One type is the 25mm waste - straight or angle. These are defined for each sink or basin that uses them. They are made of two sections -one piece fits from the top and requires a small smear of silicone under the lip to prevent leaks. The bottom section screws, by hand, from underneath.

The black 28mm ID corrugated hose makes an ideal internal drain hose, as it keeps it cross section while allowing tight turns. It doesn't matter if it curves up and down before exiting the floor, as it can act as an S-Trap to prevent foul air rising up the pipe.

Access to remove and unblock should be provided. Use a suitable hose clamp at the top. A simple 25mm PVC joiner can be used under the RV for connecting additional length at the Caravan Park.