PEX A vs. PEX B

PEX A vs. PEX B: Pros, Cons, and Interior Diameter Differences for Home Repiping

When repiping your home, two of the most common options are PEX A and PEX B. Both are types of cross-linked polyethylene pipe, but they differ in manufacturing methods, performance, flexibility—and importantly—interior diameter.

PEX-A (Engel Method / Peroxide Cross-linking)

 Pros:

• Superior Flexibility: PEX-A is the most flexible, ideal for retrofits and tight spaces.
• Cold Expansion Fittings: Uses expansion fittings (e.g., Uponor), which allow the pipe to expand over the fitting and then shrink tight, creating a highly secure seal.
• Freeze Resistance: Less likely to crack if frozen due to flexibility.
• Shape Memory: Recovers from kinks when heat is applied—no need to cut out damaged sections.
• Larger Interior Diameter: Expansion fittings fit inside the pipe, preserving the full bore. This gives PEX-A slightly better flow capacity compared to PEX-B with crimp-style fittings.

 Cons:

• Higher Cost: PEX-A is typically 25–35% more expensive than PEX-B.
• Less Widely Available: Not as common in hardware stores.
• Slightly Lower Burst Pressure: Though still more than adequate for residential use.

PEX-B (Silane Method / Moisture Cure)

 Pros:

• Cost-Effective: Significantly cheaper than PEX-A, great for large-scale repiping.
• Stiffer Structure: Holds straight runs better; ideal for slab or open-wall installations.
• High Burst Strength: Excellent resistance to pressure, especially at higher temps.
• Widespread Availability: Common in most hardware stores.

 Cons:

• Less Flexible: More difficult to route through tight corners or around obstructions.
• Kinks Are Permanent: Damaged sections typically need to be cut and replaced.
• Crimp or Clamp Fittings Only: These fit around the pipe, slightly reducing interior diameter and thus reducing flow marginally.
• Reduced Flow Capacity: Because the fittings go over the pipe, PEX-B typically has a smaller effective interior diameter than PEX-A of the same nominal size.

 Interior Diameter Differences

Note: Differences depend on the brand and fitting type, but in general, PEX-A allows for slightly better flow rates at a given size due to larger interior diameters when using expansion fittings.

 Summary Table

 Which One Is Best for Your Home?

• Choose PEX-A if:
  • You want the most flexible, freeze-resistant option.
  • You’re using a system like Uponor with expansion fittings.
  • Slightly better flow performance is a priority.
• Choose PEX-B if:
  • You’re on a tighter budget.
  • You’re working with straight runs or new construction.
  • Your contractor uses crimp-style tools and fittings.