Suggestions, re-installation of sewer tank Y fitting/valves

Steve,
I am having a similar issue on Fuzion (form what you describe I have same setup black and grey plumbed into Y fitting all glued together), but I can't even remove the valve. How far away did you push the whole Y assembly (grey and black) to remove the valve. I got about 1/4" opening but it seems like it is stuck on something. To get to this opening I had to remove the screws from grey tank also.