Home>Discussions>BATHROOMS>Bathroom vent fan drips, but the usuals fixes don't work.
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gail66
Bathroom vent fan drips, but the usuals fixes don't work.
gail66

Leaking bathroom fan...nothing fixes it!!!
We have installed a new Nutone 80 cfm bathroom fan in our 7'x10' bathroom. We used solid ducting to vent it out the roof with an flappered roof vent made for bathroom fans. We started with a 90 degree elbow, added about 2' of straight ducting and then used about a 30 degree turn to hook into the roof vent. All seams were taped shut. There are two doors to the room. One door has about .25" gap under it and the other has about .5" gap.

The first time we used it, it dripped onto the floor after 5 minutes in the shower. It only drips when we run the shower.
1. We thought there wasn't enough insulation, so we added more blown-in insulation on top and throughout our attic. We insulated the ducting and the housing (10" on top of the housing), R-7 around the ducting. Its about 55 degrees today, but it doesn't seem to make a difference how cold or hot the temperature is outside. Still drips! We removed the blower assembly to see that water was collecting on the top and side of the housing, running down the sides (including over the electric plugs) and onto the floor. It was actually fairly dry inside the ducting.
2. So, we got a 110cfm assembly to go into the same housing, as suggested by the manufacturer. 5 minutes, still drips.
3. So, we tested the circuits. 120 volts feeding the motor. We had a timer switch on it, so I changed it to a regular light switch. 5 minutes, still drips.
4. I took the flapper off the roof vent. 5 minutes, still leaks.
5. There is really no room to reroute the ducting as the roof vent sits just down from the pony support wall top plate and stud (It's literally backed into a corner).

I am at a loss...do you think one elbow at the beginning would slow it down enough to back it up like that and make all the moisture condense in the housing or am I, and everyone I have talked to so far, missing something?

Please help!

dj1
Re: Bathroom vent fan drips, but the usuals fixes don't work.
dj1

Quote: "do you think one elbow at the beginning would slow it down enough to back it up like that and make all the moisture condense in the housing or am I, and everyone I have talked to so far, missing something?"

Could be. Check your code in regard to venting.

How long is the section of vent that rises at 30 degrees?

bill
Re: Bathroom vent fan drips, but the usuals fixes don't work.
bill

also check to see if your house has a negative air pressure. what this means if the kitchen exhaust. chimney exhaust, dryer exhaust etc all run and there is no fresh air intake then your house has a negative pressure and the exhaust fan can not over come this negative pressure. . Try to open up a window in the bathroom or other room and then run the shower with the exhaust fan running to see if this makes a difference. if it does then you need a fresh air intake.

Fencepost
Re: Bathroom vent fan drips, but the usuals fixes don't work.
Fencepost

Your description indicates to me that the airflow is totally blocked.

There should be a damper at the exit of the fan housing, where the duct attaches. Remove the blower from the housing, and check to see that the damper flaps freely, with the larger part swinging into the duct. If it is stiff or doesn't open, that's your problem. You may have inadvertently blocked the damper or distorted the fitting when you installed the duct. The damper may have been incorrectly installed in the factory. Duct seal tape on the outside of the fitting can interfere with the damper's hinge pins, which usually poke through the housing.

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