On my unit there was an anti-siphin thing up in behind the shower that was in the line between the outside hookup and the black tank.
It got clogged so I took it out and put a inlet on the outside that had a back flow preventer in it.
The thing that I am refering to has hose clamps on it, so it is possable that your leak is on it. I found it impossible(short of tearing out the steps or cutting a hole in the floor) to get to the top of the black tank where the flush sprayer is hooked to the hose.
To get to mine I had to take the drawers out of the pantry and there is an access panel in the pantry that comes off and it give me access to the rear of the shower fixture and the anti-siphin thing that I am talking about.
Good luck...I hope this helps you..
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