Just making sure I am correct o this - The secondary drain plug should be unplugged and plumbed so it is draining into the pan below. There is rust in the pan and it appears that the primary had backed up and draining out where ever out of the bottom of the unit.
From what I can see in your photo, I think you have it right. The plug almost looks like it’s a one-way valve plug, that should let water out. It looks a little high off the bottom to be effective. ?? Do you have any more photos?
