I have just discovered that my patio door is leaking. It is a French door style patio door, but only one side opens. Please refer to the attached pictures. The water seems to be coming in from the side that doesn't open, and draining under the floor (between the hardwood and the subfloor), and then leaking down the air vent. I'm not sure if the water is penetrating the door that doesn't open, or if it is getting underneath the door that does open and flowing under the other door. How would I go about determining the cause of the leak? Any help with this issue would be greatly appreciated.