Stainless Steel PEX fittings have gained significant traction in recent years, and for good reason. Both cold expansion and crimp PEX fittings are commonly used in the plumbing industry alongside PEX piping. PEX piping itself comes in several varieties, including PEX A, PEX B, and PEX C—each with its own unique characteristics. But how do you know which type of PEX pipe pairs best with which Stainless Steel fitting?
In this blog, we’ll delve into the nuances of PEX piping options and clarify which fittings are ideal for each type of PEX, whether you're working with cold expansion or crimp fittings.
PEX A (Cold Expansion)
PEX A pipe can accommodate any PEX fitting, however, it is really only used with cold expansion fittings in the real world. It is typically not used with crimp PEX fittings because PEX A typically costs more, compared to PEX B due to the engel-method manufacturing process. PEX A has been
PEX B (Crimp)
Boshart's 304 series Stainless Steel Crimp are manufactured to ASTM 1807, and they are
PEX B piping is manufactured using the moisture cure method, making PEX B the most common type of PEX piping available. Why is it more common? Typically PEX B is less expensive than PEX A. PEX B includes all of the properties that are required to make to make good connections on both ASTM-2159 Plastic crimp type fittings and also ASTM-1807, metal crimp fittings. Both do not require expansion of the PEX pipe in order to make a connection.
PEX C (Crimp)
PEX C is manufactured using a cold method, that is cross linking, making this piping the least common type of PEX piping on the market. It does have the properties that are needed to make a good connection on both ASTM-1807 (metal) and ASTM-2159 (plastic) crimp type fittings that also do not require any expansion of the pipe. PEX B and C are interchangeable with the main difference being the hardness, PEX C is much softer.
Watch Out for Kinks in PEX Pipe
Although PEX C costs the least to manufacture, due to its softness, it makes it more susceptible to kinking, which is one of the main reasons why it is not commonly used. PEX A and PEX B are typically much more popular.
As technology has evolved over the years, some manufacturers have created PEX B piping that is now suitable for use with cold expansion fittings.
It is very important to note that it is the responsibility of the installer to work with the manufacturer to ensure that the piping you are using is suitable for your particular application.
Generally speaking, the average PEX B pipe is not compatible with cold expansion fittings. Using a cold expansion tool on most PEX B pipes will void warranties and ruin the pipe.
PEX A (cold expansion) pipe has "memory" which is what provides the seal around the fitting (with the help of a PEX A collar). PEX B does not have this memory. When you stretch it, it is destroyed (this is also why you must be aware of kinking the pipe).
Understand that, while you can use crimp fittings in cold expansion pipe with no issues, the reverse is not true.
If crimp fittings can be used anywhere, why would anyone solely install a cold expansion system?
Cold expansion retains the full-port of its nominal size (as in, the I.D. [inner diameter] of a cold expansion pipe is truly 1/2" as its name suggests). Crimp fittings, however, have a reduced I.D. which means that flow is restricted when using cold expansion (meaning the 1/2" moniker does not describe the I.D. of a crimp fitting).
Cold expansion pipe is also more flexible, meaning you can bend it (with a suitable radius) around corners as opposed to having to use an additional fitting.
But because crimp PEX is cheaper, that is why it is often used.
Plumbers and contractors that do repairs and remodels will also often use the system that is already in place.
There are countless other reasons why contractors use one over another. It could be boiled down to preference and familiarity more than anything else. There are great arguments on both sides of the aisle.
PEX A
PEX B
PEX C
In Conclusion:
When working with PEX fittings, whether cold expansion or crimp, the choice of piping often comes down to personal preference. However, this article will not only help guide your decision but also provide recommendations on which type of PEX pipe pairs best with each Stainless Steel fitting.
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