Whether you’re installing new water lines or considering a repipe, you’ve likely come across PEX A and PEX B. Both are types of cross-linked polyethylene (PEX), a flexible yet durable plastic that’s been a game-changer for modern plumbing. Yet the question persists: which version is superior in terms of flexibility, ease of connection, and burst pressure?

Below, we’ll walk you through the basics of PEX A and PEX B, including the differences in how they’re manufactured and installed. We’ll also share the results from our “blast chamber” pressure tests, where we push these pipes to their limits to see how much pressure they can truly handle. By the end, you’ll have a clearer sense of which type might be best for your next plumbing project.

Understanding PEX A and PEX B

What Does PEX Stand For?

PEX is short for “cross-linked polyethylene,” referring to the molecular structure that makes the plastic more robust and heat-resistant. The “A” and “B” designations reflect the manufacturing methods used to create these cross-links, not necessarily a measure of quality.

PEX A

• Expansion Method: Often paired with an expansion-style fitting system (like Uponor).
• Greater Flexibility: PEX A can handle tighter bends and expand a bit more to resist freeze damage.
• Thermal Memory: If you accidentally kink it, you can often revert the pipe to its original shape with a heat gun.

PEX B

• Crimp or Clamp Method: Commonly installed using copper crimp rings or stainless steel clamps.
• Stiffer Material: Not as flexible as PEX A and can’t always revert to shape if kinked.
• Wider Availability: Often found in hardware stores, typically at a lower cost than PEX A.

Installation Key Points

PEX A Installation

1. Expansion Rings: You slide an expansion ring onto the pipe and use an expansion tool to stretch both ring and pipe.
2. Fitting Insertion: After the expansion, you insert the fitting and the pipe/ring assembly contracts back around it.
3. Natural “Memory”: Over time, the pipe continuously squeezes around the fitting, forming a tight seal without clamps or crimps.

PEX B Installation

1. Cut and Deburr: Ensure a clean, square cut.
2. Slide on Crimp Ring: Place the ring about 1/8 inch from the pipe’s end.
3. Insert Fitting: Push the fitting into the pipe fully.
4. Crimp or Clamp: Use the specific tool for your chosen ring system. Verify with a go/no-go gauge to ensure proper tension.

Pressure Test Setup

To see just how much pressure these pipes can handle, we used our “blast chamber”—a secure container where we can safely pressurize piping beyond typical household levels. Each assembly featured:

• One Section of PEX: Either A or B.
• Appropriate Fittings: Expansion fittings for PEX A, crimp fittings for PEX B.
• High-Pressure Water: Fed into the pipe until a burst occurred or maxed out our testing capabilities.

We performed two tests per type (two PEX A samples and two PEX B samples) to observe consistency. We also confirmed there were no leaks at the fittings prior to ramping up the pressure.

The “Blast Chamber” Results

1. PEX B (Test 1)

   • Burst Pressure: 1,151 psi
   • Failure Point: Pipe wall burst, not at the fitting.

2. PEX B (Test 2)

   • Burst Pressure: 1,053 psi
   • Similar to Test 1, the break occurred in the pipe section, not the connection.

3. PEX A (Test 1)

   • Burst Pressure: 959 psi
   • Rupture Location: Mid-pipe area.

4. PEX A (Test 2)

   • Burst Pressure: 910 psi
   • Same trend: the pipe, rather than the expansion joint, gave way.

What the Numbers Mean

Even though PEX B slightly outperformed PEX A in terms of raw burst pressure in this particular test, both types surpassed what’s required for typical household pressures. Most homes sit at 40 to 80 psi, far below even the lowest failure point we recorded.

PEX A still has advantages in cold climates (due to expansion) and in tight bends or repair scenarios (since heat guns can fix kinks). PEX B, while less flexible, is often cheaper and perfectly sufficient for many residential water lines, thanks to its robust clamp/crimp system.

Should Burst Pressure Be Your Only Concern?

Burst pressure tells you how a pipe performs under extreme stress—useful info, but not the sole factor in choosing a piping system. Consider:

1. Local Building Codes: Some areas prefer or mandate one type over the other.
2. Ease of Installation: Expansion fittings vs. crimp fittings can affect speed and accessibility.
3. Tools Needed: Expansion tools (PEX A) vs. crimp/clamp tools (PEX B) may influence your budget.
4. Freeze Resistance: PEX A can tolerate more freeze-thaw cycles thanks to its greater elasticity.
5. Cost: PEX B is often cheaper in material costs, which may matter for large-scale projects.

Conclusion

Both PEX A and PEX B can handle pressures far beyond what most homes will ever see. Yes, in our “blast chamber” tests, PEX B maintained a slightly higher burst pressure. But PEX A’s flexibility and heat-repairable kink feature are huge selling points, especially in colder regions.

Ultimately, the right choice depends on your project’s specific needs—cost, local code requirements, and personal installation preferences. If you value higher expansion and the possibility of kink fixes, opt for PEX A. If you prefer a simpler crimp system and a bit more budget-friendly approach, PEX B is a great option.