brass, stainless, or EP/plastic for Well service line fittings

[ohnoflood]

Where the black polyethelene service line enters this particular structure is by far the most freeze-prone area. The structure is an elevated "mini house" with an insulated, heat-taped plenum taking the poly from below frost line up into the space between floor joists. But, power outages occur, and despite the insulation this area would likely begin to freeze before anything inside the structure or below ground.

A hard freeze of all the tube would clearly cause a failure, but on the margins my guess is good design & material choice could make the difference between a winter emergency vs not. To that end I've minimized all other fittings, and am using expansion fittings of course, but have a mandatory coupler between the 1" black poly and 1" pex-a (barbed to expansion) in the joists.

I have all three of these options, thank you for your feedback on which one is the most robust against partial-freezing.

• brass single-piece Ferguson didn't have anything like this, but I found this single-piece barbed --> ProPex
  • No well water report (won't have it until this is installed) - all things equal brass should be the most susceptible to any water quality issues, though.
• stainless, as barbed --> NPT --> ProPex
  • available in both machined, and swaged. I'd expect the swaged fitting to be work-hardened; stainless is already brittle relative to plastic & brass, so I assume machined is preferred (??)
• EP/plastic, again as barbed --> NPT --> ProPex
  • Note, this fitting occurs near a 90 and has some accomodation in the insulation, so I don't believe the location has any notable stress that might make me concerned (Freezing aside) about EP

Thank you!

Here's the one-piece brass if you're curious: