I bought a replacement cap for the large back-up drain with a standard hose fitting. I carry a gray hose for use in a park when we will be there for several days. Hook up the hose to the drain fitting, open the gray tank and have the hose placed in campground sewer drain. There is also a fitting to hook the hose to that fits in the drain to it covered and sealed as required by some areas. Never need to worry about over filling your tank. If you are going to need to dump the black tank, close the gray tank a day early to build up some gray for flushing the macerator system and disconnect the hose and recap the fitting prior to dumping.
Bob
