I leave the slide gate open and the cap off while I'm maneuvering the trailer into my shop. By the time I get it pulled inside any residual water has found its way to the ground. A few days after pulling it in the shop I close the slide gate and put the caps back on.
2006 23B Hybrid with 10k round bar WDH
2011 F150 4x4 SCREW Ecoboost, Max Tow, Integrated TBC, 3.73 LS axle, Firestone Ride Rite airbags.