Repipe Your Home: Should You Choose PEX-A or PEX-B? An Honest Comparison.

Pex A or Pex B?

If you're considering repiping your home, you're probably facing some tough decisions—like whether to choose PEX-A or PEX-B piping. You might also be wondering how these modern materials stack up against old-school copper. Which lasts longer? Which performs better? What could go wrong?

This comprehensive guide breaks down everything you need to know about PEX-A vs. PEX-B—so you can confidently move forward with your repipe project and avoid costly mistakes.

What Is PEX and Why It's Popular for Repiping

PEX stands for cross-linked polyethylene, a type of flexible plastic piping that’s revolutionized modern plumbing. First introduced in the U.S. market in the 1980s, PEX has become the go-to choice for residential repipes because it:

• Doesn’t corrode like copper

• Is more affordable than copper

• Handles freezing better

• Installs faster with fewer fittings

PEX comes in several variations, but the most common types used in repipes are PEX-A and PEX-B. Both are great—but there are key differences you need to know before choosing one over the other.

PEX-A vs. PEX-B: What’s the Difference?

While both PEX-A and PEX-B are forms of cross-linked polyethylene, the difference lies in how the plastic is cross-linked and how the tubing behaves during installation and long-term use.

Pex A Vs. Pex B

Lifespan and Durability

Both PEX-A and PEX-B have long lifespans—usually 40 to 50 years or more when installed correctly and protected from UV light and excessive heat.

However:

• PEX-A’s flexibility means fewer stress points and fewer chances of long-term cracking.

• PEX-B is stiffer and may be more prone to stress in tight bends, but it actually has a slightly higher burst pressure rating in lab testing.

That means PEX-B might hold up better under extreme water pressure, while PEX-A is more resilient in freeze-thaw environments.

Pex Performance Compared to Copper

Here's where things get interesting. Copper has been a gold standard in plumbing for decades, but it’s not without flaws:

Pex Vs. Copper

PEX (both A and B) generally outperforms copper in cold climates and is more cost-effective. However, copper still holds an edge in certain high-heat, high-pressure scenarios and is often preferred by traditionalists or in homes with exposed plumbing. For this reason you will still see copper for at least 18" coming off of your gas water heater before making the transition to pex.

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Common Issues With PEX-A and PEX-B

Every piping material has pros and cons. Here's what can go wrong with PEX:

PEX-A

• Requires expansion fittings that can be confusing and costly for DIYers

• Higher risk of damage from UV light (must not be exposed)

  
  

PEX-B

• More prone to kinking (and can’t be repaired like PEX-A)

• Slightly more brittle over time in cold climates

• Requires more elbow fittings in tight spaces due to reduced flexibility

But here’s the good news: most issues with PEX piping come from poor installation, not the material itself.

PEX-A vs. PEX-B: The Water Pressure Difference

When choosing between PEX-A and PEX-B for repiping your home, one of the most important differences is how each type handles fittings—and how those fittings affect your water pressure.

PEX-A: Full Flow with Expansion Fittings

PEX-A uses an expansion fitting system. That means we slightly expand the pipe and insert a fitting, allowing the pipe to shrink back around it and create a secure seal. Because the pipe expands before the fitting goes in, the internal diameter stays wide open, maintaining nearly full water flow through every connection point.

In simple terms: the water isn’t getting squeezed or forced through narrow points—so you get strong, steady pressure, even when multiple fixtures are running. This is especially important in larger homes with long pipe runs, multiple bathrooms, and high water demand.

PEX-B: Choked Flow with Crimp Fittings

PEX-B uses crimp or clamp-style fittings, which pinch a ring around the outside of the pipe to hold it onto the fitting. Unlike PEX-A, the pipe doesn’t expand—it hugs tightly around a smaller-diameter fitting that sits inside the pipe.

That means at every connection point, the water has to push through a narrower opening, slightly reducing flow. In small homes, you might never notice. But in larger homes with lots of plumbing fixtures or long distances between bathrooms and the water heater, that pressure drop can add up—leading to frustratingly weak showers or slow-filling tubs.

Pex A - Expansion / Pex B Contraction

Installation Differences Between Pex A and Pex B

While both PEX-A and PEX-B are solid choices for repiping, how they’re installed—and how that affects your water flow—makes a big difference.

PEX-A: Expansion Fittings and Full-Flow Advantage

PEX-A is installed using a unique expansion fitting system. Here’s how it works:An installer uses a tool to stretch open the end of the pipe and a plastic ring. Then, the fitting is inserted while the pipe is still expanded. Over the next few seconds, the PEX-A naturally shrinks back down and creates a super-tight seal around the fitting.

But here's the real benefit:The fitting goes inside the pipe, but because the pipe was expanded first, the diameter of the flow path stays nearly the same. That means the water can move through the system without getting choked down or restricted.

This is especially helpful in homes with long runs of pipe or when multiple fixtures are used at once (like showers, laundry, and faucets all going at the same time).

PEX-B: Crimp Fittings and Flow Restrictions

PEX-B uses crimp or clamp-style fittings, which are simpler to install and don’t require an expansion tool. The downside?The fitting stays the same size, and the pipe wraps tightly around it. That means the inner diameter of the pipe shrinks at every connection point.

So instead of smooth sailing, the water now has to squeeze through a smaller space every time it passes a fitting—causing pressure drops and slightly reduced flow.

This isn’t usually a deal-breaker, especially for smaller homes or simple layouts. But in larger homes or homes with high water demands, that cumulative restriction can make a difference—especially during peak usage.

Is Pex A or Pex B Better In Climates Where Pipes Can Freeze?

This is where PEX-A shines.

• PEX-A can expand up to 3x its diameter and then return to shape—ideal in freezing climates.

• PEX-B is more rigid and can crack under freeze conditions, though it still performs better than copper.

If your area sees hard freezes, PEX-A is the better choice.

10. When to Choose PEX-A Over PEX-B (And Vice Versa)

Choose PEX-A if:

• You live in a freeze-prone climate

• You want the most flexible, adaptable material

• You’re working with lots of tight spaces

• You’re hiring a professional who uses expansion fittings

Choose PEX-B if:

• You want to save money and try to DIY

• Your home is in a mild climate

• Your installer prefers crimp/clamp fittings

• You value long-term strength and pressure rating

Pex A Expansion Installation

Repipe Myths: What You Shouldn't Worry About

• PEX doesn’t leach dangerous chemicals long-term—initial flushing resolves this concern.

• Rodents don’t prefer PEX over any other piping—they’ll chew almost anything.

• PEX isn’t “cheap” plumbing—it’s what most luxury home builders now use.

  
  

Verdict: Which PEX Is Best for Repiping Your Home?

Here’s the bottom line:

• PEX-A is the gold standard for flexibility and freeze protection.

• PEX-B is the smart budget choice for homes in warmer climates or simpler layouts.

• Both outperform copper in freeze resistance, ease of installation, and cost.

If you're working with a licensed plumber, ask which type they specialize in and why. A skilled installer can make either option a great long-term choice.

Frequently Asked Questions About Pex Installations

Q: How long does a PEX repipe take?A: Most homes can be fully repiped in 1–5 days.

Q: Can PEX be used for both hot and cold water?A: Yes, both PEX-A and PEX-B are rated for 180°F+ water.

Q: Can PEX be buried underground?A: Yes, but it should be sleeved or protected to prevent damage.

Q: Does PEX increase home value?A: Yes—modern plumbing upgrades often increase resale value and reduce inspection red flags.

Choosing between PEX-A and PEX-B comes down to your climate, budget, and installer preferences.

Don’t let the wrong choice lead to regret down the line. Take the time to understand the differences, ask smart questions, and make an informed decision that will protect your home for decades.

Looking to repipe your home in Pittsburgh? Give Revelation Plumbing a call, we can help you choose the best material for your needs—and install it right the first time. 412-518-7170

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