It's possible to find condensation in the dryer drum after the drying cycle ends. Condensation usually results from improper ventilation, which can cause moisture and lint to collect in the dryer's exhaust system duct and leak back into the dryer after it turns off.
Generates Moist, Hot Air Emissions
Your dryer naturally produces moisture as hot air combines with wet clothes in the drum, but the moisture eventually filters out the exhaust system. However, an obstruction in the exhaust system can cause moisture to build up in the duct and drain back into the dryer. One way to keep your dryer from producing moisture is to periodically clean its exhaust system. Whirlpool recommends that you clean the entire exhaust system once every two years and more frequently if you run your dryer a lot. If you're uncertain how to do this, review the manual for your dryer. Or purchase an exhaust system cleaning kit. In addition, empty your dryer's lint screen at the end of each drying cycle. If the screen becomes filled, more lint will end up in the exhaust system, which can cause a block.
Improper Ducting Materials
The material used for the duct could contribute to your dryer producing condensation. If your duct is made of plastic, it's more susceptible to moisture than metal ductwork. As moisture builds inside a plastic duct, it combines with lint in the air to make a gummy paste that blocks airflow. Eventually, the paste restricts air circulation, and moisture drips into the dryer. Change out plastic ductwork for one made of a heavy duty metal. Also, choose a metal duct without ribbing to prevent moisture from becoming trapped in its ribs.
Ducting Isn't Straight or Supported
A dryer will generate moisture while it's running if its duct isn't straight or supported, which creates poor air circulation. If the ducting bows or bends, airflow is constrained in these areas, making it more likely for a blockage to form. Review any kinks in the duct either by cutting it or changing its configuration. Use aluminum foil tape instead of screws to secure it in place; screws can trap moisture causing condensation to pool inside the duct and drain into the dryer.
Ducting Is Too Long: Hot Air Can't Dispel Quickly
A long duct takes longer for a dryer to expel moist, hot air, and as a result a dryer is more apt to accrue a lot of moisture. The vent duct should never be longer than 25 feet so the dryer's exhaust is discharged properly. Although 25 feet is the maximum length for a duct, improve airflow and reduce moisture by shortening the duct length. Take care when shortening it to ensure the duct is straight and horizontal to aid air circulation. Eliminate bends in the duct whenever possible. Consult a dryer specialist if the duct is near, at, or longer than 25 feet for guidance. He might recommend that you install a blower fan to improve air circulation, which should also reduce the chance of finding moisture in the dryer.