We have a 2011 Elkridge 5th wheel, which we bought in May of this year from a couple who had only used it twice. It is probably a good job that they did only use it twice because this weekend we discovered that our black tank was also clogged up and it would only let liquid out and no solids. My husband bought a snake and tried that, not much luck, he tried flushing, no luck there either. Things got a little more drastic after that, he removed the valve, had to cut the pipe, armed himself with a flashlight and mirror and managed to look inside the black water tank. You'll never guess what he found! The piece of plastic that Heartland drill out of the black water tank when they are fitting the pipes had fallen into the black tank and had lodged itself behind the valve, completely blocking the valve so no solids could come through. He managed to get it out, then he had to drain the tank. He put a tarp down and the next thing you know everything came out and he was covered yuk! We flushed with gallons of water until everything came out and was completely clean. Then he had to replace the valve and repair the pipe. We are lucky that he was able to do this himself or it would have cost us hundreds of dollars instead of the price of a snake and a new pair of coveralls. We live in our 5th wheel full-time so it would also have been inconvenient to have to up sticks and go to a dealer to get this fixed. I'm not sure if this is a big problem with Heartland or a one off, but it's certainly something that should be noted and may be the root of your problem too.