PEX tubing (cross-linked polyethylene) began gaining popularity in in-floor heating systems in the 1980’s and 1990s, however it wasn’t until early 2000’s that it became more widely adopted as the standard for in-floor heating applications. Its durability, cost-effectiveness, and flexibility all helped increase its popularity among builders. Yet, did you know that there is more than one type of PEX tubing? Let’s go over the different types and their preferred uses.
PEX-A: This variation is the most flexible PEX made. All plastic hoses retain something called “coil memory.” The more coil memory a hose has, the more difficult it is to lay down. PEX-A has little or no coil memory which allows it to lay down more easily. Also, any kinks made during installation can be removed simply with a heat gun.
Its structural integrity also allows it to enjoy degrading and cracking at a lower rate than other types. It works well in freezing temperatures since it can expand without fear of bursting.
The downside of PEX-A is the cost. It can cost up to 2-3 times more than the other variations. So, unless your installation requires a lot of bending and flexibility, you should reconsider.
PEX-B: This is the clear winner between the variations. It’s the most durable, has a great price-point, and is the most resistant to degradation. While not as freeze-resistant as PEX-A, it works well enough, especially when used in in-floor heating projects.
PEX-B has the highest oxidation resistance, meaning that cracking is rare due to its high integrity.
Downsides to PEX-B are its stiffness. It works well when used with Heat-Sheet insulation and other staple/foam insulation installations, however the high coil memory makes it difficult to work with. Any kinks or damage to the tube can not be simply repaired with a heat gun and a coupling technique must be used.
PEX-C: PEX-C is the least flexible and is best used for shorter, straighter installations without a lot of bending or sharp corners. It’s good for temporary repairs in your plumbing system and can be had for a reasonable price compared to the other two variations.
The definite downside of PEX-C is that it has the best chance to degrade early due to oxidation. Its stiffness makes it more prone to cracking in case of oxidation. While PEX-C is suitable for hydronic heating use, it offers little practical advantage over the other two variations.
Not everyone has the same plumbing needs and each hydronics installation is unique, so finding the tools that work for your project is important. Consulting with a plumbing professional can provide more insight into what you may need.