My Canyon Trail Y27FRES Fifth wheel has the same issue, kitchen sink and toilet share a 40 gallon tank, while my shower and bathroom sink share an 80 gallon tank...
But, the kitchen sink is on the lower living level, while the toilet is on the upper bedroom area, so the bottom of the toilet is on nearly the same plain as the sink trap...
How poor of a design is this from a sanitary and water volume perspective?
