So Youroo, Just cause I now live in Fl. what makes YOU think I don't RV up North, and for your information it does freeze here in Northern FLorida.
Besides, Water freezes at 32 degrees. It doesn't make any difference if it 30 or minus 30, the water has frozen, expanded and turned to Ice.
Again why don't you, and others do like I do and just drain your RV's water lines, water heater, tanks, etc when storing your RV's? It's Easier and Less Expensive than buy anti freeze and pumping into your lines.