Plumbing is probably PEX so the pipes are not as vulnerable as the valves. There are replacement valves that do not require a crimper. They work and are worth putting in your spare kit if you are going to winter camp. I would be very leary of salt as an anti freeze but the pink stuff is at Walmart. Not tasty but not corrosive and safe if you drink some. That will freeze but shrinks when it does so nothing gets broken. I will be replacing plumbing in the spring to drain and separate the outside shower as that is a freeze point even when the unit is warm. ;-)