Black Tank Flush

[VTSweetpea]

My husband just finished dealing with a clog in our flush system. The system had worked fine until we got back from our last trip. When he went to do a final tank flush prior to winterizing the RV, water started leaking out from under the rear of the RV and soaked the interior of the "trunk" (storage area behind the spare tire). He found that the leak came from the vacuum breaker device that's installed on the flush system. The function of this device is to prevent a vacuum ( as might occur if there was a sudden drop of water pressure while using the flush) and potentially sucking the contents of the black water tank back into the freshwater system.
When he removed the VB and took it apart, he discovered that it was clogged with debris. He cleaned it out and put it back together, then reinstalled.
You might want to check this device as the possible cause of your clog. It does come out easily as it installed with two threading plastic fittings.

[Blue~Go]

Aha. Good info. I'm going to guess that's at/in-with the last threaded fitting (hand tightener type) that you can see in my photos just before the tank.

[Chinookers]

Yes I use the black tank SaniFlush most of the time when dumping tanks.

I also periodically use a tank wand down the toilet.

Every three years or so I get both black and gray tanks professionally cleaned (http://allprowaterflow.com/) - it's amazing how much gunk and calcium deposits the professional gets out using 3000PSI.

[Blue~Go]

...it's amazing how much gunk and calcium deposits the professional gets out using 3000PSI.

I'm surprised that wouldn't just blast through the tanks or the rubber collar on top. But I guess it doesn't since you've successfully had it done a number of times. Or maybe that's not as forceful as it sounds. I guess I don't really know, for example, how many psi you get at one of those really powerful wand manual car washes.