Pipe Cutting and Joining

Learning Objectives

Upon completing this chapter, you will be able to:

4.Identify the code-approved methods for cutting and joining each piping material recognized by the 2018 Georgia Plumbing Code (GPC) and 2018 Georgia Gas Code (GGC).

5.Apply the general installation requirements that govern joint preparation, alignment, and pressure testing.

6.Distinguish between joints permitted for sanitary drainage versus those permitted for potable water, and between plumbing and gas piping systems.

7.Recognize the master plumber’s supervisory and liability responsibilities when selecting joining methods on a project.

8.Navigate the relevant chapters and tables of the 2018 GPC and GGC to verify a specific joining method’s legality before installation.

1.1 General Principles of Joint Integrity

The fundamental purpose of any pipe joint is to maintain pressure integrity, prevent leakage, and preserve the internal diameter of the pipe. The 2018 Georgia Plumbing Code (based on the 2018 IPC) establishes that all joints must be watertight and gas-tight for their intended service. For the master plumber, this means more than simply following a manufacturer’s instruction—it means verifying that the joining method is approved for the specific material, service (sanitary, vent, storm, potable, or gas), and pressure condition.

The code requires that all pipe joints be made with fittings that match the pipe material and that the installation follows the manufacturer’s published installation instructions. Where the code and manufacturer instructions conflict, the stricter requirement governs. This is a critical legal distinction: the master plumber is responsible for the final installation, not the manufacturer.

1.2 Cutting Pipe — Preparation Standards

Before any joint is made, the pipe must be cut square and true. The code does not specify cutting methods in detail, but it requires that the cut end be free from burrs and rough edges. Burrs reduce the effective internal diameter, create turbulence, and can damage gaskets or solvent cement joints.

Field practice for the master plumber:

Use a wheel cutter for copper and steel; use a fine-tooth saw or tubing cutter for plastic.

Ream the inside of copper and steel pipe after cutting to remove the burr created by the cutting wheel.

For plastic pipe, chamfer the outside edge at approximately 15° to prevent the solvent cement from being scraped off during assembly.

For cast iron, use a snap cutter or saw; never use a torch to cut pipe that is in service or near combustible material.

The code also requires that the pipe be clean and dry before joining. This is particularly critical for solvent cement joints on PVC and CPVC, where moisture will prevent proper fusion.

1.3 Solvent Cement Joints (Plastic Pipe)

Solvent cement joining applies to PVC, CPVC, and ABS piping systems. The 2018 GPC requires that solvent cement joints conform to the applicable ASTM standards (e.g., D 2564 for PVC, F 493 for CPVC, D 2235 for ABS). The cement must be specifically formulated for the pipe material—using PVC cement on ABS pipe is a violation, and vice versa.

Key code requirements:

The joint must be made by applying primer to the pipe and fitting socket, followed by the cement. The primer softens the plastic; the cement fuses the two surfaces.

The pipe must be inserted fully into the fitting socket, and the joint must be held together for a period sufficient to prevent push-out (typically 15–30 seconds for small diameters).

The code prohibits the use of solvent cement that has been thinned or has exceeded its shelf life.

For CPVC, the code requires that the cement be rated for the elevated temperature service of the system (typically 180°F for hot water).

Exam trap: Many candidates assume that primer is optional for all plastic joints. The code requires primer for PVC and CPVC joints unless the cement is a one-step primer-cement combination specifically listed for that use. ABS joints do not require primer.

1.4 Threaded Joints

Threaded joints are permitted for steel pipe (galvanized and black), brass pipe, and certain plastic pipe where listed. The 2018 GPC requires that threads be cut to the standard taper (NPT) and that the joint be made with a thread-joint compound or tape that is compatible with the service.

Critical code points:

Threads must be clean and full-cut; no more than one thread may be stripped or damaged.

The pipe must be engaged in the fitting so that no more than two threads are exposed beyond the fitting face.

For gas piping (2018 GGC), the code requires that joint compound be applied to the male threads only, and that the compound be resistant to the action of liquefied petroleum gas if the system carries LPG.

Galvanized pipe and fittings must not be field-threaded after the galvanizing has been burned off by cutting with a torch. This is a common violation and a code trap.

Master-level responsibility: The code prohibits the use of threaded joints in concealed locations where leakage would cause damage, unless the joint is accessible. The master plumber must plan the layout to place threaded joints in accessible chases or spaces.

1.5 Soldered and Brazed Joints (Copper)

Soldered joints for copper pipe and tubing are permitted for plumbing systems, but the 2018 GPC restricts their use for potable water to lead-free solder (0.2% lead content maximum). Brazed joints require a filler metal with a melting point above 1000°F.

Code requirements:

Surfaces must be cleaned with abrasive cloth or a wire brush, not with acid flux that cannot be fully removed.

Flux must be applied sparingly and only to the male end of the joint.

The joint must be heated uniformly until the solder flows completely around the joint by capillary action.

For potable water systems, the code requires that the solder be certified as lead-free under NSF/ANSI 61 or equivalent.

Field point: The master plumber must verify that all solder and flux used on potable systems is lead-free. This is not just a code issue—it is a public health liability. The code also prohibits soldered joints in gas piping systems; gas joints must be threaded, flanged, or welded.

1.6 Mechanical Joints and Push-Fit Fittings

Mechanical joints include compression fittings, flared fittings, push-fit (stab) fittings, and grooved couplings. The 2018 GPC permits these where the fitting is listed for the application and installed per the manufacturer’s instructions.

Key distinctions:

Compression fittings are permitted for copper and plastic pipe in accessible locations. They are not permitted in concealed locations unless specifically listed for that use.

Push-fit fittings are listed for copper, CPVC, and PEX. They are permitted for water distribution but must be installed with the pipe fully inserted to the depth mark.

Grooved couplings (e.g., Victaulic-type) are permitted for steel pipe, cast iron, and copper in larger diameters. The code requires that the groove be cut to the manufacturer’s specifications.

Exam trap: The code does not permit mechanical joints for sanitary drainage in concealed locations unless the fitting is accessible. This is a common source of failed inspections.

1.7 Flanged Joints

Flanged joints are used primarily for equipment connections (water heaters, pumps, valves) and for connecting to flanged fixtures. The 2018 GPC requires that flanges be aligned without strain, that gaskets be of a material compatible with the fluid, and that bolts be tightened in a cross-pattern to prevent uneven compression.

For gas piping (2018 GGC), flanged joints are permitted only where the system is designed for them, and the gasket must be resistant to the gas service. The code requires that flanged joints be installed so that they are accessible for inspection and maintenance.

1.8 Welded Joints

Welded joints are permitted for steel pipe in both plumbing and gas systems. The 2018 GPC requires that welding be performed by a qualified welder in accordance with the applicable ASME or AWS standards. For gas piping, the 2018 GGC requires that all welded joints be performed by a welder qualified under ASME Section IX or AWS B2.1.

Code requirements:

The joint must be clean and free of oil, grease, or moisture before welding.

The weld must be free of cracks, incomplete fusion, or porosity.

For gas piping, the code requires that welded joints be visually inspected and, where required, pressure tested to the system test pressure.

Master-level responsibility: The master plumber is responsible for verifying welder qualifications and for ensuring that welding is not performed on pipe containing flammable gas or liquid. This is a safety issue with direct liability.

1.9 Hub-and-Spigot and No-Hub Joints (Cast Iron)

Cast iron soil pipe is joined either by hub-and-spigot (lead and oakum or gasket) or by no-hub couplings (shielded or unshielded). The 2018 GPC permits both methods, but the requirements differ:

Lead and oakum joints: The oakum is packed into the hub, and molten lead is poured and caulked. The code requires that the lead be poured in one continuous operation and that the joint be caulked to a uniform depth.

Gasket joints: A compression gasket is placed in the hub, and the spigot is pushed in. The gasket must be listed for the pipe size and service.

No-hub couplings: These use a stainless steel shield and clamp. The code requires that the coupling be tightened to the manufacturer’s torque specification. The 2018 GPC specifically requires that no-hub couplings in concealed locations be of the shielded type, not the unshielded (neoprene sleeve with clamps only) type.

Field point: No-hub couplings are the most common joint in modern DWV systems. The master plumber must ensure that the torque wrench is used, not a hand-tightened screwdriver. Overtightening can crack the pipe; undertightening causes leakage.

1.10 Joints for PEX and Other Crosslinked Polyethylene

PEX piping is joined by crimp rings, clamp rings, or expansion fittings. The 2018 GPC requires that all PEX fittings be listed for the specific PEX pipe and installed with the manufacturer’s required tooling.

Key code points:

Crimp rings must be checked with a go/no-go gauge after installation.

Expansion fittings must be installed with the proper expansion tool and allowed to contract fully before pressurization.

PEX cannot be joined with solvent cement or threaded fittings (except transition fittings listed for that purpose).

Exam trap: The code does not permit PEX to be used for gas piping unless specifically listed for that service. Standard plumbing PEX is not rated for gas.

1.11 Transition Joints (Dissimilar Materials)

The 2018 GPC requires that joints between dissimilar materials be made with approved transition fittings that account for differences in thermal expansion, corrosion potential, and pressure rating.

Common transitions:

Copper to galvanized steel: Use a dielectric union or dielectric nipple to prevent galvanic corrosion.

Plastic to metal: Use a threaded adapter with a transition gasket.

Cast iron to plastic: Use a shielded coupling with a rubber sleeve rated for the service.

The code prohibits the direct threading of plastic pipe into metal fittings without a listed transition fitting. This is a frequent code violation in water heater connections.

1.12 Pressure Testing Requirements

All joints must be tested after installation and before concealment. The 2018 GPC requires that the plumbing system be tested with water or air. The test pressure must be not less than 10 psi for water distribution and not less than a 10-foot head of water for drainage systems. The system must hold the test pressure for at least 15 minutes without leakage.

For gas piping, the 2018 GGC requires a pressure test of not less than 10 psi for systems operating at pressures above 0.5 psi, and not less than 3 psi for low-pressure systems. The test must be held for at least 15 minutes, and the master plumber must be present during the test.

Master-level responsibility: The master plumber is responsible for ensuring that all joints are accessible for testing before concealment. This requires coordination with other trades and a clear testing schedule.

1.13 Code Navigation — Where to Find It

Concept	Code Location (2018 GPC / GGC)
General joint requirements	GPC Chapter 3, Section 305 (general installation)
Solvent cement joints	GPC Chapter 7, Section 705 (sanitary drainage); Chapter 6, Section 605 (water distribution)
Threaded joints	GPC Section 605.2 (water); GGC Chapter 4, Section 404
Soldered and brazed joints	GPC Section 605.3 (water); Section 705.3 (drainage)
Mechanical joints	GPC Section 605.4; GGC Section 404.6
Flanged joints	GPC Section 605.5; GGC Section 404.7
Welded joints	GPC Section 605.6; GGC Section 404.8
Cast iron joints	GPC Section 705.4 (hub and spigot); Section 705.5 (no-hub)
PEX joints	GPC Section 605.7 (water distribution)
Transition fittings	GPC Section 605.8 (water); Section 705.6 (drainage)
Pressure testing	GPC Chapter 3, Section 312; GGC Chapter 4, Section 406
Lead-free solder requirement	GPC Section 605.3.1 (potable water)
Gas joint materials	GGC Chapter 4, Section 404.1 (prohibited joints)

1.14 Common Exam Traps and Field Realities

105.Soldered joints in gas piping: The GGC prohibits soldered joints for gas. Many candidates confuse plumbing and gas rules. Gas systems require threaded, flanged, or welded joints only.

106.Lead-free solder on potable water: The 2018 GPC requires lead-free solder for all potable water joints. The master plumber must verify the solder label, not just assume the crew used the correct material.

107.No-hub couplings in concealed locations: The code requires shielded couplings in concealed locations. Unshielded (band-only) couplings are permitted only in exposed locations.

108.Primer for PVC: The code requires primer for PVC solvent cement joints. A one-step cement without primer is not permitted unless the cement is specifically listed for that use.

109.Threaded joints in gas piping: The GGC requires that joint compound be applied to the male threads only and that it be resistant to LPG if the system carries LPG. Applying compound to the female threads is a violation.

110.Dielectric unions: The code requires dielectric separation between copper and galvanized steel. A brass nipple is not a dielectric fitting.

111.Pressure testing before concealment: The master plumber must ensure that all joints are tested before drywall or other concealment. Failure to do so results in a failed inspection and costly rework.

112.Manufacturer instructions: The code requires compliance with manufacturer installation instructions. If the manufacturer requires a specific cure time for solvent cement, the master plumber must allow that time before pressure testing.

1.15 The Master Plumber’s Supervisory Duty

As a master plumber, you are the responsible licensed professional on the project. The code holds you accountable for the work of your journeymen and apprentices. This means:

You must verify that the correct joining method is used for each material and service.

You must ensure that all installers are trained and competent in the specific joining technique.

You must document the materials used (solder, cement, gaskets) and retain certificates of compliance where required.

You must schedule and witness all required pressure tests.

In a legal context, the code’s requirement that joints be made “in accordance with the manufacturer’s instructions” places the burden on you to know those instructions. Ignorance is not a defense in an inspection dispute or a liability claim.

Summary

Pipe cutting and joining is not a simple trade skill—it is a code-regulated engineering decision. The 2018 Georgia Plumbing Code and 2018 Georgia Gas Code establish specific requirements for each material and service, and the master plumber must know not only what is permitted but also why it is permitted. Mastery of this chapter requires understanding the interaction between material properties, joint design, and system service conditions. On the exam, expect questions that test your ability to distinguish between permitted and prohibited joints, to identify the correct code section for a given situation, and to apply the pressure testing requirements correctly.

Pipe Cutting and Joining