Killing and Removing Mold and Mildew from Under Our Leaking Sink

In the previous post, I described how a leaking faucet had soaked the cabinet below the sink and we could see mold growing. I had to remove the sink to see how bad the mold and mildew problem was. No mold is good, but it could have been worse. The mold only covered a small area on the back edge of the counter top, along the edge of the cut-out for the sink.

how to remove black mold from house sink

Exposed black mold growing along the fiberboard and laminate after removing leaking sink.

My first task was to determine how to get rid of the mold. I had heard all kinds of horror stories about how dangerous mold could be, so I waited until I was the only person that was going to be in the house all week to fix the problem. Since I had only heard stories and did not know any facts, I learned all I could about killing and cleaning up the mold and how to stay safe while I was doing it.

The first part of this post includes the steps that I took to kill and cleanup the mold growing under our sink, in case you just want to see the steps I took and the results. If you want to see a summary of all the information I found about the health effects from mold, other cleaning methods for mold removal and methods to prevent mold from growing in the first place, those are provided in our how to remove mold article.

Cleanup and Removal of Mold

When mold is growing in our homes, we have two issues. The most obvious is real damage is being done to the building materials and if not corrected our homes will deteriorate, the second issues is the potential health hazard caused by mold spores.  I cover the potential health hazards later in the post, so let’s assume for the moment that we want to breath as few mold spores as possible.

Our immediate goals were to:

  • Stop mold growth
  • Stop production of mold spores
  • Stop the damage to the counter top
  • Prevent future mold growth
  • Contain or control the mold spores already produced

Luckily, the best way to meet four of the five goals above is to start drying the area immediately. It is debatable if we need to use additional substances to attempt to kill the mold or not, because without water, mold will not grow or reproduce spores.

Dry the Area as Soon As Possible

In our case, we had a leaking sink that needed to be dried out as soon as possible. Whatever the situation may be with mold or mildew growth, whether on walls, wood, clothing, in bathrooms, on furniture, concrete, etc., you need to dry out the surface to stop the mold from growing. For our sink situation we:

  • Shut off  Water – start drying process as soon as possible
  • Speed up drying process with a small heater
  • Removed the sink

We live in a very dry climate, so we had a head start on the drying part. As soon as the water was turned off and the dripping stopped, the area started to dry. I sped up the process by using a small heater under the sink.  After several hours, the entire sink and cabinet was very warm, not so warm that I was concerned about starting a fire, but if you use a heater, watch it very closely. I turned off the heater and in order to see the extent of the mold growth, I also removed the entire sink. Removing the sink also allowed the moldy areas to dry faster and more completely.

Mold Cleanup

After drying the area for about two days, the mold cleanup process was as follows:

  • Pressurized house with fan to blow any mold spores out the kitchen window
  • Soaked mold with alcohol and let dry, three separate times
  • Scrubbed the mold with detergent and water to clean
  • Used bleach in an attempt to whiten the mold
  • Painted the area to hide the black mold and to seal in any mold spores

Side Note: I do not know if it was necessary from a health standpoint or not, but since we have a whole-house window fan, and it only costs pennies per hour to run, I used it to pressurize the house and attempt to blow any mold spores out the kitchen window. For two days, the fan sucked in outside air from one window at low power (2,510 cubic feet per minute) and pushed all the air out the kitchen window. I let the area dry for several days. Since we live in very dry climate so that was probably overkill, humid climates will have a more difficult time drying the area.

Using Alcohol, Laundry Detergent and Bleach to Kill and Remove the Mold

There are a variety of substances that you probably already have at home that will kill mold including bleach, alcohol, vinegar, detergent, hydrogen peroxide, borax and tea tree oil, just to name a few of mold removal products. We may only be able to kill the part of the mold we see on the surface unless those substances can soak deep enough into the wood. I had some denatured alcohol on hand, so I used that to kill the mold. I poured the alcohol in a bowl and brushed it on with an old toothbrush (Fig. 1.). I held the bowl just underneath the counter top, so the alcohol dripped back into the bowl. I let the alcohol dry and repeated two more times.

mold removal using bleach and alcohol

Fig. 1 Mold Cleanup with 95% Alcohol. It was easy to scrub the black mold stain off the laminate after applying, but the fiberboard still looked the same.

After using the alcohol, the mold cleaned off the hard, laminated part of the counter top, but the mold looked the same as before on the rough fiberboard. I then scrubbed the area with water and laundry detergent. After that dried, it still looked the same. Apparently, mold can be easily scrubbed off of hard surfaces and can even be scrubbed off of the framing lumber, but from my experience, it can not be cleaned off the rough edge of fiber board. Removing mold stains from certain surfaces will be tougher than others and may require either replacement or covering with other applications such as paint.

I even used bleach on the edge of the fiber board to see if the area would bleach to a lighter color. There were a few places that did turn to a whiter color, but most of the area seemed not to be affected at all. Another myth bites the dust, bleach does not whiten black mold.  In the end, I simply painted the area to make it look better and to also seal in any remaining mold spores (Fig. 2.).

how to clean mold

Fig. 2. Mold area cleaned and painted.

Figure 2 was taken after putty was put down around the edge of the sink cutout in preperation for re-installing the sink. The prolonged wetness that allowed the mold to grow also left the thin part of the counter top in the back splash area very weak, so I supported it with an angle attached to the stud on the back wall. I intended to use two angles, 16 inches apart on different studs, but the one angle strengthened the area enough.

Now that the mold area was cleaned up, the next step was to replace the leaky faucet and put the sink back which we will cover in our next post.

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