[JRTJH]

RV antifreeze will "freeze slushy" and that is normal. The claim, "protects to -50F" doesn't mean it won't freeze, but rather that when it freezes (and it will) the "liquid turned thick or turned solid" won't expand at temperatures above -50F. Even though the RV antifreeze will freeze, since it doesn't expand, it won't damage the plumbing by causing cracks through expansion.

Frozen RV "pink stuff" is perfectly normal. The problem: You can't tell if you've displaced all the water that was in the system, so there's a chance the water will freeze. Hopefully there is enough antifreeze mixed in that the expansion of the water won't be so great as to cause damage. Which is another reason to use air to blow as much water from the system as possible before adding RV pink stuff.......