Several years ago I was using my RV occasionally during the winter and did not want to completely winterize after each trip using the pink antifreeze because of the hassle. What I did do was blow out the water lines using an air compressor (40 psi) after every trip. My rationale was that the lines could not freeze if there was no water in them. I did put antifreeze in the P-traps though. It worked then and never did crack a line. I know it got cold enough because the copper water pipes in my cabin cracked in several spots during the freeze.
