The shower uses a patent pending drain design that allows water to drain into an angled gutter and exit through an included 1.5" threaded marine shower drain, even when the van is parked on a moderate slope. The drain hole must be be drilled through the floor of your van, directly underneath the center of the shower's gutter. Most people choose to hook up their shower drain to the same place the rest of the gray water in their van drains - either a gray water tank or directly out of the bottom of the van onto the ground.