PEX-A vs. PEX-B vs. PEX-C: Differences and Best Uses
PEX-A, PEX-B and PEX-C are manufacturing classifications, not quality grades. The letters describe how the polyethylene is cross-linked during production. No type is automatically better than the others. The right choice depends on the product’s tested performance, certifications, bend radius, fitting compatibility and intended application.
Performance itself is rated, and it's printed right on the tubing. Under ASTM F876, every PEX product, whether A, B or C, carries a four digit designation code on its print line covering chlorine resistance, UV resistance and pressure rating. The highest available is PEX 5306, reflecting the top chlorine resistance and UV classes. Because that rating reflects tested performance rather than the manufacturing letter, it's a sounder basis for selection than whether the tubing is PEX-A, PEX-B or PEX-C. Keep in mind the code shows that a product meets a class, not by how much it exceeds it.
PEX tubing with a printed rating of 5306 indicates that it will be suitable for installation areas of constant hot water circulation and has a maximum UV exposure of six months.
the UV protection rating is important because certain construction practices and storage conditions subject PEX tubing to sunlight exposure for an extended period of time. UV testing confirms the longevity of the PEX tubing under various lengths of UV exposure
| PROPERTY | STANDARD | 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Chlorine Resistance | F2023 | Not tested or rated | 75 % at 73°F and 25 % at 140°F | Reserved | 50 % at 73°F and 50 % at 140°F | Reserved | 100 % at 140°F | ... | ... | ... | ... |
| Minimum UV Resistance | F2657 | Not tested or rated | 1 month | 3 months | 6 months | ... | ... | ... | ... | ... | ... |
| HDS for water at 73°F | ... | ... | ... | ... | ... | ... | ... | 630 | ... | 800 | ... |
See Viega's Understanding PEX Tubing Codes whitepaper.
In general:
- PEX-A is commonly associated with high flexibility.
- PEX-B products can offer a balance of flexibility, dimensional stability and application-specific performance, depending on the manufacturer and system.
- PEX-C uses an electron-beam manufacturing process and should be evaluated using product-specific data.
The tubing is only one part of the decision. Always consider the fittings, connection method, tools, valves and other components as a complete system.
PEX-A, PEX-B and PEX-C at a glance
| FACTOR | PEX-A | PEX-B | PEX-C |
|---|---|---|---|
| Manufacturing method | Peroxide or Engel | Silane or moisture cure | Electron-beam irradiation |
| General flexibility | Commonly high | Moderate to high | Varies by product |
| Common consideration | Tight routing | Plumbing, heating and press-system applications | Product-specific applications |
| Key selection factor(s) | Bend radius and fitting compatibility | Ratings, resistance and fitting compatibility | Manufacturer data and approvals |
*These are general characteristics. Actual performance varies by manufacturer and product.
What is PEX?
PEX is cross-linked polyethylene tubing used in approved plumbing, hydronic heating and other piping applications.
Cross-linking improves characteristics such as temperature resistance, pressure performance and long-term durability. PEX-A, PEX-B and PEX-C use different methods to create that cross-linking.
Products must meet the same minimum standards while differing in bend radius, chlorine resistance, temperature limits, pressure ratings and compatible connection systems. That is why the PEX letter should not be the only factor in product selection.
What is PEX-A?
PEX-A is made using the peroxide or Engel method. Cross-linking occurs as the tubing is extruded.
It is often considered when flexibility is a priority, including layouts with tight routing or fewer directional fittings. However, bend radius, approved fittings and performance ratings still depend on the specific product.
PEX-A may be appropriate when:
- The installation requires flexible routing
- The tubing is approved for the application
- Compatible fittings and tools are available
- Its temperature and pressure ratings meet project requirements
What is PEX-B?
PEX-B is produced using the silane or moisture-cure method. Cross-linking develops during and after extrusion.
PEX-B is not a lower grade than PEX-A. The letter identifies how the tubing is manufactured, not its overall quality.
PEX-B may be appropriate when:
- The tubing is approved for potable water or heating
- Its temperature, pressure and resistance ratings meet the application
- A compatible press connection system is preferred
- The product’s bend radius works with the layout
PEX-B is used in many plumbing and heating applications. Depending on the product, it can provide a practical balance of flexibility, dimensional stability, chlorine resistance and compatibility with press fitting systems. What turns those characteristics into reliable, in-field performance is complete-system compatibility.
That's Viega's approach: engineering and validating the tubing, press fittings, valves and tools all together as one system, so every connection is backed by tested compatibility rather than component specs alone.
What is PEX-C?
PEX-C is cross-linked after extrusion using electron-beam irradiation.
Its flexibility and handling characteristics vary by product. It may be suitable for plumbing or heating applications when the tubing has the required approvals, ratings and compatible fittings.
As with PEX-A and PEX-B, selection should be based on documented performance rather than the manufacturing letter alone.
How do you choose the right type of PEX?
Start with the application, then evaluate the actual product.
Potable-water plumbing
Confirm potable-water certification, chlorine resistance requirements, temperature ratings and fitting compatibility. Also consider product availability and how your crew will make each connection.
Domestic hot-water recirculation
Recirculation systems can expose tubing to continuous heat, flow and water chemistry. Review the manufacturer’s recirculation limits and product-specific technical data.
Radiant heating
Confirm temperature and pressure ratings, tubing size, loop requirements, manifold compatibility and any required barrier properties. See Viega's heating and cooling solutions.
Tight spaces
Compare the product’s documented bend radius. Do not assume that every PEX-A product is more flexible than every PEX-B or PEX-C product.
Press connection systems
The tubing, fitting, sleeve, tool and press profile must be approved as a complete configuration. The PEX manufacturing letter does not determine which connection methods can be used.
Which type of PEX is best?
There is no universal best type of PEX.
The best option is the product that meets the project’s application, performance and installation requirements. Focus on tested data and complete-system compatibility rather than selecting tubing by letter alone.
Looking for a PEX-B system?
Viega offers PEX-B tubing as part of the Viega PureFlow® system. PureFlow® includes compatible tubing, press fittings, valves and other system components for approved residential and commercial applications.
Applicable PureFlow press fittings include Smart Connect® technology, which is designed to help identify unpressed connections during system testing.
Viega also supports contractors, engineers and specifiers with technical documentation, application support, engineering services and hands-on training.
Explore Viega PureFlow® PEX-B
Review Viega PureFlow® PEX-B tubing, press fittings and system components to determine whether the system meets your project requirements.
PEX Comparison FAQs
-
Can you mix PEX-A, PEX-B and PEX-C in the same system?
Different PEX types can be used in the same installation, but every connection must be made with fittings and tools approved for that specific tubing. Follow each manufacturer's listed configurations rather than assuming a fitting approved for one type is approved for another.
-
Can a kink in PEX tubing be repaired?
A kink restricts flow and creates a weak spot, so it has to be addressed. Heat repair is possible on some products, but it is time-consuming and the tubing is more likely to kink again in the same spot. The more reliable repair is to cut out the damaged section and join it with a fitting, which removes the weak spot and keeps Viega PureFlow warranty coverage in place. See Why the Best Repair for Kinked PEX is a Fitting.
-
How do you read the print line on PEX tubing?
The print line lists the tubing size, applicable standards such as ASTM F876, certification marks and the four-digit performance code. Within that code, the first digit indicates the chlorine resistance class, the second indicates the UV resistance class and the final digits indicate the pressure and temperature rating. PEX 5306 reflects the highest chlorine and UV classes available.
-
How long can PEX tubing be exposed to sunlight before installation?
UV exposure limits are product-specific and reflected in the tubing's performance code. Viega PureFlow PEX tubing is rated for six months of UV exposure. Store tubing covered and confirm the manufacturer's stated UV exposure limit before leaving it exposed on a jobsite. See a manufacturer comparison.
