If your bathroom is under an attic space, check for any pipes running through the attic. If there's HVAC equipment up there, have an hvac contractor examine the unit and its service lines carefully. A clogged condensate drain or overflowing pan could drip water onto the bathroom ceiling from above. Ruling out those potential causes, we arrive at something you've probably already thought of: a roof leak. The question is, Where exactly is the roof leaking? It's not likely to be directly above where it's showing up on your ceiling. Look for water marks on the underside of the roof sheathing and/or rafters or truss members. Water getting through the roofing can travel downwards and sideways for significant distances before it drops to the attic floor (your bathroom ceiling) below. Any roof penetration, such as a plumbing vent, skylight or chimney, above the bathroom leak site is a potential suspect.
Vent Fan Leakage
So let's assume you do have a vent fan, and the duct runs up through a cold attic space. Water vapor in the vented air can condense as it travel through the ductwork, causing water droplets to drip or run back down the duct and ultimately onto your bathroom ceiling and/or floor. If this is the case, should you still use the fan? Absolutely. In fact, you should use it more often and run it for longer periods to help dry out the duct each time. Run the fan during and for 20 to 30 minutes after each shower. Also, make sure the duct is insulated and that the flapper on the outdoor vent cap operates properly. If you have crummy slinky-style flexible plastic ducting, consider replacing it with smooth, rigid metal, which is better at ejecting the moist air and won't collect condensate like flexible duct can. If you try all of these fixes and the problem persists, you may need to reconfigure the duct run so the majority of the duct slopes toward the exit vent.
Philip schmidt writes for Networx.com.View original post.