Why Is My Bathroom Exhaust Fan Dripping Water?
Dripping after showers, especially in cold weather, usually points to condensation inside the exhaust duct. Dripping during or after rain points more strongly to an exterior vent, cap, flashing, or seal leak. Water reaching electrical parts requires immediate shutdown and qualified inspection.
What to know
- The timing of the leak is the fastest way to separate likely condensation from rain intrusion.
- Uninsulated, sagging, crushed, long, or poorly sloped ducts can collect condensation and send it back toward the fan.
- Persistent water near the fan’s wiring, light, switch, or ceiling structure is not a routine do-it-yourself cleaning issue.
A bathroom exhaust fan commonly drips because warm, humid bathroom air condenses inside a cold or poorly insulated exhaust duct. Another possibility is rainwater entering around a roof or wall vent.
Pay attention to when the drip occurs:
- After showers, especially in cold weather: condensation is more likely.
- During or after rain: an exterior cap, flashing, or seal may be leaking.
- During both: the system may have more than one defect.
Broan-NuTone identifies condensation from cold or improperly installed ductwork and leakage around the wall or roof vent as principal causes of water appearing at a bathroom fan. [1]
Treat water and electricity seriously
Do not touch a wet fan housing, light socket, switch, or exposed wiring.
Stop using the fan and seek qualified help if water is flowing through the electrical housing, the breaker or ground-fault device trips, the fan buzzes or sparks, a burning odor appears, the ceiling is sagging, or the leak is substantial and unexplained.
A renter should document the leak and notify the property owner or manager promptly. Do not climb into an attic or onto a roof without authorization, safe access, and appropriate equipment.
Cause 1: condensation inside the duct
A shower sends warm, moisture-rich air through the exhaust duct. If the duct passes through a cold attic, wall cavity, or roof space, water vapor can condense on the duct’s interior.
The problem becomes more likely when the duct is:
- uninsulated in a cold space;
- excessively long;
- crushed, kinked, or sagging;
- sloped back toward the fan;
- partly blocked;
- leaking air at joints;
- connected to a poorly functioning exterior damper.
Condensation can collect until it runs back through the fan grille. Broan-NuTone recommends insulated ductwork and proper routing, and notes that a duct terminating through a wall should be arranged so moisture does not drain back toward the fan. [1]
Cause 2: a roof or wall vent leak
Water that appears during rain may enter through damaged roof-cap flashing, failed sealant, a cracked wall cap, missing siding details, a damaged damper, or wind-driven rain entering a poorly designed termination.
An exterior leak may wet insulation, framing, or ceiling material before becoming visible through the fan opening. Repair may require a roofer, siding contractor, HVAC technician, or electrician, depending on where the water enters and what it has reached.
Cause 3: insufficient fan runtime or airflow
A fan that stops immediately when the shower ends may leave humid air in the room and duct. Broan-NuTone recommends operating a bathroom exhaust fan during the shower and for roughly 20 minutes afterward. That is general guidance, not a universal timer setting for every room or climate. [2]
Poor airflow can also result from a dirty grille, a stuck exterior damper, a disconnected duct, an undersized or failing fan, a tightly sealed bathroom door with inadequate make-up air, or a duct that terminates in an attic instead of outdoors.
The fan should discharge outside, not into an attic, crawlspace, or wall cavity.
What you can inspect safely
Without opening electrical components:
- Note whether dripping follows showers, rain, or both.
- Clean dust from the removable grille according to the manual.
- Hold a sheet of toilet paper near the grille to see whether the operating fan draws air.
- Check whether the exterior damper opens, but only from a safe ground-level location.
- Photograph stains and record the weather and shower timing.
- Ask a qualified person to inspect duct insulation, joints, slope, and termination.
The toilet-paper check is only a crude airflow indicator. It cannot measure whether the fan meets its rated airflow or whether the duct is correctly installed.
The repair depends on the cause
For duct condensation, a qualified repair may involve insulating the duct, sealing joints, replacing crushed flexible duct, shortening unnecessary runs, correcting low spots, directing slope toward the exterior where permitted, or improving fan runtime and capacity.
For exterior leakage, the repair may involve replacing the wall or roof cap, repairing flashing, sealing the penetration correctly, restoring damaged roofing or siding, or replacing wet insulation and ceiling material.
Caulk smeared onto the interior grille does not solve either problem. It merely hides the exit chosen by the water, which is less a repair than a bureaucratic reassignment.
Bottom line
Dripping after showers and during cold weather points toward duct condensation. Dripping during rain points toward an exterior vent or flashing leak. Because the fan contains electricity and the duct may pass through concealed building spaces, persistent water should be inspected rather than repeatedly wiped away.
Limits and cautions
- Timing suggests a cause but does not prove it; some systems have both condensation and exterior leakage.
- The article does not provide roof-access, rewiring, or concealed-duct repair instructions.
- Fan airflow, duct routing, and code requirements vary by building and jurisdiction.
Source notes
- Bath and Exhaust Ventilation Fan FAQsBroan-NuTone
- Controlling Moisture in the HomeBroan-NuTone
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