B190 Enthusiasts

I recently purchased a 1990 B190. In pretty nice shape. I tried to fill the water tank through a garden hose, but soon I discovered that the water is going out through what seems like a drain valve. Not sure if it is part of something else, or if I am missing some connection tubes there. Also, not sure how to stop it. Please help. Pics attached.

Open the second door on the side - there should be a valve under the cabinet. It's to drain the tank for the winter, and someone must've left it open.

Thank you That solved it.