If you’re weighing PEX-A against PEX-B for a repipe, here’s the short answer: neither letter is a quality grade. The Plastics Pipe Institute (PPI) states plainly that the letter designations are not tied to any rating system, and that PEX made by any approved method has to meet the same qualification and performance requirements under ASTM F876, AWWA C904 and CSA B137.5.
So the real question isn’t “which letter wins.” It’s which joining system your house needs, and whether the tubing on the truck is approved for it. That answer is already printed on the pipe.
We’ve been running plumbing in Anne Arundel County since 1952, which means Abend Services has watched every generation of pipe material come and go here, including the polybutylene pipe replacement in Maryland homes built 1978 to 1995 work that still lands on our schedule most weeks. That history is why we start with the print line instead of the letter.
Below is what changed in 2025 and 2026, what the current code actually requires in this county, and the four things a licensed plumber reads before picking a pipe.
The letters describe how the plastic was crosslinked, nothing more.
ASTM F876 sets a minimum degree of crosslinking of 65% for all of them. And all PEX for hot and cold water distribution in North America is copper tube size (CTS), SDR 9, which means the dimensions match exactly.
| What you’re comparing | PEX-A | PEX-B |
| Crosslinking method | Peroxide, during extrusion | Silane, after extrusion |
| Outside diameter, 1/2 inch | 0.625 in | 0.625 in |
| Wall thickness, 1/2 inch | 0.075 in | 0.075 in |
| Inside diameter, 1/2 inch | 0.475 in | 0.475 in |
| Minimum crosslink, ASTM F876 | 65% | 65% |
| Pressure rating at 73F | 160 psi minimum | 160 psi minimum |
| Pressure rating at 180F | 100 psi minimum | 100 psi minimum |
| Free bend radius | No tighter than 6x actual OD | No tighter than 6x actual OD |
| Kink repair | Often reformable per manufacturer instructions | Damaged section cut out, coupling added |
| Usual fitting association | Cold expansion, ASTM F1960 | Crimp, clamp, press, push-fit |
Source for dimensions and ratings: PPI PEX Plumbing Distribution Systems Design and Installation Guide, Third Edition, Chapter 3 and Table 3.1, published April 2026.
Notice how much of that table is identical. That’s the point most comparison articles skip.
PPI released the third edition of its PEX design guide in April 2026. It’s the first full rewrite since 2013, runs 156 pages, was prepared by Home Innovation Research Labs with support from IAPMO and ICC, and it’s a free download.
Lance MacNevin, P.Eng., Senior Director of Engineering for PPI’s Building & Construction Division, explained the rewrite this way in phcppros (May 2026):
Since the second edition more than ten years ago, “many aspects of PEX plumbing systems have evolved.”
He also noted that PEX is now the most common hot and cold water distribution material in residential plumbing. Most pages competing for this topic were written before that rewrite existed.
ASTM F876 requires every length of PEX to carry a print line every 5 feet or less. That print line lists the size and SDR, the manufacturer, a production code, the PEX material designation code, the standards it meets, the pressure ratings, the certifier’s mark, and, critically, the standard designation of the fitting systems the tubing maker approves for that tubing (for example F1807 or F1960).
That’s why we run what we call the Abend Print-Line Check before quoting a repipe. Four things, read off the tubing and off the house:
Nothing in that list is “pick the premium letter.” Because there isn’t one.
This is the section that decides the job. PPI’s third edition lists these joining systems, and all of them are rated for 100 psi cold and hot water service up to and including 180F.
| Standard | What it is | Fitting materials |
| ASTM F1807 | Metal insert fitting with copper crimp ring or stainless clamp | Copper, stainless, lead-free brass or bronze |
| ASTM F2159 | Plastic insert fitting with copper crimp ring or stainless clamp | Sulfone polymer |
| ASTM F2098 | Stainless clamp used in place of a copper crimp ring | Stainless steel |
| ASTM F1960 | Cold expansion with a PEX reinforcing ring | Lead-free brass, stainless, polymer |
| ASTM F2080 | Cold expansion with a metal compression sleeve | Lead-free brass |
| ASTM F3347 / F3348 | Press insert fittings with factory-assembled stainless press sleeve | Lead-free bronze, polymer |
| ASSE 1061 | Push-fit | Lead-free brass or polymer |
Then comes the sentence we’d put on a poster if we could. From PPI’s guide, Chapter 5:
“Not all fittings are compatible with all PEX tubing.”
PPI’s instruction is to consult the tubing manufacturer for acceptable joining methods, or read the tubing markings.
Mixing components across brands, even when the parts look identical, is how leaks get built into walls. PPI warns against it, and the 2021 IPC requires installation per manufacturer instructions.
Yes, and more than the letter does. Insert-style fittings (F1807, F2159) sit inside the tube, so the opening at that joint is narrower than the tube’s inside diameter. Cold expansion fittings go into an expanded tube end, so more of the bore is preserved.
Across a whole house with dozens of joints, fewer and larger-bore connections mean less pressure drop. We don’t publish a percentage on that, because manufacturer bore tables vary by size and brand, and PPI directs readers to the system manufacturer for friction loss numbers. If your pressure already feels weak, it’s usually worth ruling out the low water pressure causes most homeowners overlook before assuming the pipe material is the problem.
Here’s where PEX-A’s thermal memory shows up on a job site.
Uponor, a PEX-A manufacturer, publishes in its customer FAQ that because of thermal memory you can “repair a kink with a shot of heat from a heat gun”, and states this is only possible with PEX-A. Kinks in PEX-B or PEX-C, per Uponor, cannot be repaired that way. MrPEX publishes a similar method for its PEX-A product.
PPI’s guide is stricter than either manufacturer: don’t use tubing that’s been crushed or kinked, follow the manufacturer’s instructions for damaged tubing, and note that approved fittings may be used to repair damaged distribution lines.
What this means for you, in plain terms: with PEX-A, a kink during installation can often be reformed under the manufacturer’s instructions. With PEX-B, that section gets cut out and a coupling goes in, which means one more joint sitting inside your wall. That’s a question to ask your plumber about what they carry and how they handle it. It is not a reason to buy a heat gun.
PEX as a material class is freeze-break resistant for three documented reasons, all from PPI’s Chapter 3:
Research cited in PPI TR-52, as reported by Plumbing & Mechanical:
“PEX pipe was conclusively shown to be freeze tolerant up to 400+ cycles.”
Now the honest part. PPI does not publish a PEX-A versus PEX-B freeze ranking, and we won’t invent one. What is documented is that PEX-A has stronger elastic memory, the same property behind expansion fittings and kink recovery. That’s why it often gets specified for crawl spaces, garages and unheated attics.
PPI is also explicit that no PEX system should be intentionally subjected to freezing, and that there are situations where freezing water can damage or burst it. Freeze-break resistant is not freeze proof. If you have exposed runs in an unconditioned space, have someone walk them before winter.
Not sure whether your exposed runs are protected? We answer the phone live, 24/7, at (410) 618-3115, and a walkthrough of the crawl space beats a January surprise.
Every length of PEX carries a material designation code such as PEX 5306. Here’s what each digit tells you.
First digit, chlorine resistance (tested to ASTM F2023, minimum 50-year extrapolated life):
Second digit, UV resistance (tested to ASTM F2657): 1 = 1 month, 2 = 3 months, 3 = 6 months.
Third and fourth digits, hydrostatic design stress at 73F: 06 = 630 psi, 07 = 700 psi, 08 = 800 psi.
The minimum legal code for potable water is PEX 1106.
Sources: PPI guide to PEX chlorine resistance ratings (TN-53), revised October 2025, and the PEX Design Guide, Chapter 3.
The key takeaway: that first digit is a property of the specific product formulation, not of the letter. There are top-class PEX-A products and top-class PEX-B products. Uponor publishes that its PEX-A meets the highest chlorine class. SharkBite publishes that its PEX-B carries PEX 5306. So “PEX-A resists chlorine better” isn’t a supportable claim. Read the four digits and match them to whether your house runs a hot water recirculation loop.
Uponor publishes different UV ratings for products made from the same PEX-A: AquaPEX white carries 1-month UV resistance, AquaPEX red and blue carry 6-month, and hePEX carries 1 month. Same manufacturer, same type, different numbers by color.
PPI recommends that PEX not be stored or installed outdoors unless buried or protected from direct and reflected sunlight, using central Arizona as the worst-case North American exposure basis. UV damage is not visible to the naked eye.
PPI also publishes a 36-inch minimum setback from non-LED artificial light sources in residential and light commercial installations (PPI TN-72). If your basement has fluorescent shop lights running above open PEX, that setback is worth checking.
County water comes from wells 150 to 1,550 feet deep in the Upper Patapsco, Lower Patapsco, Patuxent and Aquia aquifers, treated at 13 facilities. Chlorine and lime are added during treatment. Here are the 2025 chlorine levels by service zone, from the county’s 2025 Consumer Confidence Report. The regulatory maximum (MRDL) is 4 ppm.
| Service zone | 2025 average chlorine | Range |
| Crofton / Odenton | 1.38 ppm | 1.06 to 1.43 |
| Glen Burnie / Broadneck | 1.25 ppm | 0.85 to 1.66 |
| Broad Creek | 1.44 ppm | 1.12 to 1.50 |
| Crownsville | 1.43 ppm | 0.90 to 1.60 |
| Rose Haven | 1.28 ppm | 0.77 to 1.31 |
| Herald Harbor | 1.12 ppm | 0.81 to 1.22 |
| Gibson Island | 1.07 ppm | 0.78 to 1.17 |
pH across zones in 2025 ranged from 7.20 to 8.72. For scale, the system delivered about 14 billion gallons to 128,993 customers through 1,540 miles of pipe, with more than 10,200 samples and 45,000 analyses.
Now compare that to the test. ASTM F2023 runs its chlorine-resistance testing at roughly 4.3 ppm free chlorine, at pH 6.8, with an oxidation reduction potential of at least 825 mV. PPI describes that as a deliberately aggressive water quality chosen to produce conservative results.
County water in 2025 tested at roughly 1.1 to 1.4 ppm at pH 7.2 to 8.7. The 50-year rating on the pipe is built on conditions harsher than what these homes actually run.
So for a typical Anne Arundel home on county water, chlorine resistance usually isn’t the deciding factor. It becomes the deciding factor when the house has a hot water recirculation loop running 12 or 24 hours a day, because that’s precisely what the 3 and 5 digits exist for. You can look up your own zone’s numbers in the Anne Arundel County drinking water quality reports and ask your plumber to match the pipe to them.
Home Innovation Research Labs tested three PEX layouts with real fixtures at 40, 60 and 80 psi static pressure, at 60 feet and 100 feet to the farthest fixture. The results are published in the PEX Design Guide, Chapter 8.
| Layout | Time to reach above 100F at 60 psi, 100 ft | Notes |
| Parallel (home-run) | 46.3 seconds | Most stable pressure with several fixtures running |
| Trunk and branch | 71.9 seconds | Higher residual pressure at a single fixture |
| Zoned remote manifold | 71.6 seconds | Higher residual pressure at a single fixture |
All three layouts delivered adequate flow and pressure to a fixture 100 feet away, even at source pressure as low as 40 psi. Water and time savings of 30% to 40% were identified for the parallel layout compared to the other two.
Read that table again. Layout moved hot water wait time by about 25 seconds. The letter on the pipe moved it by zero. The decision most homeowners are searching for is not the decision that changes their daily experience.
One more finding from Chapter 3 worth knowing: fast-closing valves on washing machines and ice makers can produce instantaneous spikes of 300 to 400 psig. In Home Innovation testing at 2.5 GPM with 130F water, peak pressure at the valve reached 181 psi for Type L copper versus 109 to 113 psi for the two PEX samples, a reduction of up to 40%. Copper is roughly 180 times more rigid than PEX, which is why the plastic absorbs the shock.
It can feel uncertain when one joint fails and you’re not sure whether that’s the start of something. A few things we look at:
If you’re not sure where the water is going, leak detection and repair usually answers that before anyone talks about scope. If the trouble is between the meter and the house, that’s a water line replacement conversation, which is a different job with different permitting than interior repiping.
We don’t publish repipe pricing, and we’d be skeptical of anyone who does without seeing the house. Fixture count, layout, access and drywall repair all move it. Someone has to walk the property.
You’ll read on a lot of pages that code requires 18 inches of metal pipe at the water heater. That rule is UPC 604.13, from the Uniform Plumbing Code. Anne Arundel County uses the 2021 International Plumbing Code, which routes the question through manufacturer instructions instead.
What PPI’s April 2026 guide actually says, in Chapter 9:
Which rule applies to your house depends on the model code your jurisdiction adopted and on what your specific water heater’s instructions say. That gap between a general internet rule and your actual heater is one of several places where a licensed plumber’s judgment separates a passing inspection from a failed one. If you’re planning a water heater installation alongside a repipe, the two decisions should be made together.
Three current requirements shape any repipe here.
1. The adopted codes. Per the county’s published Anne Arundel County adopted building and plumbing codes page, with changes effective 05/25/2026: plumbing work follows the 2021 International Plumbing Code, new residential 1 and 2 family construction follows the 2021 IRC, and repairs to existing structures follow the 2021 IEBC.
IPC Section 605.16 requires that PEX fittings comply with the applicable standards in Table 605.5 and be installed per the manufacturer’s instructions, and that PEX tubing be factory marked with the standards for the fittings its manufacturer specifies. Push-fit joints must conform to ASSE 1061 and follow manufacturer instructions.
Read that again and notice what the code does not say. It never says use PEX-A or use PEX-B. It says the tubing marking and the manufacturer’s instructions govern.
2. Maryland’s code reference changed in late 2025. COMAR 09.20.01.01, the State Plumbing Code regulation under the Board of Plumbing, was amended effective November 24, 2025. The Board now adopts the most recent versions of the IPC, IRC, IFGC, NFPA 54 and NFPA 58 as they’re amended or updated over time. Regulations .02 through .04, which held Maryland-specific modifications to those codes, were repealed the same date. In practice, Maryland’s plumbing code now tracks the current model code rather than a frozen edition.
3. Lead-free requirements still apply to your fittings. COMAR 09.20.01.05 defines lead-free as no more than a weighted average of 0.25% lead across the wetted surface of pipes and fittings, and no more than 0.2% for solder and flux. Platings, coatings or acid wash treatments can’t be used to meet that limit. Piping supplying a potable water heater is on the lead-free list.
PPI adds that all brass and bronze PEX fittings for potable water must be certified to NSF/ANSI/CAN 372 for the lead limit and NSF/ANSI/CAN 61 for drinking water safety, and notes that the Uniform Plumbing Code requires copper alloy fittings and valves with more than 15% zinc to resist dezincification and stress corrosion cracking under the NSF/ANSI 14 test.
Turn that into two questions for any contractor you’re considering:
Those are fair questions, and any licensed plumber should be comfortable answering them.
Is PEX-A better than PEX-B? No. The letters describe manufacturing methods, not quality grades. Both have to meet the same requirements under ASTM F876 and ASTM F877, and PPI states the designations aren’t tied to any rating system.
Can you use expansion fittings on PEX-B? Only if that specific tubing is marked for it. ASTM F1960 cold expansion relies on the tube retracting onto the fitting, which is why it’s associated with PEX-A. PPI’s instruction is to read the print line or ask the manufacturer, since not all fittings work with all PEX.
Does PEX-A or PEX-B have better water flow? The tubing is identical in size. Both are copper tube size, SDR 9, with the same inside diameter at every nominal size. Flow differences come from fittings and layout, not the letter.
Does PEX-B burst at a higher pressure than PEX-A? Both must meet the same minimums: at least 160 psi at 73F and 100 psi at 180F, plus 720 hours at 150 psi and 210F to cover a water heater malfunction. Some manufacturers report figures above the minimum, but a plumbing system is designed to the standard, not to a marketing burst number. Because of that 720-hour requirement, PEX doesn’t need a special temperature and pressure relief valve.
Which PEX lasts longer? Every PEX product for potable water must show a minimum extrapolated time to failure of 50 years under ASTM F2023 chlorine testing. What varies is the class it was tested at, and that’s the first digit of the code printed on the pipe.
Which PEX do plumbers actually use? Both. PEX-B is more widely stocked across general distribution. PEX-A shows up where routing is tight, where kink recovery matters, or where the contractor runs an expansion system. Ask which system your contractor is tooled for, because tools, fittings and tubing all have to match.
Can I mix PEX-A and PEX-B in the same house? The sizes match and many fittings are approved for both. But PPI warns against mixing components from different manufacturers even when parts look identical, and the IPC requires installation per manufacturer instructions. This is work for a licensed plumber, not a mix-and-match project.
How do I tell which PEX I already have? Look for the print line, which repeats every 5 feet or less. It carries the size and SDR 9, the manufacturer, a production code, the material designation code, the standards met, pressure ratings, the certifier’s mark, and the approved fitting standards. It doesn’t always spell out “PEX-A” or “PEX-B,” which is why identification is best confirmed by a plumber who reads these daily.
Is PEX safe for drinking water? PEX tubing and components must be certified to NSF/ANSI/CAN 61 for health effects, NSF/ANSI/CAN 372 for lead content, and NSF/ANSI 14. PPI states PEX tubing contains no lead, no harmful VOCs and no BPA, and that products are tested at pH from 5.0 to 10.0 at both cold and hot temperatures.
How long does a whole-house repipe take, and what does it cost? It depends on fixture count, layout, access and how much drywall has to be opened, so we don’t quote it without walking the house. Scheduling a walkthrough is the fastest way to get a real number instead of a range that won’t hold.
Do I need a permit to repipe in Anne Arundel County? Yes. A plumbing permit is required for adding or relocating fixtures and piping, including piping installed for future use, and only licensed plumbers may apply for plumbing trade permits.
That last permit point is the honest reason to make a call rather than shop tubing. A repipe here is permitted, inspected work, and the permit is pulled by a licensed plumber, not by the homeowner. Everything above, the print line, the fitting standard, the material code, the water heater connection, gets checked against the 2021 IPC by someone with a clipboard.
Abend Services has been family-run in Maryland since 1952, we’re woman-owned and operated under Katie Abend, and we hold Maryland master plumber license MP #2316. We were voted Best of Annapolis Plumber in 2025, and we answer the phone live, around the clock.
If you’re weighing a repipe, call (410) 618-3115 and we’ll walk the house, read what’s already in your walls, and put the right pipe and the right fitting system in writing. We handle plumbing services in Annapolis and across Arnold, Brooklyn Park, Crofton, Glen Burnie, Millersville, Odenton, Parole, Pasadena and Severna Park.
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