Types of PEX
PEX tubing is classified into types based on the way that it is manufactured. These types are simply referred to with letters: a, b, and c. PEX-AL-PEX is another type of PEX tubing that is completely different from either PEX a, b, or c.
PEX-a is manufactured through the “Engel method.” The cross-linking is done above the crystal melting point which provides more consistent and uniform cross-linking. The process does, however, tend to take longer and be more expensive than the other two methods. In other words, its quality is balanced by its price.
PEX-a is most notably manufactured by Uponor and Rehau Incorporated.
PEX-b is produced through the silane method. Cross-linking is performed between cross-linking agents. This process is quickened with heat and moisture which makes this manufacturing process relatively cheap and simple.
Most manufactures produce PEX-b tubing.
PEX-c is formed through electron beam processing. The cross-linking is done below the crystal melting point and creates less uniform cross-linking than either the PEX-a or the PEX-b process. However, this method is the more environmentally friendly and cleanest method since it doesn’t involve any other chemicals or produces any other dangerous by-products.
PEX-c is most notably manufactured by Roth Industries.
PEX-Al-PEX is made of an aluminum layer sandwiched between two layers of PEX. The aluminum layers acts as an oxygen barrier that prevents molecules of oxygen from mixing with the water flowing through the pipe. The aluminum also increases the strength of the piping and allows the aluminum to bend better. PEX-Al-PEX is used most commonly for radiant heating systems.
Most manufacturers that sell PEX tubing also sell PEX-Al-PEX for radiant heating systems.