Leak when flushing black water tank

[Road Dog]

When we picked up our 2016 Classic last Janurary, it was winterized and we left it that way until we went to Florida the 1st of Feburary.
The first time we hooked up the black water flush it poured water. Not knowing what the problem might be I didn't try it again. I used a hose directly into the toilet until I got the leak fixed.
I made an appointment at Jackson Center and they discovered that a hose was loose, they fixed the problem and we were on our way. Worked great after that.

[Roadroamin]

I have a 2011 27 FB with a busted back flow prevent valve, cheap is right but only in quality. I got a price from the Airstream dealer in Canada, CAD $ 102. I will replace it with an elbow as well. It is accessible from inside the closet where there is a panel that is held in place by 5 or 6 phillips screws.