The 14 x 14 inch gasket should be in place to keep water from getting back into the trailer...
You would want any and all water that gets inside the roof mounted housing from its vents etc to freely flow away from the air conditioner unit... We always like to park with alittle tilt to the backside of the trailer just to keep the air conditioner roof drain to go in that direction in lieu coming down on the patio side...
Typical Air Conditioner Install Diagram... Note the large Roof gasket position...
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Roy ken
