Is there a freeze-proof copper pipe?

I've not tried it, but since water reaches its maximum volume before it freezes (ice floats), I've had the thought that a water hammer arrestor would do the job, giving the water a place to expand before it freezes solid.

No such luck. Even with water off and the pipes poorly drained, residual water can freeze and break pipes. I have never had it happen, but I have had a water filter break because there was a little water left in it.

Supposedly pex will can tolerate freezing. Perhaps someone will elaborate on that.

It may help in some cases, but often the arrestor is too far away. Water expands 17% when it freezes and can easily do lots of damage.

PEX would be a better product in a potential freeze up though.

It's an old story... If you run pipes in an outside wall in a climate subject to freezing, you're going to have trouble.

Best to relocate the pipes in the heated space and cover them with insulation if there is any doubt.

Beachcomber

I would put heat tracing on them and insulate.