After showers the condensation in the duct from my bathroom fan drips back into the room. I have a fan timer and we've been running it for 30-45 minutes after showers. The fan is old with a regular bladed fan (not one of those squirrel cages). The duct is PVC pipe running horizontal along the attic floor for about 10 feet until it turns up to go to the roof vent. Any suggestions?