Water Dripping From a Bathroom Exhaust Fan?

Seeing water drip out of a bathroom exhaust fan is alarming for a pretty obvious reason: there is water coming out of your ceiling. A roof leak is certainly possible, but during cold weather there is another common explanation—condensation.

Warm, wet air meets a cold duct

A shower produces warm, moisture-filled air. The exhaust fan pulls that air into its duct on the way outside. If the duct passes through a cold attic or other unconditioned space and is not properly insulated, the moisture can condense on the cold interior surface.

Enough condensation can collect and run back toward the fan, eventually appearing as a drip in the bathroom.

The duct route matters

The exhaust duct should terminate outdoors and should be installed and insulated appropriately for the conditions it passes through. Poor routing, low spots and unnecessary bends can make moisture problems worse.

Because attics can contain electrical wiring, fragile ceiling surfaces and difficult footing, this is also one of those situations where “I watched a video” is not necessarily the same thing as “I should crawl around up there.” If access is difficult or you are unsure what you are seeing, call someone qualified.

Don’t assume

Water at a fan can also come from an actual roof or exterior leak, so condensation should not simply be assumed. The important thing is to trace the source. A properly installed bathroom ventilation system should remove moisture from the house—not bring it back into the bathroom.