The Differences Between Different PEX In-floor Pipes


When it comes to radiant in-floor pipe, one stands out as the superior choice – PEXa. Currently there are three methods of crosslinking polyethylene piping known as PEXa (the Engel Method), PEXb (the Silane Method) and PEXc (the E-beam Method).

REHAU PEXa pipe is the pipe that Eden Energy Equipment sells, but in order to understand all its benefits to you, you must also understand how each type of pipe is made.

All three of these processes meet the requirements of ASTM F876 and F877 and are suitable for potable water distribution, but they are not at all equal when it comes to the final product.

PEXb pipe is made using either steam or hot water after the extrusion process. Compared to PEXa pipe, which has a degree of crosslinking of approximately 85%, PEXb pipe has a degree of crosslinking of 65-70% and is not evenly crosslinked because it is done after the extrusion process. This means that the pipe has less thermal memory making it more difficult to repair if the pipe is kinked.

PEXc pipe uses an electron beam for crosslinking and has a degree of crosslinking between 70-75%. The pipe also has less thermal memory than PEXa pipe making it difficult to repair kinks, similar to PEXb pipe.

  • With PEXa pipe, the crosslinking is done during the extrusion process, not after, which gives it a degree of crosslinking of up to 85%. Because the crosslinking happens during the extrusion process, it has a more uniform product making it more durable. The differentiations of PEXa pipe versus PEXb and PEXc pipe are as follows:
  • PEXa has the highest resistance to splitting or cracking: Because of the high level of crosslinking during the manufacturing of PEXa pipe, it is less likely to crack and more importantly, if the pipe does crack it is less likely to leak because the crosslinking prevents it from spreading.
  • PEXa pipe has the greatest flexibility/bend radius: PEXa pipe has the greatest flexibility when it comes to PEX pipe. This means that when you need to do 6” centers with 5/8” pipe for maximum BTU output per square foot, you can. On 1/2” pipe, you can get the radius down to less than 4”.
  • PEXa is very hard to to kink & has thermal memory: Because of its design, the PEXa pipe is extremely flexible, which means that it is less likely to kink on a tight radius. It also has thermal memory which means you can heat it up with a heat gun and remove any kinks, eliminating the need to fix it with a mechanical fitting or having to replace the pipe.
  • PEXa pipe has shape memory: PEXa pipe not only has thermal memory, but it also has shape memory, which means when you expand the pipe for use on your fittings, it goes back to its original shape for the best possible fitting connection. Because of this, it is less likely to have a bad connection or leak.

The REHAU product line offers contractors a variety of advantages for their in-floor installations and we encourage you to take advantage of all of them. More importantly, if you have questions call and ask us at 1-800-665-3336.

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