4.Identify the approved materials for each plumbing system type (water supply, drainage, vent, and fuel gas) under the 2018 IPC and IFGC.
5.Apply the code’s hierarchy for material selection, including the prohibition of specific materials in certain applications.
6.Navigate the code’s tables and chapters to verify material standards, ratings, and temperature/pressure limitations.
7.Recognize the Maryland-specific amendments and the role of the Authority Having Jurisdiction (AHJ) in material approvals.
8.Evaluate field conditions—such as soil corrosion, thermal expansion, and chemical exposure—that dictate material choice beyond the minimum code requirement.
9.Identify common exam traps involving material mixing, dielectric connections, and the difference between "shall be" and "approved" language.
1.1 The Legal Framework: Code Hierarchy and Approvals
As a master plumber, you are responsible for ensuring that all materials are approved—a term the code defines as acceptable to the AHJ. The 2018 IPC establishes minimum standards, but Maryland regulations and local amendments may impose stricter requirements. The code’s Chapter 3 (General Regulations) and Chapter 5 (Water Heaters) contain the overarching approval criteria, while specific material standards are referenced in the individual system chapters.
Key principle: Any material not listed in the code must be submitted for approval with test data. The burden of proof is on the installer, not the inspector. For the exam, remember that the code references ASTM, ANSI, ASME, and NSF standards—these are the only acceptable benchmarks.
1.2 Water Supply and Distribution Materials (IPC Chapter 6)
1.2.1 Permitted Materials
The 2018 IPC Table 605.4 (Water Service Pipe and Water Distribution Pipe) is the master reference. It lists materials by standard, including:
Copper tube (Types K, L, M) per ASTM B88, and copper water tube per ASTM B88M.
CPVC (chlorinated polyvinyl chloride) per ASTM D2846, rated for hot and cold water.
PEX (cross-linked polyethylene) per ASTM F876/F877, with a critical distinction between PEX-A, PEX-B, and PEX-C—the code does not prefer one, but the standard must be met.
PE-RT (polyethylene of raised temperature resistance) per ASTM F2769.
Galvanized steel pipe per ASTM A53, but only for cold water in most jurisdictions; Maryland often restricts its use for hot water due to corrosion.
Stainless steel (Type 304/316) per ASTM A312 for specialized applications.
Exam trap: The code does not permit PVC (polyvinyl chloride) for hot or cold water supply. PVC is only for drainage. A common question will ask which material is acceptable for a 160°F water supply—answer: CPVC or PEX, not PVC.
1.2.2 Temperature and Pressure Ratings
Every material has a maximum working pressure and temperature rating. For example:
PEX: 100 psi at 180°F, but 160 psi at 73°F—the rating is derated with temperature.
CPVC: 100 psi at 180°F (per ASTM D2846).
Copper: pressure-rated based on wall thickness; Type M is thinner than Type L, so it is not permitted for underground service in some jurisdictions.
The code requires that the system pressure (including surge) not exceed the lowest-rated component. A master plumber must calculate static head, pump pressure, and thermal expansion pressure (see IPC 607 for thermal expansion control).
1.2.3 Dielectric Connections and Material Mixing
Where dissimilar metals are joined (e.g., copper to galvanized steel), the code requires a dielectric fitting or a dielectric union to prevent galvanic corrosion. This is a frequent field inspection point. The exam will test your knowledge of where this is required—at the water heater connections, at the main supply, and at any transition point.
Maryland note: The State Plumbing Code may require a minimum of 18 inches of copper or brass pipe at the water heater outlet before transitioning to PEX—this is a common local amendment, not in the IPC.
1.3 Drainage, Waste, and Vent Materials (IPC Chapter 7)
1.3.1 Permitted Materials
Table 702.1 (Drainage and Vent Pipe) is the controlling table. Approved materials include:
Cast iron (hub and spigot, no-hub) per ASTM A74 or CISPI 301.
PVC (DWV) per ASTM D2665—the most common residential material.
ABS (acrylonitrile butadiene styrene) per ASTM F628, but only where permitted by the AHJ; Maryland typically allows ABS but requires a specific solvent cement.
Copper (DWV) per ASTM B306, used in high-end or corrosive environments.
Galvanized steel—permitted for drainage in some industrial settings, but rarely used today.
Critical distinction:PVC and ABS cannot be mixed in the same drainage system unless a listed transition coupling is used. The code is explicit: the same thermoplastic material must be used throughout the system, or an approved mechanical joint must bridge the transition.
1.3.2 Prohibited Materials
The code prohibits concrete, clay, and asbestos-cement pipe for new drainage systems (though existing systems may remain). It also prohibits lead in any new potable water or drainage system—a point reinforced by Maryland’s lead ban.
1.3.3 Fittings and Joints
Fittings must match the pipe material and standard. For example:
PVC fittings per ASTM D3311 (drainage pattern) or D2466 (pressure).
No-hub cast iron couplings per CISPI 310, with stainless steel shields and bands.
Exam trap: A question may ask whether a pressure-rated PVC fitting (Schedule 40) can be used on a DWV system. The answer is yes—pressure-rated fittings are stronger and acceptable—but DWV fittings cannot be used on a pressure system.
1.4 Fuel Gas Piping Materials (IFGC Chapter 4)
1.4.1 Approved Materials
The 2018 IFGC Table 403.1.1 lists acceptable gas piping materials:
Black steel (ASTM A53) — the standard for rigid gas piping.
Galvanized steel — permitted only above ground and where condensation is not expected; the zinc coating can flake and clog orifices.
Copper — permitted for gas, but not for systems carrying gas with more than 0.3 grains of hydrogen sulfide per 100 cubic feet (corrosive to copper). Maryland follows this with strict limits.
CSST (corrugated stainless steel tubing) per ANSI LC-1 — must be installed per the manufacturer’s instructions and bonded per NFPA 70.
Polyethylene (PE) — for underground service only, per ASTM D2513.
1.4.2 Prohibited Materials
The IFGC prohibits aluminum (in some jurisdictions) and PVC for gas piping. It also prohibits reused pipe unless it is clean and free of scale. A master plumber must verify that pipe has not been previously used for other fluids.
1.4.3 Sizing and Pressure
Gas pipe sizing is not a materials question per se, but the pressure drop calculation (IFGC Chapter 4, Section 402) determines the required diameter. The code uses the longest length method and tables for natural gas (0.60 specific gravity) and propane (1.50 specific gravity). The exam will test your ability to select the correct table and apply the 0.5-inch water column drop for low-pressure systems.
1.5 Maryland-Specific Amendments and AHJ Authority
Maryland adopts the IPC and IFGC with state amendments. Key points for the exam:
The Maryland State Board of Plumbing may approve materials not listed in the code if they meet equivalent standards.
Backflow prevention devices must be ASSE or CSA certified—this is a materials requirement, not just an installation one.
Lead-free requirements: All pipe, fittings, and solder must meet the federal Safe Drinking Water Act definition (≤0.25% lead in wetted surfaces). The code references this in Chapter 6.
Field point: As the master plumber, you are the responsible licensed person. If you install a material that is not code-listed, you bear the liability—not the manufacturer. Always request a product approval letter from the AHJ before installation.
1.6 Corrosion, Protection, and Durability
1.6.1 Soil and Environmental Conditions
IPC Chapter 3 (Section 305) requires that underground metal pipe be protected against corrosion. This means:
Galvanic corrosion — use dielectric unions at dissimilar metal junctions.
Soil corrosion — wrap cast iron or steel in polyethylene encasement (ASTM A674) in corrosive soils.
Chemical exposure — do not run metal pipe through concrete or masonry without a sleeve or protective coating.
1.6.2 Thermal Expansion
All materials expand with temperature. The code requires expansion loops or offsets for long runs of PEX and CPVC (IPC 606.3). For copper, the code allows rigid connections but requires a thermal expansion tank on closed water systems (IPC 607.3). The exam will test your knowledge of when the tank is required—when a check valve, backflow preventer, or pressure-reducing valve is present.
1.7 Identification and Marking
Every pipe and fitting must be marked with the manufacturer’s name, the standard designation, and the pressure rating. The code requires that markings be visible after installation—a common inspection failure is when pipes are painted over or labels are removed.
Exam trap: A question may show a pipe with a label that is not legible. The correct answer is that the pipe must be removed or the marking restored—not simply "acceptable if the inspector knows the brand."
1.8 Code Navigation: Where to Find It
Topic
Code Location
General approval criteria
IPC Chapter 3, Section 301.2
Water supply materials table
IPC Table 605.4
Thermal expansion control
IPC Section 607.3
Dielectric connections
IPC Section 605.6
Drainage pipe materials table
IPC Table 702.1
DWV fittings and joints
IPC Section 705
Gas pipe materials table
IFGC Table 403.1.1
Gas pipe sizing tables
IFGC Tables 402.4 (natural gas) and 402.5 (propane)
CSST bonding
IFGC Section 310.1 (and NFPA 70)
Lead-free requirements
IPC Section 601.2 (and federal law)
Maryland amendments
Maryland State Plumbing Code regulations (separate document)
OSHA excavation safety
29 CFR 1926 Subpart P (for trenching)
1.9 Practical Field Points for the Master Plumber
92.Verify material certifications before ordering. The code accepts only listed standards. A "look-alike" product without the ASTM stamp is not code-compliant, regardless of performance.
93.Check the AHJ’s approved materials list. Some Maryland counties restrict PEX or require expansion fittings at every manifold. Know your jurisdiction.
94.Document material substitutions. If you substitute a material, you must obtain written approval before inspection—verbal approvals are not defensible.
95.Train your crew on material handling. PEX must be protected from UV light; CPVC requires special solvent cement; cast iron no-hub couplings must be torqued properly. Material failure is often an installation error, not a product defect.
96.Understand OSHA interaction. Excavation for underground pipe is governed by 29 CFR 1926 Subpart P. As the master plumber, you are responsible for trench safety—even if you are not the general contractor.
1.10 Common Exam Traps
PVC vs. CPVC: PVC is drainage-only; CPVC is for hot water. The names are similar—the exam will test this.
ABS vs. PVC: They cannot be glued together. A transition coupling is required.
Copper Type M vs. L: Type M is thinner and not permitted for underground service in many jurisdictions. The code table lists both, but the AHJ may restrict.
Galvanized pipe for gas: Permitted above ground, but not where condensation is likely. The exam may ask about a basement run with a long horizontal section.
PEX and UV exposure: PEX cannot be stored in sunlight for extended periods. The code requires protection from UV if installed outdoors.
"Approved" vs. "Listed": An approved material meets the AHJ’s criteria; a listed material appears on a recognized list. The exam will use both terms—know the difference.
Summary
Material selection is the foundation of code compliance. The 2018 IPC and IFGC provide tables that list acceptable standards, but the master plumber must interpret those tables in the context of temperature, pressure, soil conditions, and Maryland amendments. In an open-book exam, your ability to navigate to the correct table quickly is as important as your knowledge of the material itself. Practice locating Table 605.4, Table 702.1, and IFGC Table 403.1.1 until you can find them in seconds. Remember: the code is a minimum standard—your professional judgment must exceed it where conditions demand.
