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Mold in the toilet

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Toilet mold growth.  

Lovely topic.  Thankfully, as unpleasant as this topic may sound, toilet mold growth is a fairly uncommon occurrence.  If toilet mold growth is the worst of your bathroom mold problems, you're doing pretty well. First, let's divide this into three main categories.  This list is ordered from least common to most common. 

1.  Mold growth on the toilet.

2.  Mold growth on the adjacent wall.

3.  Mold growth in the floor beneath the toilet.

Mold growth on the toilet.

Mold growth on toilet

First, let's look at the material itself.  The vast majority of toilets are constructed from porcelain, a durable, non-staining, non-porous material.  These qualities not only make the material perfect for handling life's biological unpleasantries, they also make the material highly resistant to mold growth.  Due to this, mold growth on toilets is unusual.  For growth to occur, it must find another food source - settled dust.  Often invisible to the naked eye, a thin layer of dust settles upon every surface of a home, including vertical and even inverted surfaces.  This microscopic layer of dust provides sufficient organic material to propagate mold growth.  

Remember, mold growth requires both a food source and available moisture.  Just because the settled dust has provided a food source does not necessarily mean that mold growth will inevitably follow.  Moisture must be present as well.  On a toilet this primarily occurs through condensation.  When the shower is used, warm, humid air is introduced into the environment.  This moisture laden air hits the cold toilet (cooled by the water) and condenses. If the condensation is severe, drips will form and damage the floor below.  

Cleanup?

Good news.  Because porcelain is designed for easy cleanup, mold is readily removed from the surface. Standard toilet cleaner should remove any accumulated mold growth and staining. 

Mold growth on the adjacent wall.

Toilet mold problems

The same interactions that cause moisture and mold growth on toilets can also lead to mold growth on the adjacent wall.  Typically this occurs when the cold surface temperature of the toilet cools the temperature of the wall directly behind the toilet.  Once the wall temperature drops below the dew point, moisture condenses and mold growth ensues.

Cleanup?

Not easy.  If mold growth occurs on the wall, it is because the distance between the wall and the toilet is very small.  Often the distance is less than 1”, leaving little room to insert a scrub brush, rag or other cleaning utensil.  A tooth brush can work well, but as one can imagine, the work is tedious. In cases with severe mold, the toilet must be removed to provide access.

Mold growth in the bathroom floor beneath the toilet.

Condensation from toilet leading to mold problems.

Mold and moisture problems can effect the bathroom floor through two avenues.  First, if condensation is severe, water will drip from the holding tank and saturate the floor.  The level of damage, if any, depends entirely on the flooring material.  Well sealed tile will withstand constant water exposure.  Hardwood or laminate flooring will fail relatively quickly.

Cleanup?

Light mold growth can be removed with floor cleaner.  Significant damage must be addressed by a professional, as floor removal will likely be necessary.

How to prevent toilet mold growth.

In all three cases described above, condensation is the primary cause of mold growth.  Thus, prevention must hinge upon preventing or lowering the condensation.  If you have a working bathroom fan already installed, the solution is simple.  Run the fan.  If necessary, a push button timer with 20, 40, 60 minute increments can help ensure proper ventilation occurs.  Bathroom fans often lack sufficient power.  You’ll know this if you’re still seeing condensation even when running the fan for 60 minutes after each shower usage.  Time for an upgrade. 

If your bathroom does not have a fan currently installed, your options are much more limited.  Opening the window can help, but this isn’t comfortable in January.  And realistically, most people won’t keep the window open long enough to achieve proper ventilation rates.  The solution?  Install a bathroom fan.

RECENT MOLD INSPECTIONS RELATED TO BATHROOM TOILETS 

Reason for inspection:

  • Leaking from the toilet in the unit above has caused water damage and mold growth on the bathroom ceiling.

Summary of concerns:

  • Visible mold growth noted on back side of sheetrock ceiling in bathroom.
  • Increased moisture content was noted in affected sections of sheetrock.
  • Plumber had resolved leakage prior to inspection.

Summary of recommendations:

Remediate mold growth and water damage:

  • Establish containment
  • Install HEPA scrubber for negative pressurization throughout the duration of work.
  • Remove all affected sheetrock from ceiling (approximately 60% of the bathroom or 30 square feet)
  • Remove any underlying insulation that had been affected.
  • Clean/treat/encapsulate any remaining stained framing.
  • Perform detailed HEPA vacuuming of the entire contained area.
  • Apply EPA-registered anti-microbial agents to the entire contained area via ULV fogger.

PROPERTY DESCRIPTION:

  • Condo unit located in Seattle, WA.

Hall Bathroom:

Summary:  Abnormal Conditions Found!

Observations:

  • Section of sheetrock ceiling had been removed by plumber to access the area of leakage.
  • Increased moisture content was noted in sheetrock around the hole.
  • Increased moisture content was noted in small section of sheetrock over tub.
  • Visible mold growth was noted on visible areas of back side of ceiling sheetrock.
  • Subfloor above is constructed of concrete and did not show signs of damage.
  • No increased moisture content noted in testable areas of framing.
  • RH:51.3% Temp:67.4°F CO2:544ppm CO:0ppm

Recommendations:

  • Establish containment
  • Install HEPA scrubber for negative pressurization throughout the duration of work.
  • Remove all affected sheetrock from ceiling (approximately 60% of the bathroom or 30 square feet)
  • Remove any underlying insulation that had been affected.
  • Clean/treat/encapsulate any remaining stained framing.
  • Perform detailed HEPA vacuuming of the entire contained area.
  • Apply EPA-registered anti-microbial agents to the entire contained area via ULV fogger.
  • Mold growth bathroom toilet
    Mold on wall behind toilet
  • Damage from toilet condensation
    Damage due to toilet condensation
  • Light mold growth in toilet
    Light mold growth occurring in toilet
  • Toilet mold
    Mold growth on underside of toilet. Also, note the mold growth occurring on the wall adjacent to the toilet