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Mold Removal in Bathroom

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Question:

How do I remove this mold?

Mold growing on underside of toilet in bathroom.

The mold growth on the underside of the toilet tank is due to condensation.  This occurs warm, humid air in the bathroom interacts with the cool surface of the toilet tank.  The more often the toilet is flushed, the more condensation you’ll see.

This can be prevented by running the bathroom fan more often.  Ideally, replace the fan with a Panasonic WhisperGreen model.  If you already have a working fan, consider installing a programmable timer switch.

The mold can be cleaned by scrubbing the area with a borax/water solution.  If the area is cleaned regularly, mold growth is unlikely to reoccur, even if you continue to see condensation.

Question:

What could be causing this? It is not a roof leak and we recently replaced the fan bc we thought it wasn’t working well enough any longer.

Mold on bathroom ceiling

Broad, sporadic growth like this is typically due to condensation.  This can be caused by an ineffective/under utilized exhaust fan or missing insulation above the ceiling.  Try running the fan 24/7 and see if the mold stops.  At a minimum, run it for 1 hour after each usage of the shower. Note – the existing growth will not fade away with time, you’ll need to clean and repaint the ceiling.  I recommend using a high quality exterior grade paint.  These contain mildicides that help inhibit mold growth.