) to account for future expansions.

Assembly Methods

Threaded Assembly

Threading of steel pipes must be done with an appropriate die. Key requirements:

The thread must be clean, complete, and free of burrs

Use a joint compound (pipe dope) approved for gas, or PTFE tape (Teflon)

Never use hemp or non-certified joint compound

The compound must be applied to the male threads only, leaving the first two threads free

Tightening must be done with a wrench, with a minimum of 3 threads visible after tightening

CSA B149.1 Rule 6.4.1: All threaded joints must be made gas-tight using a suitable joint compound or tape.

Welded Assembly

Welding is permitted for steel pipes larger than DN 50 mm (2 in). Welders must be certified to CSA W47.1 or hold an equivalent certificate.

Welded joints must be:

Full penetration for butt welds

Free of porosity and cracks

Visually inspected around the entire circumference

Brazed Assembly (Copper)

Brazing of copper uses a high-temperature alloy (typically copper-phosphorus alloy with at least 15% silver). Brazing temperature exceeds 450 °C.

Key Points:

The tube must be degreased and cleaned before brazing

Use an appropriate flux if required (for alloys without phosphorus)

Filler metal penetration must be visible around the entire circumference

Cool slowly to avoid thermal stress

Electrofusion Assembly (Polyethylene)

Electrofusion uses an electric fitting that melts the PE and creates a homogeneous bond. This method is reserved for underground piping.

Procedure:

80.Clean and scrape the tube ends

81.Align the pieces in the fitting

82.Connect the electrofusion machine

83.Respect the fusion and cooling times specified by the manufacturer

Supports and Anchors

Support Spacing

Support spacing depends on the material and diameter of the pipe.

Nominal Diameter	Steel (m)	Copper (m)
15 mm (1/2 in)	1.8	1.2
20 mm (3/4 in)	2.1	1.5
25 mm (1 in)	2.4	1.8
32 mm (1 1/4 in)	2.7	2.1
40 mm (1 1/2 in)	3.0	2.4
50 mm (2 in)	3.0	2.4

CSA B149.1 Rule 6.10.1: Pipes must be supported at intervals not exceeding those indicated above, and supports must be made of corrosion-resistant material.

Support Requirements

Supports must be rigid and securely fastened to the structure

Use pipe clamps with rubber liners to prevent corrosion from contact

Vertical pipes must be supported at each floor or at least every 3 m

Supports must not obstruct joints or fittings

Thermal Expansion

Gas pipes undergo thermal expansion. For steel, the coefficient of expansion is 11.7 × 10⁻⁶ / °C. A temperature change of 50 °C on a 10 m pipe produces an expansion of:

ΔL = 11.7 × 10⁻⁶ × 50 × 10 = 0.00585 m = 5.85 mm

This expansion is generally absorbed by changes in direction. For long straight runs, provide expansion loops or compensators.

Specific Installation Rules

Wall and Floor Penetrations

Pipes passing through walls or floors must be protected by a sleeve (conduit)

The space between the pipe and the sleeve must be sealed with a non-combustible material

Pipes must not be embedded in concrete without corrosion protection

For fire-rated walls, use certified fire-stop sleeves

Underground Piping

For underground piping:

The minimum depth is 450 mm (18 in) below the finished surface

The pipe must be laid on a sand bed of at least 100 mm

Backfill must be free of stones and sharp debris

A warning tape must be placed 300 mm above the pipe

Joints must be accessible for inspection during backfilling

Exposed Piping

Exposed pipes must be installed with a slope of 1% toward the drain point or meter

Pipes must not be installed in ventilation shafts, chimneys, or inaccessible crawl spaces

The minimum distance between a gas pipe and an electrical conduit is 50 mm (2 in) for parallel installations

Appliance Connections

Each appliance must be connected with an approved flexible connector if movement is possible

The flexible connector must have a maximum length of 1.5 m (5 ft) for domestic appliances

An individual shut-off valve must be installed at each appliance

The valve must be accessible and located within 1.8 m of the appliance

Testing and Commissioning

Leak Test

Every installation must undergo a leak test before being put into service.

Installation Type	Test Pressure	Minimum Duration
Low pressure (≤ 7 kPa)	14 kPa (2 psi)	15 minutes
Medium pressure (7–70 kPa)	1.5 × service pressure	15 minutes
High pressure (> 70 kPa)	1.5 × service pressure	30 minutes

CSA B149.1 Rule 6.22.1: The test must be performed with air or an inert gas. Natural gas or propane must never be used for testing.

Test Procedure

129.Close all valves and cap all open ends

130.Pressurize slowly the system to the test pressure

131.Allow the pressure to stabilize (5 minutes minimum)

132.Apply soapy solution to all joints and fittings

133.Observe for bubbles: any bubble indicates a leak

134.Maintain the pressure for the required duration

135.Release the pressure and purge the system

System Purging

After testing, the system must be purged to remove air before commissioning.

Purging must be done with the service gas (natural gas or propane)

Purging must be done to the exterior of the building

Never purge indoors or near an ignition source

Use a gas detector to confirm the purge is complete (≥ 90% gas)

Common Pitfalls to Avoid

144.Confusing test pressure and service pressure: test pressure is always higher than service pressure. Never test a system at service pressure only.

145.Using Type M copper: only Type K or L copper is permitted for gas. Type M has a thinner wall and is not approved.

146.Forgetting equivalent length: when sizing, failing to account for fittings leads to undersizing. Always add equivalent lengths.

147.Neglecting pipe slope: horizontal pipes must have a 1% slope to allow condensate drainage and facilitate purging.

148.Using hemp with joint compound: hemp is not permitted for gas joints. Use only approved compounds.

149.Over-tightening threaded fittings: excessive tightening can crack malleable iron fittings. Respect the recommended torque.

150.Installing pipes in a ventilation shaft: this is prohibited by the code. Gas pipes must be in accessible, ventilated spaces.

151.Forgetting the warning tape for underground piping: this is a mandatory code requirement.

152.Purging indoors: purging must always be done to the exterior. This is a critical safety issue.

153.Not verifying joint compound compatibility: some compounds are attacked by propane. Check approval for the specific gas.

Summary

Authorized materials for gas piping are carbon steel (Schedule 40 minimum), Type K or L copper, and polyethylene for underground installations.

Sizing is based on required flow rate, equivalent length, and allowable pressure drop (125 Pa for low pressure).

Assembly methods are threading (with approved joint compound), welding (CSA W47.1 certified welders), brazing (copper), and electrofusion (PE).

Support spacing ranges from 1.2 m to 3.0 m depending on material and diameter.

Underground piping requires a minimum depth of 450 mm, a sand bed, and warning tape.

Leak testing is done with air or inert gas, never combustible gas. Test pressure is 14 kPa for low-pressure installations.

Purging must be done to the exterior using the service gas.

Self-Assessment Questions

165.What is the minimum schedule for steel pipe in a gas installation?

166.What is the minimum test pressure for a low-pressure installation?

167.Which type of copper is prohibited for gas installations?

168.What is the minimum burial depth for a gas pipeline?

169.What is the maximum support spacing for a DN 20 mm steel pipe?

170.What is the maximum length of a flexible connector for a domestic appliance?

171.What gas can be used for leak testing?

172.What is the minimum slope required for horizontal pipes?

Answers: 1) Schedule 40; 2) 14 kPa; 3) Type M; 4) 450 mm; 5) 2.1 m; 6) 1.5 m; 7) Air or inert gas; 8) 1%.

Normative References

CSA B149.1: Natural Gas and Propane Installation Code

CSA B137.4: Polyethylene (PE) tubing and fittings for gas

ASTM B88: Specification for seamless copper water tube

ASTM A53: Specification for black steel pipe

ASME B1.20.1: Pipe threads (NPT)

CSA W47.1: Certification of welding companies

This chapter covers the essential knowledge required for the Red Seal gasfitter Class B exam regarding the installation of pipes, tubes, and fittings. Make sure you master the sizing tables, leak test rules, and support requirements before moving on to the exam.