PEX piping question for plumbers

dougrainer wrote:

I don't think there are different grades of PEX. This is the FIRST time I have seen PEX split from freezing. MY crimp tool took a lot of force to crimp the ring that I replaced on both. Doug

All PEX is the same basic material and has to meet the same ASTM/CSA/NSF standard. It's manufactured using 3 different processes - designated PEX-a, PEX-b or PEX-c and each version has different characteristics as explained here.
PEX-a has the best properties and it can be severely kinked and damaged and brought back to original shape by heating with a heat gun. PEX-a can expand to 3 times it's original dia. and will return to its original size which makes it freeze resistant. I *think* Pex-a is what's most widely sold and all I've run across. PEX made by Zurn is Pex-b with specs here.. PEX-a costs more.

The hotter the operating temp., the lower the pressure rating PEX has - standard rating 100 psi @ 180F & 160 psi @ 73F (printed on exterior).

PEX should not be exposed to direct or indirect UV. Different brands/types can have different exposure limits. PEX exposed to fluorescent lighting indoors can be damaged from the UV rays. From experience, plumbing wholesalers will not take back PEX due to possible UV damage. Now that someone mentioned it, our low point drain PEX and valves hang down at the very rear of our TT and quite exposed to UV ray - may be a good idea to do something about them. A removable plastic sleeve of some sort might all that's needed.

According to the Plastics Pipe Institute, PEX is freeze resistant. It is not freeze proof though. Can't find any info. on typical min. temps. before damage occurs. UV damage will increase the chance of freeze damage.

Plastic PEX fittings used in RVs are made from a polysulfone/polyphenylsulfone blended polymer and have a pressure rating of 100 psi @ 180 deg. F and 160 psi @ 73 deg. F. Like PEX, these fittings need be protected from UV. Uponor lists 30 days as max. exposure time. Temp. operating range from -50C (-58F) up to 200C. Providing not exposed to UV, should not fail under low temps in most cases except maybe somewhere like Alaska. I can't see any reason to change these out for brass.

A PEX crimper will require the same force to crimp a ring on 100 or 160 psi. Try crimping a ring without any pipe. Standard crimper can be difficult inside RV cabinetry and there is a pocket crimper for tight spaces that uses vise grip pliers. I may get one in case if needed for an emergency on the road repair.

Not a plummer by trade, but google is my friend...