At PDI salesman told me that the rear bathroom holding tank was a combo black/grey for the garage bath. Also from other posts here seems that's what others have as well. Tank level gauge has never worked in that bathroom so on this, our final trip I decided to fill the tank to top and flush it good. Ran bah faucet for 30 min and gauge still showed empty soi figure gauge is def broke, no big deal. Just as I'm about to shut off water wife yells that the kitchen sink is filling up. Another test and its confirmed, my rear bath holding tank is a black only, grey water goes to galley grey tank. Did I miss something and everybody's is like this or did I just get the special one.