ASTM F1281 PEX pipe (cross-linked polyethylene) is widely used in modern plumbing systems due to its flexibility, cost-effectiveness, and durability. However, there are different types of PEX pipe available, with the most common being PEX A and PEX B. While both are designed to serve similar functions, there are key differences between them. If you're wondering whether your plumbing system uses PEX A or PEX B, this article will guide you through the various ways to identify which type of PEX pipe you have.
What is PEX Pipe?
ASTM F1281 PEX pipe is a plastic piping material that is used for distributing hot and cold water in plumbing systems. It is made by cross-linking polyethylene molecules, which gives the pipe its flexibility, resistance to corrosion, and overall durability. PEX is popular because it can be bent around corners without the need for additional fittings, and it is easier to install than traditional copper or PVC pipes.
There are three main types of PEX pipes: PEX A, PEX B, and PEX C. The primary difference between PEX A and PEX B lies in their manufacturing process and the characteristics that result from that process.
What's the Difference Between PEX A and PEX B?
Before diving into how you can identify which type of PEX pipe you have, it's essential to understand the fundamental differences between PEX A and PEX B.
1. Manufacturing Process
PEX A: PEX A is made using the "Engel" method, which involves cross-linking the polyethylene molecules through a peroxide reaction. This process results in a more flexible and pliable material. PEX A also has the advantage of being the most resistant to kinking and can be easily re-shaped if bent.
PEX B: PEX B is made using the "Silane" method, where the cross-linking is achieved through a moisture-cure process. While PEX B is still flexible and resistant to freezing, it tends to be slightly stiffer than PEX A.
2. Flexibility and Kink Resistance
PEX A is more flexible and has better resistance to kinking compared to PEX B. PEX A pipes can be bent to a tighter radius, making them more suitable for installations in tight spaces.
3. Price and Availability
PEX B tends to be less expensive than PEX A due to its different manufacturing process. However, PEX A is often favored for its greater flexibility and ability to "self-repair" kinks with heat.
4. Fittings and Connections
PEX A: PEX A is often used with the "expansion" fitting method. This involves expanding the pipe and fitting it over a specialized metal insert before contracting back around the fitting. This connection method is more secure and leak-resistant.
PEX B: PEX B typically uses crimp or clamp fittings, which involve crimping a metal ring around the pipe and fitting to create a seal. This is a more common method for DIY projects, as crimping tools are widely available.
How to Identify PEX A vs. PEX B
There are several ways you can determine whether your plumbing system uses PEX A or PEX B pipe. Here's a breakdown of the most reliable methods:
1. Check for Manufacturer Markings
One of the simplest ways to tell whether you have PEX A or PEX B is by checking the markings on the pipe itself. Manufacturers typically stamp important information along the length of the pipe, including:
Type of PEX (A, B, or C)
Size of the pipe
Pressure rating
Manufacturing date or batch number
For example, if you see a stamp that reads "PEX-A" or "PEX Type A," you have PEX A. If it says "PEX-B" or "PEX Type B," then you are dealing with PEX B.
2. Examine the Pipe's Flexibility
If the pipe appears very flexible and can be bent with minimal effort, especially when compared to a more rigid or stiff pipe, it is likely PEX A. PEX A is known for its extreme flexibility and resistance to kinking. On the other hand, PEX B is somewhat stiffer and may resist bending as easily as PEX A.
3. Look at the Fittings Used
Another way to determine which type of PEX you have is to examine the fittings used in the system. If you notice that the connections have been made using expansion fittings or a special expansion tool, it's likely you have PEX A. This method is commonly used with PEX A for a more secure, permanent connection.
If you see crimp or clamp rings, especially on smaller-diameter pipes, the system is probably using PEX B. These fittings are more common with PEX B installations.
4. Check for "Memory" Ability
PEX A has the ability to "remember" its original shape when heated. This means that if the pipe is kinked or bent, applying heat (like with a heat gun) can restore the pipe to its original shape. PEX B, while still flexible, does not have this same "memory" property, so a kinked pipe cannot be easily repaired with heat.
5. Consult Your Plumbing Professional
If you're still unsure about the type of PEX pipe in your home, consult a plumbing professional. They can inspect your plumbing system and help you identify whether you have PEX A or PEX B. A plumber will be able to determine the type based on installation techniques, pipe material, and even the fittings used.
Why Does It Matter Which Type of PEX You Have?
Knowing whether you have PEX A or PEX B in your plumbing system can help with several aspects of maintenance and repair. For instance, if you're considering expanding your plumbing system or replacing parts, you need to know which type of pipe is already in place so that you can use compatible fittings and materials.
Additionally, the flexibility and resistance to kinking of PEX A might influence your decision when selecting pipes for a new installation, especially in tight spaces or areas where bending is required. On the other hand, if you are working with a tight budget, PEX B offers a cost-effective option without sacrificing significant performance.
Common Misconceptions About PEX Pipe
There are a few common myths surrounding PEX pipe that should be cleared up:
1. PEX A is Always Better than PEX B
While PEX A is more flexible and resistant to kinks, PEX B is still a solid choice for most plumbing applications. It offers a lower price point and performs well in many standard water supply systems.
2. PEX Is Unsafe for Drinking Water
PEX pipe is approved for use in drinking water systems by major regulatory agencies such as the NSF. Both PEX A and PEX B are safe for use with potable water, as long as they are properly installed and meet local plumbing codes.
3. PEX Can't Be Used Outdoors
PEX pipe can be used outdoors, but only if it is properly protected from UV rays. PEX that is exposed to sunlight for prolonged periods will degrade over time. UV-resistant PEX should be used in outdoor applications, or the pipe should be buried underground or protected with insulation.
Conclusion
Knowing whether you have PEX A or PEX B pipe is important for understanding your plumbing system's flexibility, longevity, and ease of repair. By checking for manufacturer markings, assessing flexibility, and looking at the types of fittings used, you can identify which type of PEX is in your home. If you are still unsure, consulting a professional plumber is always a safe bet.
Understanding the differences between PEX A and PEX B will not only help you maintain your plumbing system more effectively but also guide you when expanding or upgrading your pipes. No matter which type you have, both PEX A and PEX B offer significant advantages over traditional copper or PVC pipes, including greater durability, easier installation, and better resistance to corrosion.
