I always have a drain valve. It is not just what gets in the line, water standing in the tank will cause corrosion. A water filter inline is also a good idea. I was going to put one in my when I rebuilt it but there was no room where I set it up. I will redo it and put the air feed on top so I can put the filter inline. If you are just doing tires it is not as big a deal compared to lockers off the tank.
I have jeeps. I do shit to them.