condensation on vent

Old 07-12-14, 07:54 PM
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condensation on vent

There was condensation on the air vent in our bathroom. It's in the ceiling, and we haven't used that bathroom for two days, so we know it's not from a hot shower.

Could this be caused by a clogged condensate drain?

Thanks in advance!
Old 07-12-14, 08:33 PM
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This is possible if the clogged drain is directly above the bathroom vent.

I usually find that this is caused by outside air running backwards and entering the bathroom from outside. I usually seal the box to the ceiling (not the grill) and install a 5C523 backdraft damper in the 4 inch aluminum flex duct from the exhaust fan.

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