This is what our family has done with RVs and boats (Recreational Vessels) for decades. The only thing that is an issue is if it is old enough (mine is) to have sweat copper water system. Then any freezing can and may do serious damage that is either expensive or a lot of work to repair. But, if it is new enough to have plastic or even better a PEX water system then a little freezing in the sagging lines is a non-issue. It is, however, important to look for the low places that have metal fitting and be certain that those places are clear.
Matt