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Posted on Oct 20, 2014

There is Mold in Your Coffee Maker

There is Mold in Your Coffee Maker

And you should clean it regularly.

We are serious about water.  As a close second, we are almost as serious about coffee. 12 people work in our Austin, Texas offices, yet we have two coffee makers.  We recently saw an article on the Huffington Post, which nearly made us spit out our second-favorite drink.  The article was called Your Coffee Maker Is Full Of Mold. Here’s How To clean It. The article quoted a National Sanitation Foundation (NSF) study finding half of all basic coffee makers had yeast and mold, and one-in-ten had coliform bacteria. If that wasn’t gross enough, the article went on to say on average, home coffee reservoirs had higher germ counts than both bathroom door handles and toilet seats.


Apparently, hot water isn’t enough to get the “yuck” out.  The article quoted Carolyn Forté, director of the Home Appliances and Cleaning Products Lab at the Good Housekeeping Research Institute, about the most effective way to clean your coffee maker. Forté suggested vinegar, which we rushed out to buy a gallon of, and use in the office.

“The carafe, lid and filter basket should be cleaned daily with warm, sudsy water,” Forté told The Huffington Post via email. “A coffee maker that’s used daily should be decalcified about once per month in hard water areas and every two to three months in soft water areas.”

Similar rules apply for “pod-based machines” like Keurigs – debris can clog their many nooks and crannies, so they also benefit from a vinegar run-through every few months, Forté says.

No matter how often you use them, these decalcifying steps (outlined here by Huffington Post for classic coffee makers) are the key to better-tasting, mold-free coffee:

  1. Fill the coffee maker’s water chamber with equal parts white vinegar and water. Using a paper filter, allow to brew until half the chamber is empty.
  2. Turn the coffee maker off and let it sit for 30 minutes, then finish brewing.
  3. Rinse the machine by using a new paper filter to brew a pot of clear water. Do this twice.
  4. Fill the carafe with warm, sudsy water and some rice as a gentle abrasive. Swirl the mixture in the pot, then use a scrubber sponge to remove any gunk. Rinse and dry.
  5. Wipe the outside of the machine with a damp cloth (this and the previous step should really happen every day).


We don’t have the carafe style of coffee maker in the office, we have a Keurig and a Nespresso machine (I told you we loved coffee.  I should have warned you we were also coffee snobs). Feeling really grossed out, I filled both of the machines water chambers with straight white vinegar and started running it through one cup at a time.  The office smelled like a pickle factory.  I got a lot of complaints.  Don’t these people care that I’m trying to save their lives?  Undeterred, I kept hitting “brew” until the vinegar was gone.  Then I filled each tank, twice, with tap water and ran that through.  I thought it was enough until my co-worker Chris made a cup of coffee.  As soon as she added the half-and-half it curdled.  The half-and-half was opened the day before, so we still had vinegar in the tank (this was confirmed when Chris took a sip- sorry Chris!).  I filled each water tank again and repeated the flushing.  I then made another cup of coffee and added half-and-half.  No curdling!  Chris skeptically accepted my peace offering and took a sip.  Although I curbed her want for a cup of coffee, she said the new cup tasted “fine”.  I consider that a success.  Low levels of mold in the coffee pot wouldn’t be detectable.


I now know our office coffee pots are clean, thanks to the vinegar induced, curdled half-and-half.  Just knowing that makes me feel like it now tastes better.  If you haven’t done so recently, clean your coffee maker.  And always use filtered water when you make your coffee.  I don’t know about you, but I’ll take curdled half-and-half in my coffee over mold and bacteria any day.


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