I have a 2004 25'Classic with a rear queen bed. I have had trouble the past few times cleaning out the black tank. The rinse feature is not working. I'm working on getting it cleaned, but in the mean time, needed a way to rinse out the tank and have a back up for cleaning it out when it happens again!
What I did to fix this was to put a water connection inside the bathroom with a toilet spray wand with a shut off connected to it. The hose and wand fit great inside that little door that is under the sink at floor level. On the outside of the trailer, open up the door to the refrigerator. On the right side wall drill a 1" hole for the 6' water hose to go through (I got one from HomeDepot for a hose reel connection). Now what you need to do is snake the water hose through so it comes out at the little door opening under the sink. What I did was take a straightened out coat hanger with one end bent back in 180 degrees for the hose to go over and catch and feed it through first from the outside opening till I could see and reach it from the bathroom opening. Doing this might take a few tries, but once you have that lined up, just push the hose in from the outside and gently guide it from the inside with the coat hanger. After you have it in, I put a 90 degree elbow on the outside, with some silicone all around the hose end and pushed it up snug into the opening. I also put a 90 degree elbow on the wand end so the hose is not getting kinked when in use.
One word of caution, MAKE SURE YOU HAVE TIGHTENED UP THE CONNECTIONS ON THE BATHROOM END, before turning on the water!
I'm sure this has been done here before, but I was not able to find it.