I have a Catalina 1995 Catalina 30. I believe that the holding tank is original but not sure. For the past month when I have gone on the boat after a few days there is dirty water from the head in the bilge. I have checked all the hoses and haven't found a leak. I have followed for the aft of the tank through the engine compartment and no signs on a trail. And it only seems to appear after sitting on the mooring for a few days.