The answer to 'why is my dryer vent water damage' is that a clogged or obstructed dryer vent is the most common cause. When the dryer vent becomes blocked, moist hot air from the dryer can't properly vent outside, causing condensation and water buildup in the vent. This can lead to water damage, mold, and other issues.
Some other potential causes include a damaged or cracked vent hose, a vent that is too long or has too many bends, or a vent that is not properly sealed or insulated. Symptoms of dryer vent water damage can include damp spots on the wall, musty odors, and excess moisture buildup around the dryer.