Why is Your Dryer Producing Condensation?

VIA Appliance
March 8, 2022
Dryer Repair

Condensation occurs naturally in the dryer when hot air combines with wet clothes in the drum. If the dryer is working correctly, the moisture is filtered out through the dryer’s exhaust system. However, if there is a problem with the exhaust system, usually a lint blockage, moisture will remain in the dryer.  Other causes of the issue all relate to the exhaust system unless you have a condenser dryer, in which case the condensate pump’s hoses should be checked for blockages to fix the issue.

What causes condensation in the dryer?

Condensation occurs when warm air collides with colder air or cold surfaces. When the dryer runs, the warm air that dries the clothes should be discharged through the dryer ventilation duct outside of the home. However, if the ventilation duct is blocked, the hot air gets trapped and reacts to the cooler vent temperatures, which causes condensation to occur and moisture to be found in the dryer drum. Moisture from wet clothes is also found in the trapped air that the dryer needs to discharge. Furthermore, condensation can occur if the vent does not have a working flapper to let the air out and stop air or moisture from coming in through the vent.

How to resolve the issue?

Clean the ventilation duct

The dryer’s ventilation duct extends from the dryer to the outside of the home. Most manufacturers recommend cleaning the ventilation duct at least once a year to avoid blockages, dryer problems, and fires from starting. Air discharged by the dryer contains moisture, which when combined with lint, can cause a mushy paste to develop and block the ventilation. The ventilation duct can usually be detached from the dryer for cleaning by removing the clamps, metal tape, or screws that secure it to the dryer. With some dryers, a back panel that the dryer hose goes into may need to be removed. If you have a gas dryer, care must be taken not to disturb the gas line too much, as a gas leak can be fatal. Once you have removed the ventilation duct, lint will need to be removed and the duct checked for blockages. Purchasing a dryer vent cleaning kit is the best way to ensure the duct is sufficiently cleaned. A typical vent cleaning kit comes with a lint brush and flexible parts that can be assembled to form a long brush to clean the entire duct.

Make sure the ventilation duct has been installed correctly

An incorrectly installed ventilation duct can also cause condensation to occur in the dryer. For the ventilation duct to work properly, it should be as horizontal and straight as possible so that the air has a clear and efficient pathway to be discharged from the dryer. Turns and bends in a ventilation duct will also often be places where lint and moisture collect to cause a blockage. Dryer ventilation ducts should also be routed through the roof or outside of the home. If your dryer’s ventilation duct goes through an attic or is vented into a garage, you will be more likely to have condensation problems. Dryer ventilation that goes under the house is also more likely to have problems with condensation. Aluminum foil should be used to join sections of the duct, never screws or masking tape, as screws can puncture the ducting, and masking tape falls off sooner rather than later. The ventilation duct should be no longer than 25 feet. However, you should aim for it to be as short as possible to provide the best airflow and to reduce moisture.

What is the duct made of?

Most experts recommend a ventilation duct that is made of rigid or semi-rigid metal, as they provide the best airflow, with less potential for lint buildup and fire risk. Flexible foil ducts are also common; however, they should be avoided if possible, as they impede the airflow and trap lint. If your duct is made of plastic, it will be particularly prone to moisture and lint buildups and should be replaced with a metal duct. If your duct is made of vinyl, it should be replaced immediately as it is a huge fire risk. Lint buildup with poor ducting is one of the most common causes of household fires. A dryer ventilation duct without ribbing is also preferable, as the ribbing is another place where lint and moisture can collect.

Is the dryer ventilation duct insulated?

If the ventilation duct is not insulated, specifically in colder climates, cold air cools the ventilation duct, causing moisture to form when the hot dryer air is introduced. The hot air can also encounter the cold where the ventilation duct exits the home or if parts of the duct are outside the home. Making sure the ventilation duct is insulated may solve the condensation issue.

Does the duct have a defective flap?

Some dryer ventilation ducts have a flap on the end, which when working correctly, opens to allow the hot air out and closes to stop cold air and moisture from coming in when the dryer is not being used. If the flap is defective, it may be causing the condensation issue. If the ventilation duct is equipped with a flap, make sure the flap is working correctly, and replace it if it is defective.

Condensing dryers

Condensing dryers do not require an exhaust vent. Instead, dryer air is circulated between an electric heater and an air-cooled or water-cooled condensing coil. Condenser dryers have a pump that sends water to a collection container. If you are finding condensation in your condensing dryer, the condensate pump may need to be removed to access and clean the hose(s) connected to the pump. If the issue persists, the pump and level switch, which indicates when the water level in the collection container is too high, should be checked to make sure they are working correctly. The collection container should also be checked for cracks that may be allowing moisture to escape.

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