Michael,
Does it have any "Made In" marking? I am betting it is China. Does it say anything about NSF on the PEX? While PEX for hydronic use does not have to be NSF listed, if it is, then the facility, will have met NSF guidelines.
Your PEX may not have been crosslinked fully. One of the dirty little secrets of Chinese PEX is that the crosslinking process, which for PEX B involves a steam chamber and hot water ran through it for 24 to 48 hours, is often skipped. This is particularly true for O2B PEX or when they know it is going to hydronic use. I believe they are betting that the end user will finish the crosslinking with their hot water. This saves them perhaps 2 to 4 cents per foot. I know this from sending samples of Chinese PEX for testing.
Jeff Zack
Owner,
Z Supply, LLC