Determine the location of the toilet, the water intake connection and the black water tank connection. Once these items are located, see if they can remain in the same place if the toilet is rotated 90 degrees. Sometimes the connections must be moved.
Measure the RV toilet and see if there is enough room to rotate it 90 degrees in either direction. The toilet is longer from front to back than it is from side to side. There may not be enough space to turn the toilet. Many times the shower or sink are right up against the toilet unit.
Rotating the RV toilet 90 degrees may require moving other major bathroom components such as the shower, tub or sink. The water supply and connections to black water and gray water tanks may need to be moved or reconfigured in order to accommodate the new position of the RV toilet, sink and shower.