Stan,
The fresh air intake varies with the coach year and model, but all intake systems have a design feature to prevent rain water from entering into the air filter paper element. Normally, this feature is designed into the air intake at the exterior body panel. The exterior panel intake will normally have a box inside the intake grill that allows rain to drain to the bottom below the location that the hose attaches to supply air flow to the air filter. In the bottom of this intake box, there is a water drain that in most cases can allow water to inter the intake hose if it is restricted, especially in heavy rain when the engine is operating.
LaMonte,
Rotating the filter may or may not benefit you, depending on the filter height in relation to the exterior air intake, but normally it is not necessary if the intake is properly designed and the water drain is clean. If the exterior intake is above the filter, it will do no good without a drain hole at a low spot in the hose.
Gerald