I have a 2012 Winnebago 35F which does not come standard with a Black Tank Flushing/Cleaning system. My research indicates that there are aftermarket systems which can be installed in the Black tank with a flushing port in the Sewer/Water Bay. Anyone have any experience with these types of systems. Apparently you hook up a water hose and then it sprays using a spinning turbo type device installed on and in the Black Tank to rinse the interior of the Tank. Approximate install cost including the spray head is $125.00