This is very simple but frustrating to search for. I wasn't sure how the drain worked on my 1975
Trillium and didn't want to experiment just before heading out camping. Finally found the time to look into it. The water travels from a tube attached to the sink right out to the "drain" outlet you see outside the trailer. There is no holding tank. You'll want an old piece of garden hose and a jug, or run the hose to a drain on your site if it has one. Here's a video tutorial I prepared for other newbies (like me):