We're having to stay in the rv during the winter for at least half of the time while we work on a project out in the sticks. The last couple of weeks have been freezing weather (even in Texas!) and we needed to dump the black water. Well, it was frozen...not a pretty sight. Major amounts of running water through the system got maybe half of it out. Is there some form of antifreeze solution that can be added to the tank while still in use? We can't winterize for storage since it will be in use. Any ideas? Thanks to all.