My 2004 unit has the same drain valve pictured in Rustic Eagle's post, and it is in the side of of fresh water tank. There are also two plastic hoses hanging from the tank, which are overflow tubes. Two other plastic tubes are located at the other end of the trailer, which are low point drain hoses for the interior plumbing. Your drain for the tank has to be at or near the bottom of the tank, so I suggest you just look all the way around it near the bottom, and you are bound to find it. Hope this helps.