Hi Dave,
I had the same problem a bunch of years ago. I used a hole saw to saw a hole near the bottom (probably 3 or 4 inches from the bottom) of the wall in the shower that faces forward. That gave me easy access to the hose and the hose clamp.
I bought a Beckson water proof Screw-Out inspection Plate to finish the hole and to allow future easy access. They have them at Defender. I won't get up to my boat for a week or two, but when I do I'll send you a picture.
I just had to tighten the hose clamp to fix my problem.
Hi Dave,
Here is the picture of the access point to the holding tank, hose and the hose clamp that I installed.