We are replacing PB pipe which runs from the crawlspace, through an exterior wall, and to the kitchen sink. The PB was connected to perfectly lovely copper pipe (1/2") which they chopped out and left lying there. The pH of our water is 6 which may explain why they got rid of the copper. Still, the whole rest of the house has copper. It was built in 1937 and 1983ish.
--We have mice--God's own Rodent World. Let's assume it will take us months to get rid of them, if ever.
--The supply lines run directly in front of the foundation vent. Here in NC, it frequently gets below freezing, although obviously not arctic conditions.
We're thinking: Sharkbite CPVC to the copper. Cover CPVC with foam insulation, then cover the insulation with metallized tape to hopefully keep the rodents from finding it tasty. Yes, the foundation vent will be covered in the winter, but there is no heat at all in this area of the crawlspace.
Other ideas? Oh, and we're both uncomfortable with the idea of sweating copper joints. We're not plumbers, just reasonably careful people.
With a PH as low as 6.8 being detrimental to copper pipes I would suggest an acid neutralizer be installed to protect your remaining copper pipes. I would also go with whatever other treatment is recommended per your water test.
I would suggest CPVC would probably be best in your application as the mice do have a likeing for some types of PEX in particular the brand I have pictured below... LOL
Your climate is not all that bad and as long as you take appropriate measures to prevent freezing you should be okay. Block that vent in winter and insulate the pipes. If you do get a freeze get some heat in that crawl space right away before you get a split.