I understand that PEX for radiant heat should have an oxygen barrier so that ferrous materials in the radiant heat plumbing won't rust. An oxygen barrier is not necessary only if your radiant heat system is 100% iron-free.
So, that fact possibly translates to and interferes with my idea to replace some of my galvanized steel pipe plumbing system with PEX during a bathroom remodel. I would just use PEX with an oxygen barrier, but I don't think any such PEX is rated for potable use.
Maybe oxygen barriers are needed in radiant only because the water is constantly reused. Perhaps it's not an issue in supply plumbing, where the water is always "new" water.
I'd appreciate any insights that you all may have.