The black water hoses some come with the bayonet end in order to hook up several lenghts and an elbow to conect by screwing on to the parks sewer lines, on some older parks all they provide is a staight pipe down and you need to insert the hose at least 2' feet or more in order to prevent the end to "pop" out when you open the valve, I use the blue hoses and have never had a problem, I also have a device looks like a box that straddles the hose and I fill it with water at the campsite when done I use that water to either rince the hoses or the dump site, and some parks requiere you to use a cone shapped dougnut to seal the connection.
Hope it helps a little, we pick a town or area and if we like it we stay a few days or a month, if it is not to ower liking we move on.
navegator