RV Repair: no fuss flush, black tank, shower drain

Question
I have a 2004 Keystone Everest The black tank flush  sprays water up under the shower ? when I turn the water on. It worked fine a few weeks ago so something is broken heres the problem when I follow the water line in from the flush hook up the line goes to an elbow then the line goes up into the hole for the shower lines. When  I turn the water on it leaks from up there. I can t see in the hole and have no idea why the line would be running up there. there are four lines going into the shower access cutout and four returning to the hole in the floor to the hole tanks. Could they have just stuck extra length of line up into that hole? making a loop? any ideas would be appreciated

Answer
Hi Kelsey:
Most likely the problem is that the head of the flush system where it goes into the blackwater is plugged up with stuff. You need to find where it goes into the tank, take it out and clean it. Those flush system plug up a lot unless you use it everytime you dump. I have no idea why they would run a line to the shower drain. Maybe a vent? I would call Keystone tech services and ask. Sounds a little strange to me. Sorry I could not be of more help.
Bill