I Hate To Break It To You, But Your Coffee Maker Is Probably Growing Mold

Every night before bed I prep my coffee for the next morning. I lovingly fill the glass pot and pour it into the reservoir. I fight with the filter and count out the scoops of coffee grounds, lamenting the mess I usually make, but patting myself on the back for being so forward-thinking. Exhaustion and cranky kids demanding breakfast will have nothing on me before sunrise. This night-before routine means I am less stabby because fresh, hot coffee is waiting for me with the press of a button.

But apparently bacteria, yeast, and mold are also waiting for me because nothing is sacred, and I guess I am not allowed to have nice things.

A study done by NSF International, formerly known as the National Sanitation Foundation, examined kitchen products and found that half of the sampled reservoirs in coffee makers—the old fashioned, Mr. Coffee basket and carafe kind like I use—had yeast or mold. How could that stuff build up? I use my machine all of the time; surely mine is fine. Well, probably not. And yours is probably gross too so don’t be smug.

But it’s not that terrible, right? We have all taken a bite of moldy bread or food and lived to tell about it. However, deeper examination showed that home coffee reservoirs, on average, had more germs than what are found on both toilet seats and bathroom door handles. Since I am not accidentally licking bathroom surfaces, this seems to have crossed into WTF territory.

Those single-serve Keurig and Nespresso machines are not immune to gag-worthy morning microbes either. Depending on how quickly you go through coffee pods, water could sit stagnant for days in the reservoir before use. Lisa Yakas, senior product manager of Consumer Products at NSF International suggests dumping any unused water out at the end of each day and letting the container thoroughly dry.

I guess it makes sense. Germs and mold grow well in moist, dark places and while coffee makes my dark soul a bit lighter, the pot that it is brewed in is perpetually damp. I take my coffee pot for granted and don’t care for it the way it takes care of me. Pollen and dust collects on the top; splatter and grounds gather at the base, and the glass carafe is stained. I knew I was kind of messy, but I didn’t realize I was encouraging a petri dish of infections waiting to happen. Folks with allergies can be especially sensitive to the microorganisms growing on and around the coffee pot too. Yes, around.

If the inside of your coffee pot is gross, you would be foolish to think the outside is not. The handle is touched all day long by you and anyone else who fills their mug. And if you share office space, the germiest place in the building is the break room. People are touching the tops of coffee pods, mugs, and filters all day long, and increasing the likelihood that you will be stirring E. coli and fecal matter into your coffee along with your creamer. Yes, I said fecal matter. Caffeine is not the only substance entering your system during your afternoon coffee break. Shit.

Even if everyone is washing their hands properly and attempting to keep the space tidy, if the counters, sink of mugs, or coffee pot are being cleaned with an old sponge, aka, “fecal germ bombs” then clean is an illusion. And let us not forget about the floating bacteria from the bathroom because someone didn’t or couldn’t close the lid before flushing. This phenomenon is called the “toilet plume” and happens when a toilet is flushed. Germs, fecal matter, and bacteria can shoot up to 15 feet in the air and travel beyond the bathroom. My old officemate may have been the worst part of a previous job, but this information is making it hard to decide.

I am glad I work from home, but my kitchen isn’t as sanitary as I would like to think it is. One study found that 44% of sinks and sponges are home to fecal bacteria. If and when I clean the glass coffee carafe of my coffee maker, I have a feeling I am just swirling around bacteria and transferring it from one object to another in the name of cleaning.

Kelly Reynolds is a germ specialist who studies household germs at the University of Arizona and says that our bodies are built to deal with these household germs, but warns that at a certain point, the levels will increase enough to make us sick. The heat from the brewing process can kill some of the germs, but we all need to be more proactive in cleaning—really cleaning—our coffee makers.

The best bet is to follow the manufacturer’s cleaning directions, but common sense and intention will go a long way. It’s embarrassingly obvious, but cleaning my coffee pot daily with warm, soapy water and then letting it air dry will reduce the chance for germs to settle in and spread. And since I use my coffee maker daily, I should be decalcifying it about once a month. Vinegar is an inexpensive and safe way to do this. It will clean out most of the yeast and mold, but, even though it is a natural disinfectant, it won’t kill all types of bacteria. When it’s not in use I need to be sure to air out all of the parts and use cloth instead of a sponge to clean.

Did I clean my coffee maker after learning all of this? Yes. I ran a 50/50 blend of vinegar and water through my pot, stopping it for 30 minutes halfway through brewing to allow things to clean themselves. After letting the mixture run all the way through the pot, I brewed another pot of plain water to get rid of the vinegar residue. Will I keep up this routine? Yes? I hope so. My coffee tasted better and I am healthier for it.