Bad Experience on First Outing 6504 Black Tank

[Excella]

My wife and I have been RV'ers since the late nineties and have owned eleven rv's including three class A's, three fifth wheels and we just bought our fifth travel trailer
Our first outing in our "New To Us" 2014 The Vibe 6504 was a two day stay in a park about an hour from our home. Everything went well until we were leaving the park and stopped at the dump station and opening the valve on the black tank resulted in a no go situation. I always hold the waste hose when I open the valve to feel the flow and I felt nothing. The handle moved extremely easily so it was my suspicion that the handle was disconnected from the blade in the valve so I drained the two gray tanks and went home. I ordered a replacement valve from Amazon and pondered my next move. I researched how to deal with a disconnected valve handle and discovered that I can cut off most of the plastic and pinch the valve and pull it open with pliers. Before cutting anything, I placed a plastic storage bin under the valve and gently pulled the handle and looked inside the outlet and could see the valve was moving? Extensive research on Google said that I probably have a "Poop Pyramid" I have a connection for a "Black Tank Flush" so I hooked a hose to it and when I tuned on the water things sounded strange so I turned it off and checked in the trailer and opening the toilet valve gave me a spitting fountain that came up 3/4 of the bowl.Over the next couple of days I tried everything that Google said and even some ideas that my neighbors had including hot water up the 3 inch drain, 2 different size plumbers snakes, chemicals in the toilet after using my wet dry vac to empty as much as I could. I even ordered a camera from Amazon to run up the drain but couldn't figure out what I saw. I made up a angled spray fitting for the end of my hose and shot hot water against the obstruction and all that did was make my valve hard to operate when the lubricant washed away. (Silicone lubricant spray fixed that.) I made up a fitting for my wet dry vac and tried sucking out the obstruction and when that didn't work I changed it around and tried blowing up the drain My neighbor suggested I rent a steamer! I saw a toilet auger online at Home Depot in two sizes, six and three feet so I figured I should measure the distance from the toilet opening to the tank outlet to see what size was best for my situation, so I calculated where the opening was and got my garage creeper and got under the trailer on the door side of the trailer and there, at the tank, buried up inside the frame and not visible from the other side of the trailer where I was working for 3 days was another (insert expletive) DUMP VALVE. While searching for a solution I had come across a post from a guy with the same symptoms as mine and an experienced R'ver told him that there is only one dump valve on a line. Who would have thought???

[5picker]

Sorry for your troubles.

Is it possible someone added a screw on termination valve to the end of the sewer port that you mistook for the black tank valve. If your grey comes out the same port then I wouldn't think you made that mistake that but if the gray has a separate port (as mind does) then maybe.

[Excella]

My 6504 has three waste tanks, two gray and one black. Three valves are on the left side of the trailer, two gray 1 1/2" valves and a black tank drain valve that is 3". At the lower end of my black waste tank underneath my trailer there is another 3" valve right at the tank. I can see the three valves on the left side where I connect the sewer hose while standing erect however I have to get down on my hands and knees on the opposite side of the trailer to see the hidden 3" waste valve. I have used the screw on valve that you sent a picture of when I fulltimed in a 40 ft. fifth wheel that had two black and two gray waste tanks and I was able to extend my stay at a place without sewer by closing that valve and opening the two gray tanks thereby sharing the volume of the two gray tanks.