Ok thanks, was just wondering if we were talking about the same thing. Really odd problem. Do check your showers, both inside and out as others have suggested. I never heard that before but apparently it has happened. We'll get this figured out yet.

so the drain is located directly under the kitchen sink area towards the back part of the camper. There are 2 drains one is the overflow and then the fresh water drain. just a small screw on /off cap