I have seen both steel pipe and PCV with water in them freeze. They both can burst, but the steel usually maintains some structural integrity which would still hold up a box. The PCV, not so much. I would be concerned if a PVC model would be expected to endure any ice-overs. I'm guessing the box posts are not intended to be left out through the winter? If that is the case, my point is moot. It would be nice to leave at least the posts in place so that the box is all the gets stored away for the off season however.
