3.1 Approved Plumbing Materials, Pipes & Jointing

3.1 Approved Plumbing Materials, Pipes & Jointing

Quick Answer: Approved plumbing materials and joining methods are dictated by IPC Chapters 3, 6, and 7, as well as COMAR 09.20. Potable water piping must be NSF 61 certified. DWV plastics require specific solvent cements (ASTM D2564 for PVC with purple primer ASTM F656; ASTM D2235 for ABS). Copper water tubing is categorized as Type K (thickest), Type L (medium), and Type M (thinnest, interior above-ground only), joined using lead-free solder (<0.2% lead).

Selection of code-compliant piping materials and proper joint assembly are foundational to plumbing safety, preventing structural leaks, chemical contamination, and premature system failure.

Material Standards & Certification Markings

All materials, fixtures, and pipe fittings installed in potable water, drainage, or venting systems must bear the mark of an accredited third-party testing agency (such as NSF, UL, CSA, or IAPMO) certifying compliance with applicable ASTM, ANSI, or ASME standards.

• Potable Water Safety (NSF/ANSI 61 & 14): Any pipe, fitting, valve, or solder in contact with drinking water must meet NSF/ANSI 61 for health effects and NSF 14 for structural performance.
• Lead-Free Standard: Per the Safe Drinking Water Act and IPC Section 605, pipes, pipe fittings, plumbing fittings, and fixtures conveying potable water must have a weighted average lead content of no more than 0.25%, while flux and solder must contain no more than 0.2% lead.

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Drainage, Waste & Vent (DWV) Piping Materials

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Potable Water Distribution Piping Materials

Potable water supply systems require materials that withstand continuous hydraulic pressure (typically 40–80 psi) and temperature variations.

Copper Tubing (ASTM B88)

Copper tubing is manufactured in three standardized wall thicknesses for plumbing applications. Outside diameters (OD) remain identical across all three types for a given nominal size, but wall thickness varies significantly:

1. Type K (Green Color Code): Heavy wall thickness. Approved for underground water service lines, commercial mains, and severe industrial applications. Available in hard temper (straight lengths) and soft temper (coils).
2. Type L (Blue Color Code): Medium wall thickness. The standard choice for interior water distribution branches and commercial plumbing. Approved for both interior above-ground lines and underground water services.
3. Type M (Red Color Code): Light/thin wall thickness. The IPC lists Type M among the approved water service and water distribution materials (Tables 605.3 and 605.4). The restriction of underground work to Type K or L is a Uniform Plumbing Code rule and a local utility requirement (WSSC among them), not an IPC prohibition - answer from the IPC unless the question names the local code.

Cross-Linked Polyethylene (PEX - ASTM F876/F877)

PEX is a flexible plastic piping material widely used for hot and cold potable water lines:

• Temperature & Pressure Ratings: 160 psi at 73°F; 100 psi at 180°F; 80 psi at 200°F.
• Types: PEX-a (Engels method, highest flexibility, memory effect), PEX-b (Silane method), PEX-c (Electron beam method).
• Joining Systems: ASTM F1807 (metal/poly crimp rings with PEX crimp tool), ASTM F1960 (cold-expansion fittings using PEX-a expansion rings), ASTM F2080 (expansion with reinforcement collar).
• Code Limits: Must be kept at least 6 inches away from gas appliance water heater vents, protected from UV light exposure, and sleeved when passing through concrete slabs.

Chlorinated Polyvinyl Chloride (CPVC - ASTM D2846 / ASTM F441)

Rigid plastic piping formulated specifically for hot and cold potable water (rated for 100 psi at 180°F). Joined using CPVC primer and orange CPVC solvent cement (ASTM F493).

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Joining Methods, Mechanics & Code Rules

Proper joint assembly is essential to preserve system pressure and prevent environmental leaks.

Prohibited Pipe Joining Practices

IPC Chapter 3 and Chapter 7 strictly prohibit specific pipe joining methods due to high failure rates and contamination risks:

1. Direct PVC-to-ABS Solvent Welding: Joining PVC to ABS with solvent cement is prohibited except for one single joint between ABS and PVC pipe at the end of the building drainage pipe and the beginning of the building sewer, made with a solvent cement complying with ASTM D3138 (IPC 707.1 item 5 and 705.16.4). The two plastics have different chemical compositions and expansion rates. Transitions between PVC and ABS must be made using approved mechanical transition couplings or threaded transition adapters.
2. Saddle Tees & Saddle Valves: Saddle fittings that clamp onto existing pipes and pierce the wall are PROHIBITED on both DWV and potable water systems. They restrict flow, accumulate debris, and leak frequently.
3. Unapproved Dissimilar Metal Connections (Galvanic Action): Direct connection of copper tubing to galvanized steel pipe without a dielectric union, brass nipple, or approved insulating fitting is prohibited. Galvanic corrosion rapidly destroys the steel pipe threads.
4. Drilled/Tapped Joints on DWV: Drilling and tapping a drainage pipe to connect a branch line is prohibited.

Exam Trap: A common exam trick involves asking whether purple primer is required when solvent welding ABS pipe. Remember: ABS requires ABS cement ONLY (ASTM D2235). Purple primer is designed for PVC and CPVC—applying primer to ABS will soften and damage the resin matrix!

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Material Temperature & Pressure Comparison