Wednesday, July 27, 2011

Mold - A Culture Inside Your Appliances

This past weekend, our dishwasher started leaking. By the time we noticed, a serious puddle of water accumulated under the dishwasher and started making its way toward the hardwood floors in the rest of the kitchen.

Unfortunately, I have experience with water damage causing mold in our home. We once had an irresponsible contractor who caused a water leak during remodelling and then somehow just “forgot” to mention it. By the time we were made aware of the leak (we were living in England at the time, trying to get this house ready for our return to the States), our kitchen was a disaster. The beautiful hardwood floors warped beyond repair and the sub-floor was covered in disgusting, potentially deadly black mold.

Given this experience, I knew that water leaking anywhere in my home is cause for alarm and so I went immediately into “urgent action mode” to prevent another major problem. First, I enlisted everyone in the house to soak up all the water with a stack of cheap towels we save for just such dirty, smelly occasions. We dried the interior and exterior of the dishwasher, our kitchen floor, and we tried our best to dry the puddle underneath the machine. Then, we focused a fan to the underside of the dishwasher to speed up evaporation of any remaining moisture that may have soaked into the wood sub-floor.

After those preliminary steps, I did what anyone who understands the serious risks of mold would do; I called for expert help. I have two experts who have saved our home in the past, Matt Sanders (with Ecostar) and Gabriel Peretti (with Zerorez). These guys are mold remediation and mold prevention experts. Matt Sanders saved our kitchen (and our home) by removing all the affected wood and drywall the disreputable contractor had damaged by the leak while we were in England. Gabriel Peretti saved our upstairs hardwood floor after a roof leak by literally vacuuming the water with a special pressurized system. What I learned from these experiences is that it is impossible to know how much moisture, and therefore mold danger, you are facing without proper measuring equipment. The good news is that you can often save your floors (or even your whole house) by having experts do the drying if the leak is severe and you act without delay.
Mold can lurk inside your walls, under your floors, and
can damage property beyond repair.

It was Friday afternoon and, to my relief, Matt answered his phone. His advice: keep the fan running for the weekend and he would come over on Monday to assess the moisture level of the sub-floor. Too much moisture or the wrong kind of sub-floor (particle board) and the wood would definitely need to be replaced. As promised, Matt came on Monday morning and he had great news. The sub-floor was not particle board, it was plywood, and the moisture level was very low after a weekend with the fan blowing on it. Apparently living with the racket of a fan going, at high speed, in my kitchen all weekend was worth it. Matt assessed that there was no danger of mold developing, due in no small part to my quick action.

Ironically, I recently found some new research about mold growing in household appliances, and we were working on just this post when my own dishwasher decided to misbehave. The truth is, I should have acted on what I learned. In our research we learned that it was important to clean the drains in dishwashers to prevent water from backing up and making a nice environment for mold to start enjoying your dishwasher. I think that by neglecting the drain in my own dishwasher, it may have become so clogged that it backed up, causing the puddle on my floor. To be fair, our dishwasher is ancient and probably due for replacement some time ago.

So my mold prevention advice from this experience is twofold. First, don’t neglect cleaning your drains/filters. Second, find the best mold prevention and mold remediation experts in your area and keep them on speed dial.

If you live in the United States, you can contact the organization that Matt and Gabriel recommend, the Carpet and Fabricare Institute. On their website you can find a local professional who is qualified and knowledgeable. If you live outside the United States, you may want to contact the Carpet and Fabricare Institute to find our whether there is a reputable association in your country that can help you find qualified experts. Best of all, if you are fortunate enough to live in Southern California, you should get to know Gabriel and Matt; they won’t let you down.


So, back to my research into appliance mold. My interest piqued in this topic when I heard about a recent study in the journal Fungal Biology. In the study, researchers found that most household appliances do eventually develop mold. It turns out that the conditions inside most appliances are almost perfect for mold to take up residence and thrive. We decided to find out more about this problem and to educate our readers about how to prevent and treat mold in their appliances. Unfortunately, the importance of the lessons we learned came to haunt me through my own dishwasher disaster before I had an opportunity to take preventative action in my own home.

When you think about it, our homes are a veritable all-you-can-eat buffet for mold. Mold needs only 5 things to grow: moisture, “food” (organic matter), darkness, oxygen, and warmth. There are many places that at least 4 of these triggers occur. Similar to an infomercial, if you “just add water” to these locations, any mold spores there will start to grow. Where do these triggers typically occur, and how can we reduce them?
Mold needs organic matter to grow.
  • Water -- humidity (over 55% in the air is enough), condensation, and water leaks are the most common sources. Humidity of this level can come from the environment (especially this time of year) or from long, hot showers. Condensation occurs frequently in air conditioning units.
  • Warmth -- our homes are kept suitably warm to benefit many species (humans, dogs, cats, etc.), which is also quite agreeable to mold.
  • Darkness -- basements, attics, closets, spaces between walls, cabinets, drawers.
  • “Food” -- Molds grow through the decay of organic matter. This can happen in dust, dander, actual food, wood, drywall, wallpaper, carpet (including liners), curtains, plant matter, or dirt


Washing Machines
  • Mold is found most commonly in front loading machines, but any style of washer can be affected. The areas of concern are the plastic/rubbery area (the gasket) where the door meets the body of the machine. 
  • If you have mold in your washer it causes clothes to smell unclean or like mildew, despite being freshly laundered.
  • Using too much soap -- leftover suds create a lot of surface area upon which mold can easily grow. Front loading washing machines need and effectively use far less soap than their top loading cousins. By adding increasing amounts of soap in an attempt to combat the increasing smell of mildew and mold, you only make the problem worse.
  • After a wash cycle, small amounts of leftover water may remain in the machine. Leaving the machine door closed after use and between cycles provides darkness and maintains warmth, both of which mold uses to prosper.
  • Dirty drain pump filter -- manufacturers say this should be cleaned monthly to remove dirt, lint, and skin, among other substances (mold grows on dead organic matter). 
Ways to clean:
  • Mix water, vinegar, baking soda and scrub affected areas. Then, spray undiluted vinegar on hard to reach areas. After the vinegar sits for a little while, rinse with water
  • Run the “Clean Washer” cycle found on newer machines. (add 2 cups vinegar to the basin, run on hottest water setting)
  • Check your washing machine manual for information on how to clean the drain pump (and other) water filters in the machine, and do so regularly. Unfortunately, no matter how well you clean the basin, if you have a colony of mold in the areas where water comes into (or backs up on its way out of) the area your clothes go, it will spread to your clothes.
  • Dry the rubber gasket where the door meets the body of the machine, this is the most common place where mold develops and grows (mold likes rubber much better than stainless steel or other metals).
  • Consider wiping down the interior to remove leftover water  
  • Don’t let dishes sit for any considerable length of time after the cycle is over.
  • Leave the door open for a while after use to allow air to flow and for any excess moisture to clear.
  • Clean the drain at the bottom of the basin.
Air Conditioners
  • Clean the condenser coils regularly as water condenses and collects there.
  • Make sure that if your A/C machine has a drip pan (where water from the coils is collected) that water is not allowed to stagnate there. The pan should be at a slope that allows the water to easily flow to an appropriate drain. This drip pan should also be cleaned periodically with a disinfectant.
  • Check and replace the filter on a regular schedule. HEPA filters will collect almost all mold spores as cold air is circulated and are an excellent choice for reducing airborne contaminants overall.
Coffee Machines
  • Mold develops most commonly if the used coffee filter is not promptly removed.
  • Mold in a coffee maker.
  • Clean by running the machine with undiluted white vinegar in place of water (may take several cycles) and then run with just clean water.


Good ideas to follow in all your appliances:
  • Wipe down any gaskets after each use (the rubbery parts around the doors) to remove water.
  • Leave appliance/machine doors open whenever possible for at least a few hours after use to allow any moisture to evaporate.
  • Soap or even hot water is not enough to kill these extremophile organisms (mold and bacteria that can survive almost anything). They have developed resistance to the temperatures and chemicals used in their “home” appliances. As they adapt further, the only way to properly clean these appliances may be to use vinegar to remove them. 
  • Avoid using too much soap as this can actually help mold to start growing.
  • Consider using an air purifier with a HEPA filter and UV sanitizing light, as these are able to capture and eradicate (or irradiate) mold spores and other toxic substances associated with mold.
  • Clean the drain pump (and other) water filters in the machine. It may sound like a pain, but if you happen to have a colony of mold on the filter or in the drain pump where water comes into (or backs up on its way out of) your machines, it will spread to anything inside. Of course, you could choose to just replace your appliances every six months and then you need not worry.
  • Use Borax (boric acid) to absorb any residual moisture or when storing unused appliances for long periods of time. Boric acid absorbs moisture and kills off mold by starving it of moisture.
  • Place a fan (for about 2 hours) in any area with excess moisture. This can help prevent mold from forming. You don’t want to leave the fan running for more than 2 hours because you may be aiding in the spread of mold spores from other places inside or outside of your home. Realize that mold spores are everywhere in our environment and we can’t get rid of them all. The goal is to limit the introduction and overgrowth of dangerous types of mold.

Not all molds are dangerous.


Mold remediation companies offer many different types of treatments to remove mold. These can range anywhere from simple detergent solutions all the way up to physical removal (and replacement) of large parts of your house. It is important to discuss the possible options and carefully consider which is appropriate for your situation.

It is important to aggressively prevent and treat mold immediately as it could lead to all kinds of health problems. Mold contamination is a serious health hazard. While not all molds are toxic to humans, some of them can be deadly, especially if you have other health conditions. If you suspect mold contamination, then make sure you have a responsible and responsive mold remediation company on speed dial. The sooner you take action, the less time mold has to spread. Keeping whatever contamination is present to a minimum will cost you less both in terms of cost of removal and also potential health problems.

Researched and written by Dr. Rebecca Malamed, M.D. with assistance from Mr. Malcolm Potter.


  1. This was such an eye opener. My washing machine (only 4 years old) and dishwasher were full of visible mold. I would have never thought to look in the rubberized parts. Thank you for keeping my family healthy!

  2. Wow... Moving into a new home, I never thought of mold being present. Little did I know, I brought it with me. Thank you for the tips on the washers, having 8 boys my washer is constantly in use. I use the method you suggested here once a week, and the clothes seem to be fresh again. Tips also helped with our dishwasher. Much appreciate your sharing...

  3. Thanks so much for walking me through the step-by-step process of mold remediation. As much as I hate mold, I’m always hesitant to let strangers into my home to spread around strange chemicals. A guide like this is really helpful.

    According to me one of the hardest things to do is pull out mold, mildew and gunk from in between the tiles in the bathroom. It is necessary to hire the services of professional mold removal companies as they know the best and easiest way to remove you mold permanently.


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