HI Helena and welcome to the forum. I have a 2010 and they may be similar. To get to the tank I remove the carpet and the plywood cover. The tank sits in a molded well below the plywood. Facing the rear of the trailer, the connections, two as I recall are on the right. One is the breather and the second is the drain. A tee in the drain line goes to the water pump. Tight quarters and
fiberglass splinters make working on it difficult . Be aware that the tank is made of HDPE (milk jug plastic) and is difficult if not impossible repair. There is a chance the drain line fitting is loose. I had trouble with mine. Hope that helps. Raz